THE UNITED STATES 
STRATEGIC BOMBING SURVEY 
The Effects 
of 
The Atomic Bomb 
on 
Hiroshima, Japan 
Volume I 
Physical Damage Division 
Mfly. 1947 THE UNITED STATES 
STRATEGIC BOMBING SURVEY 
The Effects 
of 
The Atomic Bomb 
on 
Hiroshima, Japan 
Volume I 
Physical Damage Division 
Dates of Survey: 
14 October-26 November 1945 
Date of Publication: 
May 1947 This report was written primarily for the use of the U. S. Strategic Bombing 
Survey in the preparation of further reports of a more comprehensive nature. Any 
conclusions or opinions expressed in this report must be considered as limited to the 
specific material covered and as subject to further interpretation in the light of further 
studies conducted by the Survey. 
This document contains information affecting the national defense of the United 
States within the meaning of the Espionage Act, 50 U. S. C., 31 and 32, as amended- 
Its transmission or the revelation of its contents in any manner to an unauthorized 
person is prohibited by law. 
This report will not be reproduced in whole or in part or distributed to any agency 
or person other than those to whom original distribution is made without the approval 
of The Director of Central Intelligence, Washington, D. C. 743149 opo FOREWORD 
The United States Strategic Bombing Survey 
was established by the Secretary of War on 3 
November 1944, pursuant to a directive from the 
late President Roosevelt. Its mission was to 
conduct an impartial and expert study of the 
effects of our aerial attack on Germany, to be used 
in connection with air attacks on Japan and to 
establish a basis for evaluating the importance and 
potentialities of air power as an instrument of 
military strategy for planning the future develop- 
ment of the United States armed forces and for 
determining future economic policies with respect 
to the national defense. A summary report and 
some 200 supporting reports containing the 
findings of the Survey in Germany have been 
published. 
On 15 August 1945, President Truman requested 
that the Survey conduct a similar study of the 
effects of all types of air attack in the war against 
Japan, submitting reports in duplicate to the 
Secretary of War and to the Secretary of the 
Navy. The officers of the Survey during its 
Japanese phase were: 
Franklin D’Olier, Chairman. 
Paul H. Nitze, Henry C. Alexander, Vice 
Chairmen. 
Harry L. Bowman, 
J. Kenneth Galbraith, 
Rensis Likert, 
Frank A. McNamee, Jr., 
Fred Searls, Jr., 
Monroe E. Spaght, 
Dr. Lewis R. Thompson, 
Theodore P. Wright, Directors. 
Walter Wilds, Secretary. 
The Survey’s complement provided for 300 
civilians, 350 officers, and 500 enlisted men. The 
military segment of the organization was drawn 
from the Army to the extent of 60 percent, and 
from the Navy to the extent of 40 percent. Both 
the Army and the Navy gave the Survey all possi- 
ble assistance in furnishing men, supplies, trans- 
port, and information. The Survey operated 
from headquarters established in Tokyo early in 
September 1945, with subheadquarters in Nagoya, 
Osaka, Hiroshima, and Nagasaki, and with mobile 
teams operating in other parts of Japan, the islands 
of the Pacific, and the Asiatic mainland. 
It was possible to reconstruct much of wartime 
Japanese military planning and execution, engage- 
ment by engagement, and campaign by campaign, 
and to secure reasonably accurate statistics on 
Japan’s economy and war production, plant by 
plant, and industry by industry. In addition, 
studies were conducted on Japan’s over-all stra- 
tegic plans and the background of her entry into 
the war, the internal discussions and negotiations 
leading to her acceptance of unconditional sur- 
render, the course of health and morale among the 
civilian population, the effectiveness of the 
Japanese civilian-defense organization, and the 
effects of the atomic bombs. Separate reports will 
be issued covering each phase of the study. 
The Survey interrogated more than 700 Japa- 
nese military, government, and industrial officials. 
It also recovered and translated many documents 
which not only have been useful to the Survey, 
but also will furnish data valuable for other studies. 
Arrangements have been made to turn over the 
Survey’s files to the Central Intelligence Group, 
through which they will be available for further 
examination and distribution. ACKNOWLEDGMENT 
This present report was prepared by the Physical Damage Division of the 
Survey. The Division officers for the Japanese phase were: 
Harry L. Bowman, Director. 
Lt. Col. Charles R. Chapman, Chiej. 
Maj. Leland N. Stead, Executive. TABLE OF CONTENTS 
Volume I: Page 
Introduction 1 
Reference tables : 2 
Section I. Object of study . _ 5 
II. Summary 7 
Appendix A. Photo summary 30 
III. General information. 60 
IV. The target. 64 
V. High-explosive attacks on Hiroshima . 80 
VI. The atomic-bomb attack 83 
VII. Determination of air zero 91 
VIII. Typical Japanese dwellings 96 
Volume II; 
Reference tables. 
Section IX. Fire—cause and extent. 
X. Damage to buildings. 
Appendix A. Buildings 1-135. 
Volume III: 
Reference tables. 
Section XI. Damage to machine tools. 
XII. Damage to bridges. 
XIII. Damage to services and utilities. 
XIV. Damage to stacks. 
XV. Photo interpretation. 
Note.—A table of contents for each volume and each section is provided in the forepart 
thereof. 
V Figure 1 
VI INTRODUCTION 
1. The news of the detonation of the atomic 
bomb over Hiroshima, Japan, shortly after 0800 
on the morning of 6 August 1945, was the first 
intelligence, other than veiled hints, to reach the 
nations of the world that a nuclear-fission weapon 
of destruction was in the hands of one of the 
warring powers. People in general were stunned. 
Reactions at first were almost hysterical; all sorts 
of dire prophecies came from the press, the pulpit, 
and statesmen; modern methods of warfare had 
become overnight, as it were, totally ineffective 
and obsolete; no form of protection nor counter- 
measures against the bomb could ever be devised; 
in short, the atomic bomb heralded the end of one 
phase of civilization and initiated a new one, con- 
cerning the manifestations of which no one was 
imaginative or daring enough to hazard a logical 
guess. 
2. As time elapsed and opportunity was had to 
make dispassionate and scientific appraisals, the 
picture began to emerge in its true perspective 
with the result that many of the early and emo- 
tional judgments have been modified and even 
completely changed. Just recently, preliminary 
reports of the Bikini tests have served to temper 
even further the first portentous reactions. 
3. Study and further experimentation will 
together point to what is to be done in the future 
to counteract the effects of the atomic bomb. In 
the meantime any and all information regarding 
the bomb’s characteristics, behavior, and effects on 
life, morale, industry, business, utilities, and all 
aspects of economic endeavor is extremely im- 
portant to military and civilian planners in their 
efforts to evaluate the bomb and to provide 
efficacious countermeasures. 
4. As soon as it was considered reasonably safe 
to enter the city of Hiroshima, numerous investi- 
gations, covering all phases of the atomic bomb’s 
destructive forces, were undertaken by different 
agencies. This report is the result of only one of 
those investigations. In it no attempt is made to 
pass judgment on the over-all effectiveness of the 
atomic bomb, its purpose being only to tell as 
complete a story as possible of the physical 
damage suffered by the stricken city as results of 
both the direct and indirect effects of the bomb’s 
detonation. Reports of damage to buildings of all 
existing types—industrial, commercial, and resi- 
dential—are included herein, together with some 
conclusions concerning the relative degrees of 
resistance inherent in the several types to the 
direct and indirect results of the atomic-bomb 
forces. Likewise, there is considerable discussion 
regarding building contents’ vulnerability and 
degree of damage in relation to the types of con- 
struction. Fire also is reported on at length since 
it resulted from both direct and indirect causes and 
was responsible for a large proportion of the 
physical damage* Other subjects studied and 
reported on are: damage to machine tools, bridges, 
stacks, services, and utilities. In each case, when 
possible, pertinent remarks, conclusions, and rec- 
ommendations are incorporated in the appropriate 
sections. 
5. A similar complete physical damage report 
on Nagasaki, the scene of the dropping of the 
second atomic bomb on 9 August 1945, will be 
found in Physical Damage Division Report 70. 
1 REFERENCE TABLES 
TYPES OF DAMAGE 
Damage to Buildings, Industrial and Domestic. 
a. Structural: Damage to principal load-carry- 
ing members (trusses, beams, columns, load- 
bearing walls, floor slabs in multistory buildings) 
requiring replacement or external support during 
repairs. Light members such as purlins and 
rafters are not included. 
b. Superficial: Damage to purlins and other 
light members, stripping of roofing and non-load- 
bearing exterior walls. Damage to glass and 
interior partitions not included. 
Damage to Machinery, Utilities and Equipment, 
a. Total: Not worth repair. 
h. Heavy: Requiring repair beyond capacity of 
normal maintenance staff, usually returned to 
manufacturer. 
c. Slight: Requiring repair within capacity of 
normal maintenance staff. 
Damage to Contents Other Than Machinery and 
Equipment. 
a. Total: Not usable. 
b. Other: Usable if reprocessed or repaired. 
2 Table A.—Building types or classifications 
(Tables A and B from Joint Target Group] 
Group 
Type 
symbol 
Description 
A. 
Single-story, no traveling 
1. 
With saw-tooth roofs 
Al. 1 
All buildings of this group with saw-tooth roofs 
cranes, spans generally 
less than 75 feet, heights 
other than those included in Types A1.2, A1.3, 
and A1.4. 
at eaves generally less 
Al. 2 
Frame and roof slab of monolithic reinforced 
than 25 feet, area of 
concrete. 
10,000 square feet or 
Al. 8 
Exposed top chords of trusses. 
more. 
Al. 4 
Stressed-skin type of reinforced concrete (e. g. 
Zeiss Dywidag). 
2. 
Without saw-tooth roofs_ 
A2. 1 
A2. 2 
A 2. 3 
A2. 4 
A2. 5 
Simple beam and column. 
Arches and rigid frames. 
Truss construction. 
Frame and roof slab of monolithic reinforced 
concrete. 
Stressed-skin tvpe including concrete shell. 
B. 
Single-story with travel- 
ing cranes; any length 
of span; area of 10,000 
square feet or more. 
1. 
Buildings housing heavy 
cranes. 
B1 
Buildings containing runways for heavy cranes 
(capacity 25 tons or more); height at eaves 
generally more than 30 feet. 
2. 
Buildings housing light 
cranes. 
B2 
All buildings in this group other than those in Bl. 
C. 
Single-story; no traveling 
crane runways; spans 
greater than 75 feet; 
height at eaves gener- 
ally greater than 25 
feet; area of 10,000 
1. 
Main frame members in 
2 directions. 
Cl. 1 
Cl. 2 
Roof trusses supported along one side of building 
by long span trusses and along other side by 
columns. Permits large door along one side 
and at ends. 
Continuous trusses in one or two directions; long 
span in one direction, supported by columns 
square feet or more. 
or exterior walls and bv internal columns. 
Cl. 3 
Cl. 4 
Exposed chord saw-tooth roof buildings; exposed 
chord trusses supporting major size trusses at 
90°. One or both truss systems may be of long 
span. 
Diamond mesh arch. 
2. 
Main frame members in 
one direction only. 
C2. 1 
C2. 2 
C2. 3 
Long-span arches, individually supported along 
sides of building. May be arranged in multiple 
spans joined along side. 
Long-span, triangular or bowstring trusses, indi- 
vidually supported by columns at sides of 
building. May be arranged in multiple spans 
joined along side, using common columns. 
Roof pitch exceeds 2 in 10. 
Long-span trusses, top cord of pitch 2 in 10 or 
less, including exposed cord saw-tooth roofs, 
individually supported by columns along sides 
of building. May be arranged in multiple 
spans using common columns or may be con- 
tinuous over internal columns. 
3. 
Shell-type construction _ _ 
C3 
Stressed-skin including concrete shell construc- 
tion. 
D. 
All single-story buildings 
of less than 10,000 
square feet plan area. 
D 
This type covers all single-story industrial build- 
ings, regardless of type of construction if under 
10,000 square feet in plan area. 
E. 
Multistory, frame build- 
ei 
Earthquake-resistant; extremely heavy steel re- 
ings. 
inforced-concrete, multistory construction, de- 
E2 
signed to resist heavy lateral loads. 
Structures in this group other than those in El. 
F. 
Multistory, wall-bearing 
buildings. (May have 
internal columns.) 
FI 
F2 
Earthquake-resistant, wall-bearing construc- 
tion. (Walls of brick, reinforced concrete, or 
very massive masonry.) 
Structures in this group other than those in FI. 
8. 
Special Structures 
S 
Coke ovens, test cells, fuel storage, boilers in 
power plants, etc. 
Table B.—HE vulnerability classes 
HE vulnerability 
class 
Substructural groups 
(symbols refer to table A) 
HE vulnerability 
class 
Substructural groups 
(symbols refer to table A) 
VI 
El. 
V4 
Al, 1. A1.2, A1.3. A2.1, A2.2, A2.3, A2.4, 
V2 
HI, B2. 
D. 
V3 
E2, FI. 
V4A 
Cl.2. Cl.3, Cl.4, C2.3. 
V3A 
F2. 
V5 
A 1.4, A2.5, Cl.l, C2.1, C2.2, C3. 
3 FIRE CLASSIFICATION—BUILDINGS AND CONTENTS 
C—Combustible: Buildings whose roofs and/or walls are 
constructed of combustible material. The floors 
(except the ground floor) are required to be of 
similar construction. Wood-frame buildings with 
noncombustible sheeting on roof and/or walls are 
also included in “combustible” class. 
N—Noncombustible: Buildings which have no significant 
amount of combustible material in the structure, 
but whose structure is susceptible to damage by fire 
in the contents. An example of this type is a build- 
ing with exposed steel members which may be 
warped irreparably by the heat of a fire. Roofs of 
this type are: corrugated asbestos, corrugated iron, 
pre-cast or pour-in-place cement or gypsum on ex- 
posed steel and reinforced concrete 2% inches thick 
or less. 
11— Fire-resistive: Buildings which have no significant 
amount of combustible material in the structure and 
which will withstand all but the most intense fire 
without structural damage. Roofs and floors 
(other than ground) should be of concrete more than 
2)4 inches thick, and the steel fiame should be 
protected and not subject to ordinary fire damage. 
C and N, N and R, or C and R used where above types are 
combined in a single fire division. SECTION I 
OBJECT OF STUDY 
Page 
General 6 
Specific fi 
Other factors 6 
New effects 6 
Photographic intelligence 6 1. General 
The over-all objective of Physical Damage 
Team 1 was the collection, analysis, and evaluation 
of data pertaining to damage caused by tin1 
explosion of the first atomic bomb. 
2. Specific 
More specifically, matters of primary interest 
were the causes and extent of damage to structures, 
equipment and contents of domestic, commercial, 
industrial, and military installations. Accordingly, 
the following subject groups for study are estab- 
lished: 
a. First Priority. 
(1) Damage to Buildings. 
(2) Damage to Bridges. 
(3) Damage to Services and Utilities. 
h. Second Priority. 
(1) Damage to Machine Tools. 
(2) Damage to Stacks. 
3. Other Factors 
Precise findings regarding the effects of the 
atomic-bomb attack on structures and contents 
were found to be dependent on determinable facts 
relating to both the target and the attack. It was 
therefore essential in damage assessment and 
evaluation to consider such factors as (a) the 
cause and extent of fire; (6) history of high- 
explosive bomb attacks on the city; (c) locations 
of zero points; and (d) types of Japanese struc- 
tures. Of these four items, fire was unquestionably 
the most important and field investigation thereof 
yielded interesting and significant data. 
4. New Effects 
The release of atomic energy in Hiroshima 
presented a subject of such magnitude that it was 
impossible for a small group of investigators in a 
short period of time to develop and assimilate all 
the evidence available, particularly that which 
was applicable to new effects and their significance 
with relation to physical damage. An effort was 
therefore made to assemble: 
a. All available evidence on the phenomena re- 
sulting from the almost instantaneous release of 
an unprecedented amount of energy radiated over 
wave lengths from those beyond the heat bands of 
the infrared, through the visible spectrum and 
into the short wave lengths of the gamma rays. 
Information on these new effects came from obser- 
vation of flash burns on materials and persons, 
from stories of eye witnesses and from official 
reports. 
b. Data on the similarities and differences be- 
tween the atomic bomb and the conventional high- 
explosive and incendiary bombs with respect to 
physical damage. 
5. Photographic Intelligence 
As a pertinent allied subject, the technique, 
evaluation, and assessment of damage by means 
of aerial photos, plus the characteristics of atomic- 
bomb damage as seen from the air, were considered 
in relation to the actual facts determined by field 
study, in order that appropriate changes in inter- 
pretation to attain greater accuracy might be 
effected. SECTION II 
SUMMARY 
Page 
Part A. Foreword- _ __ 8 
B. Introduction 8 
C. The target _ _ 9 
D. The atomic-bomb attack.. _ _ 10 
E. Zero points 11 
F. Japanese buildings 11 
G. Cause and extent of fire. • 13 
II. Damage to buildings _ 16 
I. Damage to machine tools 18 
J. Damage to bridges 18 
K. Damage to services and utilities 21 
L. Damage to stacks 26 
M. Probable effects on other targets 26 
N. Photographic intelligence 28 
Appendix A. Photo summary.. . . 30 A. FOREWORD 
1. General 
The survey of Hiroshima was started on 14 
October 1945 and completed on 26 November 
1945. The over-all objectives were the collection, 
analysis, and evaluation of (1) data pertaining to 
physical damage caused by the detonation of the 
first atomic bomb used as a military weapon, and 
(2) data on the similarities and differences between 
the atomic bomb and the conventional high- 
explosive and incendiary bombs with respect to 
physical damage. Except where judged pertinent 
to the report, no study was made of other aspects 
of the atomic bomb relating to medical measures, 
morale, and civilian defense. 
a. The complement of Physical Damage Divi- 
sion Team 1 comprised 15 officers, 7 enlisted men, 
and 1 civilian. Attached to the regional head- 
quarters at Hiroshima were 4 officers and 11 en- 
listed men who had charge of supplies and rations, 
transportation, photography, and intelligence. 
Personnel were drawn from the Army and Navy 
as shown in the following table: 
many people who had fled to the hills immediately 
after the explosion had returned to the city and 
were busy erecting flimsy wooden and corrugated- 
iron shelters on the sites of their former homes. 
These new structures scattered over the city added 
somewhat to the difficulties of gathering data, but 
the returned inhabitants were of some assistance. 
Since almost all records in the city proper had 
been burned or otherwise destroyed by the atomic- 
bond) effects, or lost in the subsequent storms, 
these people supplied valuable information in 
tracing specific persons and segregating types 
of damage. 
d. This summary is a presentation of factual 
material based on a study and analysis of all 
reliable data gathered in the field and used in the 
preparation of Physical Damage Division Re- 
port 69. 
e. Other studies were conducted by the British 
Mission to Japan and by a team from the Bureau 
of Yards and Docks, United States Navy, both of 
which operated under the Physical Damage 
Division of the United States Strategic Bombing 
Survey. A separate report is being prepared by 
each of these investigating agencies. 
B. INTRODUCTION 
1. Highlights 
At 0816 hours 6 August 1945, one of three 
B-29s over Hiroshima dropped the first atomic 
bomb ever used for military purposes. An eye- 
witness who was 2y2 miles west of the city stated: 
I saw a single enemy airplane flying over Hiroshima. 
It dropped or fired a brilliant object. 1 thought at first 
that it was an incendiary bomb, but then I saw what 
looked like a smoke ring from a funnel, gradually falling 
toward the ground. It grew larger almost immediately 
and increased in brilliance and soon covered an area almost 
as big as the city. A flame appeared which was even 
brighter than the sun, I thought I might get hurt so I 
fell flat on the ground. 
Exploding in the air 2,000 feet above a post 
office slightly northwest of the heart of the city, 
the atomic bomb achieved an intensity unpar- 
alleled in the history of destruction by a single 
man-made weapon. As estimated and described 
by scientists the nuclear-fission bomb had changed 
into a fireball hotter than the center of the sun 
(70,000,000° C.) during the detonation that was 
over in a millionth of a second. It emitted 
radiations ranging from beyond the heat bands of 
infrared, down through the visible spectrum and 
USSBS personnel assigned to Hiroshima 
Physical damage 
team I 
Regional headquarters 
Army 
Navy 
Total 
Army 
Navy 
Total 
Ag- 
gre- 
gate 
Officers 
4 
11 
15 
2 
2 
4 
19 
Enlisted Men 
1 
6 
7 
8 
3 
11 
18 
1 
1 
1 
6 
17 
23 
10 
5 
15 
38 
b. The team made a field examination and 
inspection of buildings, machine tools, bridges, 
utilities, services, and stacks; gathered statistical 
and documentary material, including Japanese 
accounts of the atomic-bomb attack and Japanese 
damage assessments; and conducted hundreds of 
interrogations and interviews of virtually all the 
surviving city and prefectural officials. Through 
eyewitness stories, observations of flash-burns on 
persons and materials and cooperative work with 
other teams, considerable information, in addition 
to the above, was gained in connection with new 
effects, i. e., the phenomena resulting from the 
detonation of a nuclear-fission bomb. 
c. By the time the team arrived in the field, 
8 into the ultraviolet and penetrating gamma rays. 
The radiations were of an intensity without prec- 
edent in human experience. Pressures developed 
in the bomb were of the order of a thousand 
billion times atmospheric pressure. 
2. Effects 
The paralyzing results of the explosion were as 
unique and spectacular as the bomb itself. 
a. Buildings. Approximately 60,000 of 90,000 
buildings over an area of 9.5 square miles were 
totally or severely damaged. Roofs and walls 
were stripped from other buildings 4 miles from the 
explosion and glass windows were broken up to 8 
miles. 
h. Machine Tools. Practically all machine tools 
were totally or heavily damaged by ensuing fire 
over an area exceeding 4 square miles; were 
damaged in varying degrees by fire, debris, and 
exposure over an irregular 9-square-mile area; 
and, except where shielded, were subject to expo- 
sure damage over a 50-square-milc area of 4-mile 
radius. 
c. Fires. Radiant heat from the bomb and by 
overturned charcoal stoves, electric short circuits, 
and other sources of ignition developed a confla- 
gration which consumed all combustible material 
over an area of 4.4 square miles and overwhelmed 
what survived of the fire-fighting forces. 
d. Public Utilities. All utilities and services 
were disrupted and damaged, a great many key 
employees were killed or wounded, and the city 
was temporarily without transportation, electric- 
ity, telephonic communications, gas, water, or 
sewers. 
e. Stacks. Within a radius of 1.6 miles from the 
point on the ground directly below the point of 
air-burst (ground zero) 45 percent of all stacks 
were damaged beyond use. 
j. Bridges. Of 81 important bridges scattered 
over the city’s 26.5 square miles, 33 percent of 
those constructed of wood were totally damaged 
blast and fire, but those of concrete and steel 
construction were not seriously damaged. The 
entrances and exits of the bridges were clogged 
with debris from the adjacent collapsed and burn- 
ing buildings, temporarily trapping the victims 
on the islands without hope of immediate escape 
to, or relief from, the outside. Thirty hours 
elapsed before the first rescue and relief party 
penetrated the stricken area. 
g. Casualties. The dead were estimated at 
70,000, with an equal number injured. 
C. THE TARGET 
1. The City 
Beginning as a small fishing village in 1591, 
Hiroshima (lat. 34°24' N., long. 132°28' E.), 
located in the southwestern area of the principal 
Japanese Island of Honshu and on the north- 
western corner of the important Inland Sea, had 
developed into an important, modern, adminis- 
trative, communications, and military center. 
The seventh largest city in Japan, it had had a 
wartime peak population of 380,000, but five 
completed evacuations and a sixth in progress 
had reduced this figure to an estimated 245,000 
by 6 August 1945. The city was built principally 
upon the fan-shaped alluvial deposits of the Ota 
River which flowed to the Inland Sea down one 
of the few valleys running from southwest to 
northeast across the Chugoku mountain range. 
The river, crossing the delta by six channels, 
divided the city into seven fingerlike islands. 
Except for four small, rocky formations, only 
one of which was as much as 220 feet high, the 
delta was uniformly flat and about 10 feet above 
sea level. By dredging and filling, the natural 
deltaic islands had been extended to provide 
land for the growing city. Circled on the west 
and northeast by a chain of hills 150 to 1,100 
feet high, the Hat, evenly exposed area stretched 
6,500 feet in all directions from the heart of the 
city over the scattered islands and onto the main- 
land. Within the city boundaries Hiroshima 
covered approximately 26.5 square miles. 
a. Built-upness. Densely (over 40 percent plan 
area) or moderately (20 to 40 percent plan area) 
built-up areas extended for 23,000 feet on the 
north-south axis and 17,000 feet east-west. 
Around the heart of the city in a concentric area 
with a minimum radius of 6,000 feet occurred the 
greatest density of dwellings and wood-frame 
buildings. In addition, within this area were 
located many load-bearing, brick-wall buildings, 
fewer steel-frame structures, and at least 50 
multistory, reinforced-concrete buildings which 
were representative of the post-1923, earthquake- 
resistant design. Interspersed among these build- 
ings were the low, flimsily built shops, dwellings 
and offices of typical Japanese wood design and 
construction. The street pattern was an irregular 
block plan with variations imposed by the flow 
of inter-island traffic and the irregular shapes of 
the islands. 
9 b. Use. The central area of 6,000-foot radius 
accommodated, without more than rough func- 
tional separation, the principal commercial section 
of the city and large parts of the residential and 
military sections, but there were no industries of 
appreciable size nearer than 8,900 feet to the city 
center. The industries were located mainly on 
the eastern perimeter of the city or on the southern 
('lids of the islands. Seventy-five percent of the 
245.000 inhabitants at the time of the attack were 
in the congested 4-squarc mile city center, giving a 
density of population in this area of approximately 
46.000 persons per square mile. The overcrowd- 
ing and population density were largely attrib- 
utable to the geographical limitations imposed by 
the islands and to the 42 percent of utilizable land 
area within the city monopolized by the military 
who, in addition, used 80 percent of the facilities 
of Ujina Harbor (sec. IV, par. 15). 
c. Climate. Having hot, humid summers and 
mild winters, with a mean annual temperature of 
57.9° F. (about the same as that of Baltimore, 
Md.), the climate was characterized by a rainy 
season from the latter part of April through June 
and all of September. Light, warm, southerly 
winds blew from May through October, and 
northerlies and westerlies the remainder of the 
year. The typhoon season lasted from June 
through October with winds varying up to 75 
miles per hour accompanied by torrential rains. 
Between the dates of the atomic-bomb attack on 
6 August 1945 and the arrival of the team on 
14 October 1945, two severe storms occurred, of 
which at least one had an intensity such as would 
be encountered only once in perhaps 50 or 100 
years. These storms, unfortunately, destroyed 
much evidence of physical damage (especially to 
bridges) as well as public records and other data 
which had remained after the attack. 
d. High-Explosive Attacks. Prior to the atomic- 
bomb attack the only aerial actions reported by 
the Japanese against Hiroshima proper were (1) 
an attack on 19 March 1945 by 4 or 5 Navy planes 
and (2) an attack on 30 April 1945 by a lone B-29. 
The Navy planes dropped two 250-pound bombs 
and the B-29 dropped ten 500-pound bombs, or a 
total of 5,500 pounds for both attacks. (A total 
of seven high-explosive attacks was reported by 
the Office of Statistical Control, Headquarters, 
AAF, totaling 58 tons of high explosives and 
incendiaries.) Since the areas affected by these 
attacks later suffered severely from the atomic 
bomb it was impossible to evaluate precisely the 
effective damage. The following data, therefore, 
are offered only as a recapitulation of damage 
figures obtained from interrogation of residents 
and city officials. 
Casualties 
Attack of— 
Killed 
Wounded 
Total 
19 March 1945___ 
2 
None reported 
2 
30 April 1945_ 
10 15 
25-30 
35-45 
Damage to buildings 
Attack of— 
Destroyed 
Minor damage 
Total 
19 March 1945_._ 
2 
None reported 
2 
30 April 1945^_ 
22 
2 
24 
Of the 26 buildings damaged, 22 were typical 
Japanese domestic structures, 3 were wood-frame, 
and one was of load-bearing, brick-wall construc- 
tion. The ‘only fire reported was from a direct 
hit on a warehouse by a 500-pound bomb. The 
fire burned for two hours, destroying some electric- 
wire cable, transformer oil, paint, and a small 
amount of gasoline. 
D. THE ATOMIC-BOMB ATTACK 
1. Sources of Information 
No details of the attack preparations, approach 
to the target, release of the bomb, elements of the 
explosive or method of detonation of the atomic 
bomb dropped on Hiroshima have been made 
available for this report. Therefore, the following 
is an account of the attack as experienced and 
described by the Japanese themselves. The data 
were obtained through interrogation and from 
Japanese reports prepared by the Kure Naval 
District and the governor of Hiroshima Prefecture. 
a. Meteorogical Conditions. The morning of 6 
August 1945 was clear, with a few clouds at high 
altitude. Wind was from the south with a veloc- 
ity of about 4.5 miles per hour. Visibility was 10 
to 15 miles. 
b. Conditions in the City. An air-raid “alert” 
was sounded throughout Hiroshima Prefecture at 
0709 hours. Reports of the number of planes 
sighted were conflicting. The aircraft circled the 
city and withdrew at 0725 hours. The “all-clear” 
signal was sounded at 0731 hours. 
c. The Attack. The aircraft committed in the 
10 atomic-bomb attack were first sighted at 0806 
hours when Matsunaga lookout station reported 
two enemy aircraft proceeding northwest. This 
figure was corrected to three aircraft at 0809 
hours. The sound of aircraft engines was picked 
up by the Nakano searchlight battery at 0814 
hours. Enemy aircraft were reported heading 
southwest over Saijo, 15 miles east of Hiroshima 
at 0815 hours. (No air-raid signal was sounded 
after the “all-clear” at 0731 hours probably be- 
cause the authorities and residents were accus- 
tomed to formations of enemy planes passing over 
the city.) Three aircraft arrived over Hiroshima 
at an altitude of 23,000 feet, with the lead plane 
700 to 1,000 feet ahead of two others which were 
following abreast. The lead plane changed course 
to the northwest after dropping the bomb. The 
two following planes released parachutes and 
changed course to the south. At this moment, 
within a minute before or after 0817, the atomic 
bomb detonated. 
d. Post-Attack. After the attack, the lead plane 
headed east or northeast. The other two planes 
were unreported other than the sighting of one 
light aircraft proceeding south at low altitude. 
E. ZERO POINTS 
1. Definition 
The zero point may be defined as the point of 
detonation of a bomb. When a bomb detonates 
in the air the point has location in both plan and 
elevation. The atomic bomb at Hiroshima burst 
in the air. Throughout this report the ground 
location of the point directly under the point of 
its air burst is designated as ground zero, abbre- 
viated GZ, and the actual point of detonation in 
the air is designated air zero, abbreviated AZ. 
The locations of GZ and AZ were developed from 
flash-marks found on surfaces readily scorched or 
spalled by radiant heat from the explosion. 
Edges of unscorched surfaces, or “shadows” on 
otherwise burned surfaces, that were shielded by 
some object in the path of the heat waves afforded 
directions and elevations for the location of the 
point of detonation. 
a. Location and Elevation. Employing the 
World Polyconic Grid system of mapping (based 
on 1,000-yard grids) GZ was located at coordinates 
744,200-1,261,850 yards, approximately 700 feet 
southeast of the east end of Bridge 24, and AZ 
was found to be slightly above 2,000 feet. The 
calculations of British and Japanese teams closely 
approximated the findings of this team. 
F. JAPANESE BUILDINGS 
1. Masonry and Steel Buildings 
From the opening of Japan to trade in 1853, 
when Commodore Perry sailed his well-armed 
ships of the United States Navy into Uraga Har- 
bor, until the great Tokyo earthquake of 1923, the 
design and construction of civic, commercial, and 
industrial buildings, except those of wood frame, 
were directed largely by architects and engineers 
trained in, or imported from, America and Europe. 
During this period little attention was paid to 
earthquake-resistant design and the majority of 
the buildings erected were load-bearing brick-wall 
or relatively light steel- or concrete-frame con- 
struction, generally similar to occidental buildings. 
The great disaster of 1923, however, caused such 
severe damage to all types of structures that 
radical revisions were instituted in construction 
practices. A national building code based on 
aseismic design was adopted on 1 July 1924, which 
required greatly increased strength in all struc- 
tural framing systems, making them about 50 to 
70 percent stronger and 50 percent heavier than 
usual occidental designs, and, at the same time, 
through restrictive clauses, discouraged many 
existing practices in the building industry by 
making the use of brick, hollow tile, concrete block, 
and wood economically impracticable except for 
dwellings and small shops. Because, however, of 
the economic depression of 1930 and the later need 
for ferrous metals in the military program, the 
new code was not enforced. Therefore, except in 
large cities and industrial centers, the buildings 
erected in compliance with the code constituted a 
small fraction of the total number. Some of the 
important provisions of the new code were: 
a. Resistance. All buildings other than domestic 
structures were designed to resist a lateral force 
equal to 0.1 the total weight of the completed 
structure distributed according to the weight of the 
building. 
h. Wood-frame buildings were limited to 30 feet 
at eaves or 42 feet over-all. Column sizes (areas) 
were increased about 20 percent over previous 
requirements and knee braces and other lateral 
braces were made mandatory. 
c. Brick structures were limited to 30 feet at 
eaves and 42 feet over-all and the maximum length 
of unsupported wall was set at 30 feet. Walls 
were required to have a minimum thickness of 
one-fifteenth the story height or for exterior walls 
11 one-tenth the wall height, whichever was the larger, 
except that minimum thicknesses of 1 foot for 
walls less than 18 feet long and 1 foot 4 inches 
for walls 18 feet to 30 feet long were specified. 
d. Steel-frame buildings were limited to 100 feet 
in height. Joints between columns and girders 
had to be made rigid (capable of resisting moment) 
and heavy brackets or knee braces had to be used. 
Diagonal bracing or reinforced-concrete walls 
rigidly connected to the framing and capable of 
resisting the lateral aseismic loadings were re- 
quired. Curtain walls had to be rigidly fixed to 
the structural frame. Hollow tile could not be 
used for exterior walls. 
e. Reinforced-concrete-frame buildings were lim- 
ited to 100 feet in height and continuity was re- 
quired in design. Columns were limited to a 
length to the least dimension ratio of 15 to 1 with 
1.25 percent reinforcement, and main beams or 
girders were required to have double reinforce- 
ment and stirrups for their full length. Reinforced- 
concrete walls and partitions were designed to 
resist the lateral forces, and curtain walls were 
subject to the same restrictions as for steel-frame 
construction. 
/. Combined stresses for ordinary plus earth- 
quake loadings were required not to exceed ordi- 
nary allowable stresses. 
2. Wooden Buildings 
Despite the encouragement of Western con- 
struction practices and the official adoption of 
aseismic design for large buildings, wood-frame 
and wood-polo buildings remained of a design and 
construction indigenous to Japan and unfamiliar 
to most Occidentals. The great majority of the 
wood-frame buildings were dwellings, combination 
shop-dwellings, small commercial and industrial 
buildings, and military barracks. Together, the 
dwellings and shop-dwellings comprised the bulk 
of any Japanese urban target and enhanced to a 
high degree its vulnerability to fire and blast 
weapons. 
a. The Traditional City. Residential areas in 
Hiroshima, like those in other Japanese cities, 
were characterized by a high degree of built- 
upness resulting from a density of population 
comparable to some of the worst slum districts 
in large American cities. One- and two-story 
wood-frame buildings roofed with tile were built 
almost solidly along the streets, with numerous 
outhouses, wood garden walls, and fences to their 
rear, which occupied most of the remaining ground 
area within the block. Streets were very narrow 
and laid out in a rectilinear pattern except where 
topographical features interfered. Sidewalks were 
seldom found, the street being used for pedestrian 
as well as vehicular traffic. Open gutters on the 
sides of the streets carried away drainage and 
waste water from the houses. In areas where the 
residential section was not clearly defined, small 
combination shop-dwellings opened directly onto 
the street with the owners living to the rear or on 
the second floor. These buildings, however, did 
not differ in details of construction from the usual 
dwellings. 
h. Wood-Frame Construction was usually the 
work of local carpenters who, as a rule, were 
highly skilled in intricate and delicate joinery and 
finishing but lacked any knowledge of elementary 
statics. The practices followed made their 
wooden construction fall far below American 
standards of strength, rigidity, and weather- 
tightness. Apparently, sizes of the fame members 
were determined by general practice and the 
materials available rather than by either calcula- 
tion or guess of loads and stresses, and members 
used under the same conditions might vary greatly 
in size. A minimum of rough hardware or nails 
was used, the members being joined by wood 
pegs, mortise and tenon and other joints cut on 
the job. The weak joints tended to make the 
members larger than would be used in American 
construction of a similar type, especially in trusses 
where the joints failed to develop the strength 
of the heavy members. In contrast, columns were 
invariably too slender, their buckling being the 
most common type of failure in wooden buildings. 
Other notably poor design details were (1) beams 
dapped to half their total depth, (2) trusses and 
beams framed into girders and over wall openings, 
(3) weak wall plates and lack of column caps or 
bolsters, (4) lateral knee bracing cut into the 
slender columns and good only in compression, 
and (5) heavy burnt-tile roofs set in mud and 
straw on thin boards. The better wood-frame 
construction used dimension lumber while the 
poorer construction, which was more common, 
utilized wood poles and sometimes half polos. 
Construction lumber was generally pine or fir. 
c. Wood-Pole Construction, although employing 
truss forms, was weak structurally and was not 
comparable with any type of United States con- 
struction. Roofs of tile bedded in mud on wood 
sheathing and walls of mud plaster (Dozo) over 
12 bamboo lath were common for this type of con- 
struction. 
3. Blast Vulnerability of Wood Construction 
Resistance to blast is roughly inversely pro- 
portional to mass and strength. The typical 
Japanese wood buildings were generally light- 
frame structures with relatively heavy roofs 
supported by slender columns. Lateral rigidity 
was normally provided by moments developed by 
mortise-and-tenon joints between columns and 
roof beams. The panel walls of mud plaster on 
bamboo lath were only lightly fastened to the 
frame and frequently were stripped without 
rupturing the frame. The light weight, slender 
columns and poorly designed joints were points 
of weakness which rendered the buildings highly 
vulnerable to damage by blast. Failure commonly 
resulted either from buckling of external columns 
by blast or by a mass distortion of the structure 
away from the direction of blast. Because 
Japanese residential areas were densely built up 
with dwellings and shop-dwellings, walls were 
usually shielded from blast by adjacent buildings. 
Consequently, failure by mass distortion was 
probably the most characteristic damage effect 
since this could readily result from blast impinging 
on the roofs of buildings. 
4. Fire Vulnerability of Japanese Dwellings 
General opinion in the United States has been 
that Japanese dwellings are “tinder boxes.” 
Considering the dwellings collectively in their 
natural surroundings in a congested city, this 
opinion is well founded; but considering an 
individual dwelling set off by itself, the appraisal is 
inaccurate. Collectively, Japanese dwellings are 
extremely vulnerable to fire because of the high 
degree of congestion of residential areas; light, 
exterior, wood sheathing; broad, open, wood 
eaves; and air spaces under the first floors. All 
these features tend to assist fire spread. On the 
other hand, the heavy tile roofs practically 
preclude their ignition by flying embers and 
thatched roofs are usually found only outside 
city limits. 
a. Fire Frequency. Actually, frequency of fires 
in individual Japanese dwellings is less than one- 
half that in American houses. This condition can 
be attributed to the fact that the Japanese dwell- 
ing is generally less susceptible to ignition because 
of the lesser amount of combustible furnishings 
and the higher moisture content of wood and 
furnishings. In addition, there are fewer internal 
sources of ignition and more careful supervision 
by the occupants. Once a fire progresses beyond 
the state of incipiency, however, a Japanese dwell- 
ing burns rapidly. 
G. CAUSE AND EXTENT OF FIRE 
1. Conditions Prior to Attack 
The city of Hiroshima was an excellent target 
for the atomic bomb from a lire standpoint: There 
had been no rain for three weeks; the city was 
highly combustible, consisting principally of Japa- 
nese domestic-type structures; it was constructed 
over flat terrain; and 13 square miles (including 
streets) of the 26.5-square-mile city was more 
than 5 percent built up (i. e., covered by plan 
areas of buildings). The remainder of the city 
comprised water areas, parks and areas built up 
below 5 percent. Sixty-eight percent of the 13- 
square-mile area was 27 to 42 percent built up 
and the 4-square-mile city center was particularly 
dense, 93.6 percent of it being 27 to 42 percent 
built up. 
a. Fire Department. Public fire equipment had 
been little improved in anticipation of wartime 
fires. Private fire equipment had been aug- 
mented somewhat but instruction to home occu- 
pants in its use had been limited to training in 
combating incendiary bombs. 
h. Water Supply. The public water system 
was fairly adequate for normal fire conditions, 
although pressure was very low on dead-end 
mains at the south end of the city. No improve- 
ments except the addition of some static tanks 
had been made for wartime emergencies. 
c. Firebreaks. Firebreaks totaling 41,000 feet 
had been prepared by removing combustible build- 
ings on one or both sides of fairly wide streets. In 
addition, the Ota River and its branches which 
divided the city into nine distinct areas were effec- 
tive natural firebreaks. Complete or part fire- 
break clearance had been effected around 22 of the 
buildings studied. 
2. Ignition of the City 
The temperature resulting from the explosion of 
the atomic bomb was of great intensity but of 
extremely short duration. At ground zero, 2,000 
feet from the center of heat, the temperature prob- 
ably exceeded 3,500° C. for a fraction of a second. 
Only directly exposed surfaces were flash burned. 
Measured from GZ, flash-burns on wood poles were 
observed at 13,000 feet, granite was roughened or 
spalled by heat at 1,300 feet, and vitreous tiles on 
13 roofs were blistered at 4,000 feet. 
a. Evidence relative to ignition of combustible 
structures and materials by heat directly radiated 
by the atomic bomb and by other ignition sources 
developed the following: (1) The primary fire haz- 
ard was present in combustible materials and in 
fire-resistive buildings with unshielded wall open- 
ings; (2) six persons who had been in reinforced- 
concrete buildings within 3,200 feet of air zero 
stated that black cotton black-out curtains were 
ignited by radiant heat; (3) a few persons stated 
that thin rice paper, cedarbark roofs, thatched 
roofs, and tops of wooden poles were afire immedi- 
ately after the explosion; (4) dark clothing was 
scorched, and, in some cases, reported to have 
burst into flame from flash heat; (5) but a large 
proportion of over 1,000 persons questioned was in 
agreement that a great majority of the original 
fires was started by debris falling on kitchen char- 
coal fires, by industrial process fires, or by electric 
short circuits. 
b. Hundreds of fires were reported to have 
started in the center of the city within ten minutes 
after the explosion. Of the total number of 
buildings investigated 107 caught fire, and, in 69 
instances, the probable cause of initial ignition of 
the buildings or their contents was established as 
follows: (1) 8 by direct radiated heat from the 
bomb (primary fire), (2) 8 by secondary sources 
and (3) 53 by fire spread from exposing buildings. 
3. The Conflagration 
During the first half-hour after the attack, 
individual fires spread in all directions; there- 
after, spread, at least at the perimeter, was prin- 
cipally toward the city. Although the velocity 
of the wind on the morning of the atomic-bomb 
attack was not more than 5 miles per hour, a 
fire storm, including both wind and rain, began 
to develop soon after the start of the initial fires. 
The fire wind, which blew continuously toward the 
burning area, reached a maximum velocity of 30 
to 40 miles per hour 2 to 3 hours after the explo- 
sion, and intermittently light and heavy rain fell 
over the north and west portions of the city. As 
the fire wind increased in intensity, fires in the 
city were merging, but practically all fire spread 
beyond 6,000 feet from GZ had ceased 2 hours 
after the attack. A large portion of the burned- 
over area resulted from the spreading and merging 
of the original fires. Beyond 5,000 feet from GZ 
built-upncss influenced the extent of fire spread. 
a. Fire Department. The public fire depart- 
merit sustained an instantaneous, paralyzing 
blow from which it could not recover. Eighty 
percent of the firemen on duty were killed or crit- 
ically injured, 60 percent of the public fire stations 
were totally damaged and 68 percent of the public 
fire-pump trucks were destroyed. However, no 
modern well-equipped public fire department could 
have prevented the conflagration from developing 
in the city. 
b. Water supply. One major break occurred in 
a 16-inch water main when Bridge 29 was collapsed 
by blast. This and a large number of breaks in 
small pipes above ground in collapsed buildings 
reduced water pressure in the system; however, 
the reservoir did not run dry and lack of water was 
not a factor in the extent of the fire. 
c. Fire spread. There were relatively few 
buildings to which fire definitely failed to spread. 
The blast of the bomb had rendered practically all 
wall openings unprotected, or in the case of non- 
combustible and combustible buildings, had col- 
lapsed walls and roofs, or stripped wall and roof 
sheathing. Thus, conditions were ideal for spread 
of fire from exposing buildings. The average 
distance between buildings to which fire may have 
spread and the nearest burned building was 20 
feet, compared with 50 feet to buildings to which 
fire definitely did not spread. The probability of 
fire spread increased rapidly but in a decelerating 
trend as built-upness increased in the lower ranges 
above 12 percent, and decreased rapidly but in a 
decelerating trend as exposure distances increased 
in the lower ranges up to 50 feet. There appeared 
to be practically a straight line relationship be- 
tween probability of fire spread and built-upness 
above 40 percent, and an inverse straight-line 
relationship between fire spread and exposure 
distances above 50 feet. 
d. Fires within buildings. Once ignited, fires 
spread inside most of the buildings since prac- 
tically all had either unprotected interior walls 
and floor openings or ruptured interior walls and 
floors after the bomb blast, and most contents 
were combustible. 
4. Extinguishment of Fire 
Except in a few reinforced-concrete buildings, 
almost no effort was made to fight the conflagra- 
tion except at the outer perimeter which finally 
encompassed 4.4 square miles. Most of the fire 
had burned itself out or had been extinguished on 
the fringe by early evening on the day of the 
attack. Smoldering persisted in the burned-over 
14 area for three or four days. A combination of the 
fire wind, fire fighting, streets and low built-upness 
stopped the fire at the perimeter. The public fire 
department played a minor role in the extinguish- 
ment of the conflagration. Hand fire equipment 
used in extinguishing incipient fires in a few fire- 
resistive buildings within the burned-over area and 
in saving many dwellings on the fire fringe proved 
to be the most effective fire-fighting equipment. 
At the fire perimeter, exposure distance had a 
direct bearing on the extent of fire spread. Fire 
fighting was a factor in stopping spread of fire in 
only four of 58 fire-resistive buildings which were 
fire damaged. 
a. Value of firebreaks. Although firebreaks, 
both natural and man-made, were generally in- 
effective, their value cannot be discounted en- 
tirely. Firebreaks assisted in preventing the 
burn-out of seven fire-resistive buildings and one 
noncombustible building. If the bombing had 
been less accurate at Hiroshima, or if a single bomb 
had been dropped on a city of greater area, fire- 
breaks might have limited spread of fire. 
5. Fire Damage 
a. Buildings and Contents. Of the total floor 
area in the 130 buildings studied, 72 percent of 
fire-resistive buildings, 59 percent of noncom- 
bustible buildings, and 80 percent of combustible 
buildings were burned subsequent to blast and 
debris damage; 58 of 64 fire-resistive buildings, 8 
of 12 noncombustible buildings, and 41 of 54 com- 
bustible buildings within or adjacent to the 
burned-over area had fire damage. However, fire 
damage in 4 of the fire-resistive buildings and 1 
of the combustible buildings was negligible. Only 
3 fire-resistive buildings sustained structural 
damage by fire. Damage by fire to the interior 
and contents of fire-resistive buildings greatly ex- 
ceeded damage by blast and debris. Most of the 
fire-resistive buildings had combustible interior 
finish as well as a considerable amount of com- 
bustible contents, and combustion in the portion 
of the buildings which burned was practically 
complete. Noncombustible and combustible 
buildings were structurally damaged principally 
by blast, but fire caused the major part of severe 
damage to contents. About one-half of the non- 
combustible buildings and most of the combustible 
ones had combustible contents. 
h. Bridges. Of the 8 bridges damaged by fire 
all were wood and all were ignited by spread of fire 
from nearby combustible buildings. The average 
distance from the ends of the 8 bridges which 
caught fire to the nearest burned buildings was 
35 feet, as compared to 70 feet for the 7 com- 
bustible bridges which did not catch fire. 
c. Extent of Fire Damage. The blast study 
determined that the extent of complete structural 
damage to dwellings in Hiroshima had a mean 
radius of 7,300 feet measured from GZ, whereas 
the fire study determined that the extent of com- 
plete destruction of combustible buildings by fire 
had a mean radius of 6,250 feet. Totally damaged 
buildings within the 7,300-foot radius numbered 
approximately 59,000 and within the 6,250-foot 
radius, 50,000. Fewer buildings beyond 5,000 
feet collapsed completely, so that secondary fires 
occurred infrequently except in densely or mod- 
erately built-up areas. The extent of fire was 
influenced principally by the location of the bomb 
burst, the shape of the densely or moderately 
built-up central part of the city, and the fire wind. 
d. Protective Measures. Precautionary fire 
measures were ineffective largely because of wide- 
spread blast damage, the high casualty rate, 
innumerable fires started throughout the city on 
both sides of the natural and man-made firebreaks, 
and the knock-out blow to the fire department. 
Standpipes and hose in fire-resistive buildings were 
not used because of casualties to personnel. 
There were no automatic sprinkler systems in 
Hiroshima buildings. (It is believed that they 
could have been of value in buildings strong 
enough to resist the blast, provided there was an 
adequate and continuous water supply.) There 
were no open sprinkler systems for protection of 
wall openings. (Externally installed systems on 
reinforced-concrete buildings generally would have 
remained intact except where directly exposed to 
the blast.) Steel-roller shutters at exterior wall 
openings showed a definite inability to withstand 
the blast pressures. They were completely blown 
in at 5,200 feet from air zero, whereas steel- 
hinged shutters on openings of approximately the 
same size and shape at the same distance were 
only slightly bent. The steel-roller shutters, 
however, showed advantages over sliding fire doors 
at interior wall openings. Reinforced-concrete 
fire walls in buildings, even in wood- and steel- 
frame structures with light sheathing, withstood 
blast pressures, whereas brick fire walls at the 
same or greater distances from zero were seriously 
cracked or partly or completely collapsed. 
15 H. DAMAGE TO BUILDINGS 
I. Scope of Investigation 
The 173 buildings in this study included vir- 
tually every reinforced-concrete, every steel-frame 
and every load-bearing, brick-wall building from 
GZ to a distance beyond which there was no 
further effective damage. Selected among build- 
ings constructed of dimension timbers, sufficient 
wood-frame structures to give a usable sample 
of construction details and extent and character 
of damage at varying distances from GZ were 
studied in detail. In addition, most of the struc- 
tures of wood-pole construction were located and 
the approximate extent of structural damage to 
each was estimated. The mean line of structural 
damage to residential-typo structures was estab- 
lished by field examination and the limits of roof 
stripping were established and plotted. A sum- 
mary for each type of construction follows: 
a. Because of aseismic design, multistory con- 
struction in Hiroshima generally was 50 percent 
heavier and 50 to 70 percent stronger than in 
comparable United States practice. However, a 
small number of buildings of substandard design 
or construction was found. Concrete was quite 
variable in quality, some being very poor and 
the best being about comparable with good 
United States quality. 
b. Light, steel-frame buildings were of excellent 
workmanship and materials but were slightly 
lighter than those in United States used for similar 
occupancies. 
c. Load-bearing, brick-wall construction was 
excellent and compared favorably with better 
United States and European construction, being 
if anything, somewhat heavier and stronger than 
United States construction for similar occupancies. 
d. Wood-frame construction, although employ- 
ing heavier trusses, was weaker than usually 
found in the United States for similar occupancies 
because of poor details. Present in Hiroshima 
was a large number of buildings of weak, wood- 
pole construction. 
2. Cause and Extent of Damage 
The primary cause of damage to buildings in 
Hiroshima was blast, similar to that caused by 
heavy charges of high explosive but on a much 
larger scale. The damage from this unprecedent- 
edly powerful and effective blast weapon was 
characterized by distortion or crushing of entire 
buildings rather than collapse or fracture of a 
single member. In many cases, especially in 
steel-frame buildings, distortion was increased by 
the subsequent fires. Structural blast damage to 
dwellings and other wood-frame buildings extended 
to 7,300 feet from ground zero, which was 1,050 
feet beyond the fringe of fire damage. On all 
types of buildings, wall and roof stripping extended 
to 22,000 feet from GZ while glass breakage was 
reported beyond 37,000 feet. Comparison of the 
atomic bomb with high-explosive weapons results 
at best in a very rough approximation because of 
the necessary assumptions. Based upon damage 
to load-bearing, brick walls an equivalent bare 
charge of TNT of approximately 4,400 tons was 
estimated. 
a. Mean Areas of Effectiveness (MAE) are based 
on unsatisfactorily small samples of each class of 
building studied, except dwellings. Therefore, 
they shoyild be considered merely as indicating the 
order of magnitude of damage. The MAE’s, 
especially those computed by the annular ring 
method (used for all MAE’s except residential 
construction for which the average circle method 
was employed), are greatly influenced by the height 
of AZ, and relate only to one particular bomb det- 
onating at one particular height. The mean 
areas of effectiveness of the atomic bomb for 
structural damage about ground zero and the 
radii of the MAE’s for the various classes of build- 
ings present were computed to be as follows: 
Building classifications 
MAE’s in 
sq. mi. 
Radii in ft. 
Multistory, earthquake-resistant- _ 
Multistory, steel- and reinforced-con- 
crete-frame (including both earth- 
quake- and non-barthquake-resist- 
0. 03 
500 
ant buildings) 
. 05 
700 
One-story, light steel-frame 
3. 4 
5, 500 
Multistory, load-bearing brick-wall 
3. 6 
5, 700 
One-story, load-bearing brick-wall 
Wood-frame, industrial-commercial 
6. 0 
7, 300 
(dimension-timber construction) 
Wood-frame, domestic buildings 
8. 5 
8, 700 
(wood-pole construction) 
9. 5 
9, 200 
Residential construction 
6. 0 
7, 300 
Values for wood-frame and residential construc- 
tion are peculiar to Japan and are not applicable 
to any other locality. 
b. Contents damage resulted principally from 
fire, and, except for multistory, steel - and concrete- 
frame buildings, contents and structural damage 
to buildings was generally of similar extent at 
corresponding distances from GZ. In multistory, 
16 frame construction, fire caused the major portion 
of all damage to contents, there being 25 to 40 
percent initial damage from blast and debris. 
Contents in light, steel-frame buildings suffered 
moderate initial damage from blast, but when 
located in the 4.4-square-mile, burned-over area 
were practically consumed by fire. Outside the 
burned-over area there was some exposure damage. 
In load-bearing, brick-wall buildings within 2,000 
feet of GZ, blast and debris were the major cause 
of damage to contents, additional damage result- 
ing also from fire and exposure. Beyond 2,000 
feet from GZ, fire was the major cause. Within 
the burned-over area practically all contents of 
wood-frame buildings were consumed by fire with 
slight to moderate damage from blast, debris, and 
exposure beyond the fire fringe or burned-over 
area of 4.4 square miles. 
3. Characteristics of Damage 
Blast damage to buildings spread uniformly in 
all directions, residting in an approximately 
circular area of devastation. Limiting distances 
to which buildings were damaged depended upon 
their strength and construction. Thus, the heavy, 
strong, multistory, steel- and concrete-frame 
structures were damaged only in an area relatively 
near the point of detonation and their burned-out, 
but otherwise undamaged, structural frames rose 
impressively from the ashes of the burned-over 
section where occasional piles of rubble or twisted 
steel skeletons marked the location of brick or 
steel-frame structures. At greater distances steel 
and brick structures remained undamaged. Blast 
damage to wood-frame buildings and residential 
construction beyond the burned-over area grad- 
ually became more erratic and spotty as distances 
were reached at which only the weakest buildings 
were damaged. In the outer sections of the city 
there were locations where there was no damage 
other than breakage of glass or minor disturbances 
of tile roofs. 
a. Effects of Pressures. Experiments with high 
explosives have shown that face-on peak pressures 
are approximately two to five times as large as 
side-on peak pressures and consequently greater 
damage results to walls and roofs facing the blast 
than to similar surfaces parallel with the blast. 
These directional characteristics were very appar- 
ent at Hiroshima. Thus, near GZ where the blast 
was almost vertically downwards, buildings were 
crushed or roofs were crushed with little or no 
damage to the walls. At somewhat greater dis- 
tances both horizontal and vertical components 
of the blast were appreciable and buildings suffered 
damage both to roofs and to walls facing the blast. 
At considerable distances from the bomb the blast 
was traveling in an almost horizontal direction 
and damage was predominantly to walls facing 
the blast. Data were not sufficient to determine 
whether Mach Reflection of the blast wave 
occurred. 
b. Characteristics of Blast Pressures. Blast 
pressures of high explosives rise almost instantan- 
eously, decay more slowly, and then fall below 
atmospheric pressure for a period of time usually 
about three times as long as the period during 
which they were above atmospheric pressure. 
The above atmospheric pressure period is termed 
the positive phase of the blast and the period 
below atmospheric pressure, the negative phase. 
Pressure during the negative phase while much 
lower than that of the positive phase nevertheless 
residts in charcteristic damage such as glass or 
window shutters blowing out toward the blast. 
Damage typical of the negative phase was rela- 
tively uncommon. The few failures (such as 
plaster stripping) which could be attributed to the 
negative phase were in places where the resistance 
to the positive phase was much greater than to 
the negative. 
c. Shielding. Shielding, or protection from 
blast by intervening objects, was observed in a 
few cases. One load-bearing, brick-wall structure 
was protected from blast by an adjoining building 
and suffered less wall damage than the average 
at its distance from GZ. In the eastern part of 
the city a number of houses which should have 
been damaged survived because of protection by 
an intervening hill. Near GZ there was little or 
no shielding since the buildings were so low com- 
pared with the height of AZ that they could not 
effectively shield one another. 
d. Reflection and Diffraction. Both reflection 
and diffraction phenomena of the blast wave were 
observed in Hiroshima. Diffraction was evi- 
denced by damage in locations where shielding 
should have afforded protection, had the blast 
wave travelled entirely in straight lines. The 
most frequent evidence of reflection was the 
destruction of parapet walls on the side away from 
the bomb while the parapet wall facing the bomb 
was undamaged, the most probable explanation 
being that the blast wave reflected from the roof 
surface reinforced the blast impinging directly 
upon the wall and resulted in its destruction. e. Suppositions. Had the point of detonation 
been lowered, for example to between 500 and 
1,000 feet above the ground, it is believed that 
damage to multistory, steel- and reinforced-con- 
crete-frame buildings close to GZ would have been 
markedly increased. The extent of damage which 
would have resulted had the bomb penetrated into 
the eaith is unknown and cannot be approximated 
until data are available on earth shock and crater- 
ing action of the atomic bomb. 
I. DAMAGE TO MACHINE TOOLS 
1. General 
The major industrial plants of Hiroshima were 
located about 1){ miles from the heart of the city 
and no damage was done to machine tools in them. 
Numerous small engineering shops, principally 
light ones containing 2 to 40 machine tools, were 
located within the central area. Machine tools in 
19 one-story buildings (11 wood-frame, 5 steel- 
frame, and 3 load-bearing, brick-wall structures) 
all of which were combustible except one which was 
noncombustible, were included in this study. 
There were no reinforced-concrete machine shops. 
Four of the 19 buildings were outside the burned- 
over area but were within 7,600 feet of ground zero. 
Fifteen of the buildings sustained practically 100 
percent structural damage. The vulnerability of 
all buildings to high explosives was V4 (Reference 
tables). 
a. Extent oj Damage. All machine tools within 
3,500 of GZ were seriously damaged, principally 
by fire. Throughout the 4.4-square-mile, burned- 
over area, except in four unburned shops, all 
machine tools were seriously damaged by fire after 
sustaining less than 15 percent serious damage by 
debris. Serious damage to machine tools in excess 
of 15 percent was caused by debris in only one 
shop. Weather was the only cause of damage to 
machine tools outside the burned-over area. The 
MAE for serious damage to machine tools by fire 
in combustible buildings was virtually the 4.4- 
square-mile, burned-over area of the city, but the 
number of machine tools in various types of 
buildings in the blast-affected area was much too 
small to permit calculation of reliable MAE’s for 
serious damage by blast and debris. 
2. Machine Tool vs. Building Damage 
a. In Wood-Frame Buildings. Debris caused 
serious damage (total or heavy) to only 3 percent 
of the machine tools in wood-frame buildings 
although 64 percent of the total floor area was 
structurally damaged by blast. Fire was the 
principal cause of serious damage to machine tools 
in this type of building. Seven of the 11 buildings 
vere burned and all their machine tools were 
seriously damaged. Serious damage by fire resulted 
because of the combustibility of the buildings and 
their contents, and the congested area in which 
they were located. A few machines were slightly 
damaged when overturned by mass movement of 
the building frames. 
h. In Steel-Frame Buildings. Debris caused no 
serious damage to machine tools in steel-frame 
buildings although 42 percent of the total plan 
area was structurally damaged by blast, because 
the blast rendered mass distortion of the steel 
frames without tearing loose heavy structural 
members and wall- and roof-sheathing debris was 
light. Fire was the cause of serious damage to 
machine tools in the steel-frame buildings. About 
30 percent of the total floor area of the steel-frame 
buildings was burned out and the same percentage 
of machine tools in them was seriously damaged 
by fire. 
c. In Load-hearing, Brick-wall Buildings. 
Debris caused serious damage to only 5 percent 
of the machine tools in load-bearing, brick-wall 
buildings although 30 percent of the total floor 
area was structurally damaged by blast. Fire 
caused serious damage to 23 percent of the ma- 
chine tools in this class of building. 
d. Weather Exposure. Exposure to weather 
caused slight damage to machine tools in buildings 
which were blast damaged but had no fire, and 
increased the degree of damage to machines which 
had already sustained heavy damage by fire. 
Rusting apparently was more severe on fire- 
damaged machine tools because all lubricants and 
paint had been burned off. 
J. DAMAGE TO BRIDGES 
1. Scope of Damage 
The atomic bomb caused relatively little struc- 
tural damage to Hiroshima’s 81 important bridges. 
Scattered over the entire city, 260 to 15,600 feet 
from GZ, they formed an adequate and efficient 
bridge system not only for local transportation 
needs but also as over-crossings for the city’s 
services and utilities, and as a connecting link on 
the important inland seacoast highway between 
Osaka and Shimonoseki. The most distant of the 
57 bridges studied was 12,200 feet from GZ, but 
18 no atomic-bomb damage was found beyond 7,600 
feet from GZ. Evidence of the ability of bridges 
to resist the forces of the atomic bomb (AZ at 
2,000 feet) was as follows: 10 of 19 timber bridges 
studied were undamaged; 10 of 15 concrete had 
no damage; and 14 of 23 steel were undamaged. 
Although great care was exercised in segregating 
the damage to bridges attributable to the atomic 
bomb from the flood and typhoon damage occur- 
ring on 17 September and 5 October, respectively, 
there is a distinct probability that the blast load- 
ings from the bomb weakened some of the bridges 
and left them in a more vulnerable state. Flood 
and typhoon w ere credited with damaging to some 
degree 9 timber, 7 concrete, and 3 steel bridges. 
2. Vulnerability 
Of the 3 types (timber, steel, concrete), timber 
bridges showed the least resistance to the atomic 
bomb. In terms of deck area, it was found that 
blast and fire from the atomic bomb destroyed 33 
percent of the 19 timber, 0 percent of the 15 con- 
crete, and 4 percent of the 23 steel bridges. These 
percentages do not include such damage as broken 
railings, curbs, copings and dislodged members, 
of which 5 concrete and 5 steel bridges showed a 
moderate amount. 
3. Mean Areas of Effectiveness 
There were insufficient data on bridges to com- 
pute reliable MAE’s for all types. The analysis 
of data, however, led to these conclusions on 
MAE’s for structural damage by blast: 
Square miles 
Timber bridges 2. 4 
Steel bridges 0 
Concrete bridges 0 
4. Damage in Relation to Use 
Effects on the city resulting from the atomic- 
bomb damage to bridges considered by class were 
as follows: 
a. Railroad Bridges. The six railroad bridges 
(5,580 to 8,480 feet from GZ), scattered around a 
horseshoe circle at the foot of the hills in the nor- 
therly part of the city, were as a class most dis- 
tant from GZ. Strongly constructed of steel, 
they completely escaped damage except for radiant 
heat effects which to a minor degree on five bridges 
discolored the paint on girders facing AZ. As an 
indirect effect, however, nearby fires resulting 
from the bomb, debris, and derailed freight cars 
on Bridge 9 disrupted railroad traffic for 2 days. 
b. Street Railway Bridges. The 9 street railway 
bridges (1,000 to 7,600 feet from GZ) were located 
generally in the heart of the city. Comprising 2 
timber, 1 reinforced-concrete, and 6 steel bridges, 
the damage incurred was limited to destruction by 
blast and fire of 1 timber bridge (4,670 feet from 
GZ) and blast damage to 2 steel bridges located 
1,000 feet and 4,670 feet from GZ, respectively. 
The 2 steel bridges were closed to traffic, 1 for 3 
and the other for 30 days. Although closing the 
latter isolated the Hiroshima railroad passenger 
station and northeast part of the city from street- 
car service for that period of time, the total of all 
damage to bridges carrying streetcar tracks was 
not serious. 
c. Highway Bridges. The 39 highway bridges 
comprising 14 timber, 15 concrete, and 10 steel 
bridges, were most numerous as a class. Scat- 
tered over the city, and varying in distance from 
the nearest (260 feet from GZ) to the most remote 
bridge (12,200 feet from GZ) included in this study, 
the effects of the bomb were varied. One steel 
bridge (1,190 feet from GZ) was totally collapsed 
by blast. Five steel bridges (260 to 7,600 feet 
from GZ) and five concrete bridges (4,270 to 6,450 
feet from GZ) were damaged in extent varying 
from distorted and displaced decks and minor 
structural members to broken railings, curbs, 
posts, and copings. Five timber bridges were 
structurally damaged by fire. Despite the six 
highway bridges totally damaged by the atomic 
bomb, the damage did not isolate any part of the 
city or seriously disrupt traffic except for debris 
on the approaches. 
d. Pedestrian Bridges. All four pedestrian 
bridges (3,200 to 7,960 feet, from GZ) were of 
timber construction. None was damaged by 
blast, but one (4,760 feet from GZ) was completely 
consumed by fire which spread from adjacent 
areas. The loss of this bridge wras no serious 
inconvenience since traffic was rerouted over a 
structurally undamaged bridge within a distance 
of 900 feet. 
e. Aqueducts and Overcrossings. Seven bridges 
(four timber and three steel) which served as 
aqueducts and overcrossings for utilities were 
structurally damaged by blast and fire. Of these, 
the four timber bridges and one steel bridge were 
totally collapsed. The collapse or failure of the 
seven bridges damaged 5,000 pairs of telephone 
wire in cables; one 16-inch and one 14-inch-diam- 
eter water main; 840 feet of 12-inch-diameter 
and 410 feet of 8-inch low-pressure gas mains; 
19 and 270 feet of 6-inch-diameter, high-pressure 
gas mains. To place these utilities in operation 
woidd have required complete rebuilding of five 
overcrossings and repairs to the other two. 
/. Other Factors Impeding Usefulness. When 
considering the usefulness of the bridge system 
immediately after the detonation of the bomb, 
factors which should be considered in addition to 
actual damage to the system were the innumerable 
fires in areas adjacent to bridge entrances and 
exits, the debris from collapsed buildings which 
cluttered the bridge decks and roadways and the 
general devastation and destruction, which, depriv- 
ing the city of the use of its bridges, temporarily 
trapped inhabitants on the islands without hope 
of immediate escape to, or relief from, the outside. 
Thirty hours elapsed before the first relief party 
penetrated the stricken area. Although the 
bridges generally resisted effectively the blast and 
fire from the bomb, lack of protection for the 
approaches and areas adjacent to the ends of the 
bridges rendered them almost useless at the time 
they wore most needed. 
5. Design, Construction, and Materials 
The bridges were designed in general to carry 
lower loadings than are provided in American 
practice. The design, details and arrangements 
also appeared to be below United States standards 
except for the steel-plate, girder, railroad bridges 
and steel-truss aqueducts which compared favor- 
ably with similar structures in the United States. 
In size, the steel used in bridges was comparable 
with United States standards. Insofar as could 
be determined by inspection, the quality of other 
materials was not equal to that used in similar 
structures in America. Samples of 2 cast-iron, 
railing-post sections were taken from Bridges 23 
and 24, and were forwarded to the Bureau of 
Standards, Washington, D. C., on 17 March 1946 
for tests. They were found “to correspond to 
ASTM Spec A48-41, class 20, the classification of 
lowest tensile strength for gray iron castings. 
However, the relationships among the tensile, 
compressive and shearing strength were about the 
same as in domestic cast irons of the class, and the 
carbon contents were perhaps somewhat higher, 
and the silicon and manganese contents consider- 
ably lower, than in most comparable cast irons.” 
6. Resistance of Bridges to Blast Loadings 
Since bridges are designed to resist predomi- 
nantly vertical loads, the fact that those near GZ 
received the blast forces largely in the direction 
of their greatest strength tended to minimize 
the damage to them. As evidenced by plate- 
girder Bridge 22, (260 feet from GZ and 2,020 
feet from AZ) the orientation of the longitudinal 
center line toward GZ also tended to decrease 
damage. The extended center line of Bridge 22 
passed within approximately 50 feet of GZ. 
Consequently, horizontal components of the 
blast were exerted in the direction in which the 
bridge was most resistant to such forces, while 
at the same time the probability of damage from 
reflected blast waves was minimized. Bridge 24 
(1,000 feet from GZ and 2,230 feet from AZ), 
with its extended center line passing approxi- 
mately 650 feet from GZ, was similar in strength 
and construction to Bridge 22. However, it was 
damaged more spectacularly and in a greater 
degree due to blast forces reflected from the water, 
and skewed broadside exposure to horizontal 
components of the pressure wave. Negative 
pressures were unimportant in causing structural 
damage, but posts and railings collapsed toward 
GZ indicated that, at the bridges within approxi- 
mately 1,000 feet of GZ, there was an inrushing of 
air following the initial positive blast. 
7. Suppositions 
It is probable that a bomb similar to the one 
used at Hiroshima, if detonated at an altitude 
lower than 2,000 feet, would cause appreciably 
more damage to bridges near GZ. But the height 
of detonation which would produce blast loadings 
exceeding the strength of the bridges is unknown. 
As discussed in the preceding paragraph, bridges 
near GZ have the advantage of receiving blast 
forces in the direction of their greatest strength, 
and when oriented toward GZ are most resistant 
to lateral forces as well as less liable to damage 
from reflected blast pressures. Therefore, the 
critical point of detonation for bridges would be 
one at which the blast loadings woidd be large 
enough to collapse the bridges by overloading the 
structural members. At lower altitudes of detona- 
tion it appears likely that the radius of damage at 
Hiroshima would have been decreased, due prin- 
cipally to the bridges being at ground elevation 
and therefore shielded to the maximum degree. 
Also, the damage probably would have been less 
regular in pattern owing to the irregularlity of 
natural and man-made topographical features. 
Whether or not the advantage of shielding would 
have been offset by the probably larger horizontal 
components of blast against the vertical exposures 
of the bridge members is speculative. 
20 K. DAMAGE TO SERVICES AND UTILITIES 
1. General 
The services and utilities of Hiroshima were the 
following: 
a. City railway and bus system. 
h. Government railroad system. 
c. Electric generating and distribution system. 
d. Telephone communications system. 
e. Water supply system. 
f. Sanitary and storm sewer system. 
g. Domestic gas system. 
All services and utilities were damaged to some 
extent and were disrupted in whole or part for 
varying lengths of time. Since the atomic bomb 
practically paralyzed the city, however, the de- 
mand for services fell off as sharply as the supply, 
and where services were needed they were restored 
to, or continued to operate at, minimum levels. 
To summarize: the railroads were operating 
through the city on 8 August, 2 days after the 
attack; some streetcar lines were open by 9 
August; the first telephone service was restored 
by 15 August; electric power was available to some 
parts of the city by 7 August; the water and 
domestic gas systems continued to serve outlying 
districts; and the sewer system, despite the loss of 
all pumping stations, functioned until the heavy 
rains of the middle of September raised the water 
level above the gravity flow lines of the open 
ditches, flumes, and underground mains. 
2. City Electric Railway and Bus System 
Hiroshima depended almost entirely upon 
streetcars and busses for passenger transportation 
within the city itself and to the outlying vicinities, 
including the resort town of Miyajima some 10 
miles to the southwest. In Hiroshima there were 
fewer than 25 private vehicles. The greatest 
recorded passenger traffic was for July 1945 when 
4,200,000 persons within the city and 800,000 
persons on the Miyajima branch used the cars and 
busses. The base of operations was the Senda- 
machi station consisting of 26 buildings, including 
the main offices, a converter station, warehouses 
and repair units. The other station, Yagurashita, 
was a single-building converter station situated in 
another part of the city, which divided the power 
output required to operate the system. Both 
stations received electrical power from the Chu- 
goku Electric Co., of Hiroshima at 22 kilovolts, 
alternating current, transforming and converting 
the alternating current to 600 volts, direct current, 
which was the operating voltage. 
а. Equipment. The transmission system was 
the overhead type supported by wood, steel, and 
concrete poles. It used a single copper conductor 
per pair of rails to supply electrical power to 
the cars. The entire 15.5 miles of the streetcar 
system within the city was double track, as was 
6 miles of the Miyajima section. The rails were 
of United States and Japanese manufacture having 
a gage of 4 feet 8.5 inches set on 8-inch ties, 
7 feet long. The company operated 123 cars 
(the largest weighing 18 tons empty and 26 tons 
loaded) rated at 37.3 kilowatts, and 85 busses to 
serve areas not reached by streetcars. Since 
gasoline was critically scarce, a gaseous fuel, 
produced by equipment on each bus, was employ ed 
to operate the motor busses. Eight timber and 
steel bridges were required to complete the system. 
б. Damage to Buildings. Primary blast damage 
put the entire system out of service. Buildings 
and equipment at Sendamachi and Yagurashita, 
6,400 and 900 feet distant from GZ, respectively, 
were structurally damaged by blast. Fires that 
followed completed the destruction at Yagurashita, 
but the existence of a firebreak north of Senda- 
machi prevented the ignition of its buildings. The 
converting equipment at Sendamachi was repaired 
by 9 August 1945. 
c. Damage to Rolling Stock. Of the 123 trolley 
cars operated by the company, 20 percent were 
damaged by fire and 45 percent by blast. Of the 
85 motor busses, fire damaged 21 percent and 
blast 26 percent. Radiant heat from the bomb 
ignited cars and busses within 1,500 feet of GZ. 
Total damage to cars extended a maximum of 
5,700 feet from GZ, heavy damage to 8,400 feet 
and slight damage to 12,500 feet. Busses were 
totally damaged at 4,000 feet and heavily damaged 
5.500 feet from GZ. 
d. Damage to Overhead System. Blast and fire 
damaged 11.4 miles of the overhead transmission 
system including damage to 500 wood and 100 
steel poles. No damage occurred to concrete 
poles, the nearest of which were 6,000 feet from 
GZ. Wood poles were damaged at a maximum 
distance of 4,500 feet from GZ, and steel poles at 
3.500 feet. Overhead transmission cable was 
downed by blast at 8,000 feet. 
e. Damage to Track. With the exception of the 
bridge crossings no damage occurred to the track 
system. 
3. The Government Railroad System 
The government railroad of Japan was the only 
21 system providing intercity transportation for Hiro- 
shima. It maintained the double-track roadbed 
called the Sanyo Main Line as well as classifica- 
tions yards, repair facilities, transit sheds, and 
complete station facilities at Hiroshima. A single- 
track roadbed connected with Ujina (the only 
deep-water harbor in the area) to provide rail-to- 
ship transportation for military materiel and per- 
sonnel being shipped to continental Asia and other 
theaters of operations. Transit sheds and stations 
were also maintained at Koi and Yokogawa, 
intermediate points within Hiroshima, Yokogawa 
being the terminal point of the Kabe line. The 
average passenger rate per month was 1,824,960 
persons, while the average tonnage in freight 
handled was 9,300 tons, requiring 620 cars. How- 
ever, 6,000 cars per month were shunted through 
the yards. The roadbed in the area was a fill 
section with gravel ballast, using 100-pound rails 
and having a track gage of 3 feet 4 inches. The 
Sanyo line crossed the branches of the Ota River 
to the north of the city, thereby limiting the 
number of bridges to four major and several minor 
traffic over crossings. 
a. Building Damage. The majority of buildings 
within the classification and repair area which were 
between the radii of 8,000 and 10,000 feet from 
GZ were superficially damaged by blast, while 
most of those in the station area between the radii 
of 5,800 feet and 7,400 feet were structurally 
damaged by fire and blast. 
b. Locomotive Damage. There was no damage 
to locomotives other than glass breakage. 
c. Car Damage. Of the 700 freight cars in the 
Hiroshima division, 45 were damaged by fire and 
46 by blast, amounting to 13 percent of the total. 
Of the 91 passenger cars, 6 were damaged by fire 
and 77 by blast, or 93 percent of the total, and of 
the 16 electric cars, 6 were damaged by fire and 6 
by blast, or 75 percent of the total. The maxi- 
mum limit of probable damage to freight cars was 
approximately 6,800 feet from GZ, and since 93 
percent of the passenger cars were damaged within 
the 6,800-foot radius and 75 percent of the electric 
cars were damaged at 6,300 feet, the maximum 
limit for passenger and electric cars was beyond 
6,800 feet from GZ. No passenger cars were 
found beyond the limits stated. 
d. Track Damage. There was no damage to 
trackage or bridge crossings, but because of 
adjacent fires and blast debris on the tracks, the 
railroad between Koi and Hiroshima stations was 
closed from 6 to 8 August. Communications and 
signalling facilities were not operative because of 
damage to the communications office in the station 
area. 
e. Cost. The total cost of damage to the 
government railroads as estimated on 15 Novem- 
ber 1945, was 15,800,000 yen or $3,950,000 at the 
rate of exchange of 4 yen to a dollar. 
f. Casualties. Of the 8,467 persons employed, 
198 were killed, 140 were missing, 934 were 
seriously injured and 1,195 sustained minor 
injuries. 
4. Electric Generating and Distribution System 
The Chugoku Electric Company supplied the 
city of Hiroshima with power and light, purchas- 
ing all its electrical energy from the Nippon 
Electrical Co., and selling it to consumers for 
lighting, heating and motor energy. The total 
daily consumption was 80,000 kilowatts for 
lighting and 170,000 kilowatts for heating and 
motor energy. By the end of September when all 
substations were operative, 40,000 kilowatt-hours 
a day were used for lighting and 10,000 kilowatts 
for motors and heating. These figures represent 
an 80 percent over-all reduction in the use of 
electricity. 
a. Sources of Power. Hiroshima was only a 
part of the area served by the Nippon Electric Co., 
which maintained and operated six hydroelectric 
plants having a total capacity of 94,200 kilovolt- 
amperes and one steam-electric plant of 90,000 
kilovolt-amperes. These high tension systems were 
united at the Hiroshima substation rated at 
108.000 kilovolt-amperes. They transmitted power 
to the Hiroshima harbor substation (rated at 
12.000 kilovolt-amperes) on the west side of 
Hiroshima, which distributed the electrical energy 
through 7 substations in Hiroshima having a total 
capacity of 34,800 kilovolt-amperes. The Chugoku 
Electric Co. operated a steam-electric plant rated 
at 3,500 kilovolt-amperes to augment the Senda- 
machi street railway substation. All generating 
and transforming equipment of both companies 
was manufactured in Japan but was based on 
designs originating with the Westinghouse and 
General Electric companies in the United States. 
h. 55- and 110-kilovolt Transmission Systems. 
The Nippon Electric Co. transmitted all electric 
power by overhead transmission from the hydro- 
electric plants to the substations at 110 kilovolts. 
Overhead power transmission from the Saka steam 
plant was maintained at 55 kilovolts. This plant 
was approximately 4.5 miles from the substation. 
22 The 55- and 110-kilovolt transmission systems 
were undamaged. 
c. 3.3- and 22-kilovolt Distribution Systems. The 
substations of the Chugoku Electric Co. trans- 
formed from 22 to 3.3 kilovolts for consumer dis- 
tribution except for the Toyo Industries, Japan 
Foundry, Hiroshima Electric Railway Co., and 
the Mitsubishi Shipyard and heavy industries 
which, having their own substations, received 
power at 22 kilovolts and transformed to required 
voltages. Both overhead and subsurface systems 
for the 22-kilovolt distribution were employed. 
The overhead consisted of approximately 95,000 
feet of 3-phase system. The subsurface consisted 
of 95,000 feet of 3-phase system with pole-mounted 
transformers for feeder distribution. 
d. Damage to Distribution Systems. Approxi- 
mately 70 percent of the 3.3-kilovolt overhead and 
feeder distribution system was damaged by blast 
and fire. Of the 7,000 poles in service, 4,000 wood 
poles and 27 lattice-steel poles were damaged by 
blast and fire. No concrete poles were damaged. 
Overhead wires were downed by blast 8,000 feet 
from GZ. Of the remaining undamaged 30 per- 
cent of the distribution system, only 90 percent 
was usable because some areas beyond the points 
of damage could not be serviced with electricity 
because of lack of connections to substations. The 
damage to the substations of Otemachi and Send- 
amachi made them inoperative and the areas they 
serviced were distributed among the other sub- 
stations. There was no damage to the 22-kilovolt 
subsurface system. 
e. Damage to Equipment and Buildings. The 
equipment in the substations of the Nippon Elec- 
tric Co., 15,000 and 14,300 feet from GZ, respec- 
tively, was undamaged. Of the seven substations 
of the Chugoku Electric Co., the Sendamachi sub- 
station and the steam-electric plant at 7,700 feet 
from GZ were heavily damaged by fires which 
spread to the area. The Otamachi substation, 
2,400 feet from GZ, was heavily damaged by blast 
and fires started by the short-circuited equipment. 
The Dombara, Misasa, and Elba substations were 
only slightly damaged at distances of 5,500 feet and 
beyond from GZ. The damage to the Sendamachi 
substation would have been greatly reduced by 
adequate fire protection. The remaining two sub- 
stations were undamaged. The Nippon Electric 
Co’s. Hiroshima substation (15,000 feet from GZ) 
received minor blast damage, while the Hiroshima 
Harbor substation (14,300 feet from GZ) was un- 
damaged. The office building of the Chugoku 
Electric Co. (2,300 feet from GZ) was structurally 
damaged by blast. 
/. Cost. The estimated cost of damage to the 
Chugoku Electric Co. was 10,000,000 yen, or 
$2,500,000 at the rate of exchange of 4 yen to a 
dollar. 
g. Casualties. Of the 600 persons employed by 
the company, 100 were killed, 100 were injured, and 
50 were missing. 
5. Telephone Communications System 
The Bureau of Telephones of the Governmental 
Communications Department administered and 
operated all telephone communications within and 
through the city of Hiroshima, which was divided 
into two districts. The central district exchange 
(2,000 feet from GZ) maintained a manually oper- 
ated system with 5,500 subscribers, and the west- 
ern district exchange (3,300 feet from GZ) 
operated a dial-type system with 3,400 subscribers. 
The average traffic per month was 3,240,000 local 
calls and 435,000 long-distance calls. All long- 
distance calls were routed through the central 
district. Telephones and equipment were of 
Western Electric design and Japanese manufac- 
ture. 
a. Transmission Systems. The transmission 
system consisted of both overhead and subsurface 
systems. The central district maintained 104,790 
feet of overhead cable carried by 4,958 poles and 
30,232 feet of conduit-encased subsurface cable. 
The western District maintained 53,660 feet of 
overhead cable carried by 2,493 poles, and 9,770 
feet of conduit-encased cable. All subsurface 
cable was buried 4 feet below ground elevation. 
Intersections occurred at manholes of which there 
were 223. Because of the number of branches of 
the Ota River, 18 bridge cable crossings and 9 
subriver crossings were necessary. Subriver cable 
was buried 4 feet below river bottom. 
b. Overhead Transmission Damage. Approxi- 
mately 80 percent of all the overhead system was 
damaged by blast and fire: 97,280 feet of cable and 
4,551 wood poles were damaged in the central dis- 
trict; and 51,280 feet of cable and 2,293 wood 
poles in the western district. A 10 percent salvage 
value was estimated. Wood polos were damaged 
by blast at 4,500 feet from GZ and burned at 
6,500 feet. Cable was stripped from hangers at 
8,000 feet. 
c. Subsurface Transmission Damage. The si di- 
surface system at 4 feet below ground elevation 
would have been intact if it had not been exposed 
23 to exterior damage at bridge crossings and exit 
points to the overhead system. There was no 
blast damage to the conduits and manholes carry- 
ing this system. Damage, however, to Bridges 
6, 13A, 21, 24, and 29, as well as damage to cable 
exit points on conversion to overhead, put approxi- 
mately 80 percent of the subsurface system out of 
service but most of the cable was salvageable. By 
15 August 1945, 35 pairs of subsurface cable had 
been repaired and were available for use. 
d. Building and Equipment Damage. The cen- 
tral exchange (building 43), 2,000 feet from GZ, 
suffered complete minor damage from blast and 
fire; fire from short circuits destroyed 100 percent 
of the equipment. The western exchange (build- 
ing 85), 3,300 feet from GZ, received minor damage 
principally from blast, and 50 percent equipment 
damage from short-circuit fire. It is believed that 
the enclosed type of equipment used in this build- 
ing greatly reduced the short-circuit fire hazard. 
e. Cost. The estimated cost of damage to tele- 
phone communications by the attack was approxi- 
mately 10,000,000 yen or $2,500,000 at the rate of 
4 yen to a dollar. 
j. Casualties. Of the 900 persons employed, 350 
were killed, injured, or missing. 
6. Water Supply System 
The city of Hiroshima maintained a water 
supply system capable of furnishing 20,000,000 
gallons of filtered water a day. All water was 
pumped from the Ota River 3 miles north of the 
city center to a reinforced-concrete, earth-cov- 
ered, camouflaged reservoir of 4,500,000 gallons 
on a hill elevation of 165 feet, 2 miles north of the 
city center. From the reservoir there was a 
gravity flow to the distribution system with two 
booster pumping stations on main feeder lines, 
and a third at Koi where a 234,000-gallon, rein- 
forced-concrete water tower was maintained. 
Each housed a 3,600-gallon-per-minute, electri- 
cally driven pump rated at 30 horsepower. Water 
mains varied in diameter from 4 to 30 inches. 
The water pressure in the center of the city was 
40 pounds per square inch, but at dead-end mains 
at the south end of the city it was only 5 pounds. 
The fire department took water from the distri- 
bution system through below-ground hydrants by 
means of special connectors and from regular 
above-ground two-way hydrants. The water sup- 
ply and distribution system served approximately 
90,000 dwellings and buildings and had always 
proved adequate for peacetime use; no improve- 
merits had been made for wartime emergencies. 
Supplementary sources of water were numerous, 
including about 100 static water reservoirs scat- 
tered over the city, the Ota River and its six 
branches and many open surface drains. In 
addition to the water distribution system, 85 
percent of the dwellings had dug or drilled wells, 
equipped principally with hand pumps. 
a. Damage to Equipment and Buildings. Dam- 
age to the pumping station at 14,000 feet was 
slight glass breakage, and to the purification plant 
at 9,000 feet from GZ was 100-percent superficial 
blast damage. No fires occurred in these areas. 
One motor in a pump house was burned out be- 
cause of falling debris and the metering equipment 
in a meter station suffered heavy damage. The 
booster pumping station equipment was damaged 
only slightly, but the wood-frame buildings of 
stations 1 and 2, which wore 2,900 and 3,600 feet, 
respectively, from GZ, were structurally damaged 
by blast. 
h. Damage to Piping. Eight leaks in the mains 
were attributed to the attack by the Hiroshima 
water department officials. Upon inspection, it 
was the opinion of the team that one leak was 
developed by action of Bridge 22 which was 
directly affected by the blast, and that the remain- 
ing leaks resulted from falling debris. The mains, 
which were designed for pressure of 250 pounds 
per square inch and were buried four feet below 
ground, were undamaged. Approximately 70,000 
branches, one-half to four inches in diameter, were 
fractured or dislocated when buildings were damaged 
by blast and fire. One cast-iron pipe (rated at 250 
pounds per square inch) four inches in diameter 
and a few standard hydrants were damaged by 
falling debris. No flush-type hydrants were 
damaged. The hydrants of both types were 
spaced 600 feet apart. Bridge 29 which carried a 
16-inch water main was put out of service, how- 
ever this damage had no effect since a 16-inch 
main across bridge 30A served the same district. 
Bridge 43, carrying a 14-inch main, was also 
damaged by blast and fire, greatly decreasing the 
water volume in the area served. Floods of 17 
September and 5 October 1945 damaged others 
of the 17 overcrossings. 
c. Cost. The cost of damages as estimated 
on 15 November 1945 was 3,000,000 yen or 
$750,000 at the rate of 4 yen to a dollar. 
7. Sanitary and Storm Sewer System 
Because of the delta formation of Hiroshima, 
24 short laterals to the branches of the Ota River 
were used to dispose of 80 percent of the residen- 
tial waste water while the remaining 20 percent 
was carried through branch pipes to the sewer 
mains. Excreta were not disposed of by the san- 
itary sewer but were collected by the city and sold 
as fertilizer. The mains and open flumes were 
designed as storm sewers to carry off a rainfall 
of 2.36 inches per hour. (The recorded maximum 
was 7.87 inches per hour.) 
a. Pumping System. Pump stations were used 
to pump water from the open ditches to the bay 
areas when, because of high tides, gates could not 
be opened to permit gravity flow. Electric 
motors and manufactured-gas-driven engines were 
used as power units for the pumps, the manufac- 
tured gas being produced at each station. Since the 
gates which permitted gravity flow of water when 
open, or pumping operations when closed, were 
manually operated, a station attendant was re- 
quired in each case to operate equipment and gates 
to keep the rising waters under control. The 
water level in the rivers often reached to within 
one foot of the tops of the revetments during 
flood stages. 
b. Pipe Lines. Because of the absence of 
human excreta, concrete pipe and open flumes 
were used extensively. Standard-type manholes 
were constructed at important intersections and 
changes in direction, the flow-line depth being a 
maximum of 10 feet below ground elevation. 
The sewer system was composed of 211,230 linear 
feet of open flumes of various sizes, 3,170 feet of 
48-inch-diameter clay pipe, 5,970 feet of 48- and 
30-inch-diameter concrete pipe and 74,980 feet of 
concrete-box pipe of varying sizes. 
c. Eguipment and Building Damage. Of the 14 
pumping stations the equipment in 6 within a 
5,200-foot radius from GZ was heavily damaged 
by blast and subsequent fires. The electric motors 
in stations 1 and 5 were burned out, however, by 
debris from blast damage falling into operating 
motors. The remaining stations received slight 
or no damage from the attack. The electric sub- 
stations supplying power to the pumping stations 
were also damaged and could supply no electricity. 
Two of the buildings were structurally damaged by 
blast and five by fire. One building received 
superficial damage by blast and the remaining 
buildings were damaged to a minor degree. Al- 
though the loss of the system was not too greatly 
felt at that time because of the fair weather and 
low water, little or no effort was made to repair 
the damage to the stations, despite the fact that 
they were not damaged severely. As a result, the 
seasonal rains caused floods which inundated the 
revetted areas of Hiroshima and brought the water 
table from its usual level to within 3 feet of ground 
elevation. That condition caused serious delay 
in repairing other utilities which utilized sub- 
surface systems and manholes. The mains and 
flumes were not damaged, although the latter 
were clogged by debris in many places. 
d. Cost. The city engineers estimated the cost 
of damage to the sanitary and storm sewer system 
as of 15 November 1945 at approximately 
3,000,000 yen or $750,000, at the rate of 4 yen to 
a dollar. 
8. Domestic Gas System 
Approximately 75 percent of the 90,000 resi- 
dences and buildings in Hiroshima used 1,125,000 
cubic feet of producer gas a day at a heat content 
of 404 B. t. u. per cubic foot of gas. The producer 
plant was designed by the Japanese to use equip- 
ment of both domestic and foreign manufacture. 
The storage facilities consisted of 2 gas holders, 
6,500 feet from GZ, having capacities of 316,000 
cubic feet and 211,000 cubic feet, respectively. 
All equipment was connected by cast-iron screwed 
pipe with flange and bolt connections. The high- 
pressure system was developed by pumping from 
storage through a station regulator. All gas 
passing through the mains was metered at the 
station. 
a. Piping and Fittings. High-pressure mains 
were cast-iron screwed pipe, and low-pressure 
mains were cast-iron, bell-and-spigot, lead-caulked 
pipes. Pressures of 6 to 8 pounds per square inch 
were maintained in the high-pressure mains and 
were reduced by pressure reducers to 6 to 8 inches 
of water in the low-pressure mains. All piping 
was buried at four feet below ground elevation. 
There were 33,000 feet of high-pressure mains and 
228,600 feet of low-pressure mains. Valves were 
sparsely used throughout the system. Pressure 
reducers were valved between high- and low- 
pressure mains and the mains were valved at the 
producer plants. 
b. Damage to Eguipment and Buildings. Total 
equipment damage by blast was slight. The 
electrical switchboard and recording meters were 
heavily damaged, but no other equipment was 
damaged. Gas holders were damaged when the 
crowns of the tanks were torn by the direct effect 
of the blast and the released gas ignited. The 
25 fires that followed burned timber structures but 
no additional equipment damage was sustained. 
The electrical substation supplying this area was 
also damaged. The 15 buildings dispersed over 
2.7 acres, 6,500 feet from GZ, suffered structural 
damage from blast and fire, and serious superficial 
damage from blast. In addition severe minor 
damage was apparent throughout the otherwise 
undamaged parts. 
c. Damage to Piping and Pressure Regulators. 
There was no apparent damage to the high- or 
low-pressure mains except at bridges. Damage 
occurred to branches leading to buildings or 
dwellings where the latter were damaged. Of the 
27 bridges acting as overcrossings, four were 
damaged by blast and fire, and eight were dam- 
aged by floods. Of the pressure regulators in- 
stalled in the system, two were heavily damaged 
by blast and fire, the most distant being 1,700 
feet from GZ. This damage does not establish 
the limit of effectiveness, because the low-pressure 
mains served by the producers would be affected 
in a degree proportionate to the damage to the 
producers. 
d. Cost. The estimated cost of repair and re- 
placement was 300,000 yen or $75,000.00 at the 
rate of 4 yen to a dollar. 
L. DAMAGE TO STACKS 
Hiroshima contained numerous stacks of rein- 
forced concrete, brick and steel, averaging less 
than 70 feet in height and designed to serve small 
industries and public buildings. Very few stacks 
in excess of 100 feet in height had been built in 
the city proper. Investigation showed the stacks 
to be generally well designed, but frequently 
poorly constructed. Analysis of data based on 
66 stacks revealed those of reinforced concrete to 
be the most effective in withstanding the blast of 
an atomic bomb. Brick proved highly vulnerable, 
and steel appeared most subject to damage. 
It was estimated that within a concentric area 
of an 8,700-foot radius from GZ (beyond which 
no further damage to stacks was encountered) 
15 percent of the concrete, 50 percent of the brick, 
and 70 percent of the steel stacks were damaged 
sufficiently to render them unusable without 
almost complete rebuilding. In all cases the 
cause of damage was believed to be blast. Com- 
putations for MAE’s, using the average-circle 
method, gave mean areas of effectiveness of the 
atomic bomb for structural damage by blast 
against stacks of reinforced concrete, brick, and 
steel, less than 70 feet high, as 0.3, 2.7, and 4.1 
square miles, respectively. The mean effective 
radii were 1,625, 4,900, and 6,050 feet. 
M. PROBABLE EFFECTS ON OTHER 
TARGETS 
1. Targets 
The residential, much of the commercial and 
business sections, and the older industrial sections 
comprising the major portions of the cities of the 
United States and Europe are built up predom- 
inantly with load-hearing, masonry-wall and wood- 
frame buildings. Through many of these areas 
local transportation is by streetcar and bus, and 
above-ground systems are used for telephone 
lines and electric power and lighting. Power 
plants, domestic gas plants, pumping stations, 
and railroad classification and repair yards have 
been overrun by the expanding perimeter of the 
growing cities and are now scattered throughout 
the city areas. Because of the construction used 
and the disposition of critical parts of the urban 
complex, these cities are extremely vulnerable to 
air-burst atomic bombs. Studies presented in 
other parts of this report strongly indicate that an 
atomic-bomb attack against occidental cities 
would result in tremendous loss of life, collapse 
and destruction of most of the wood-frame build- 
ings and load-bearing, brick-wall buildings, and 
almost complete disruption of exposed and con- 
gested transportation, service, and utilities sys- 
tems. In summarizing some of the findings at 
Hiroshima, the following general conclusions are 
pertinent in considering probable effects on targets: 
a. Blast was the primary cause of damage to 
buildings, bridges, services, utilities, stacks, and 
other man-made structures. Extreme damage, 
however, resulted from fires which burned out 
the central part of the city, some of which were 
primary fires started by radiant heat of the bomb. 
b. The bomb was an extremely effective and 
powerful weapon against buildings, being capable 
of causing severe blast damage at great distances 
as compared with conventional high-explosive 
weapons. 
c. It was less effective against steel and con- 
crete bridges but highly effective against wooden 
bridges. In addition, it clogged the approaches 
of bridges with blast debris from collapsed and 
burning buildings. 
d. It was ineffective against underground in- 
stallations but was highly effective against over- 
26 head utility transmission lines and at conversion 
points from underground to overhead, and at 
utility bridge overcrossings. Utilities, pumping 
stations, pressure regulators, and meter equipment 
were damaged in manner and degree commensu- 
rate with damage to buildings housing them. 
e. It was capable of starting primary fires in 
exposed, easily combustible materials such as 
dark cloth, thin paper, or dry-rotted wood exposed 
to direct radiation at distances usually within 
4,000 feet of the point of detonation (AZ). 
/. It killed and injured persons in numbers 
beyond precedent in the history of destruction 
by a single man-made weapon. 
2. Atomic-Bomb Defense 
Construction may be designed to make cities 
less liable to damage from atomic bombs similar 
to that used at Hiroshima, although future bombs 
will probably be more powerful and will increase 
the area of destruction. It is believed, however, 
that adherence to certain principles established 
by this investigation would tend to reduce damage 
substantially below that which would otherwise 
result, especially in connection with new industrial 
construction although the principles should hold 
in genera] for commercial and residential con- 
struction. In the sections of cities which are 
densely built up with load-bearing, brick-wall 
buildings little or nothing can be done through 
passive defense to protect them from almost com- 
plete devastation by an atomic-bomb attack. 
Conclusions in this summary relating to passive 
defense are concerned principally with reducing 
damage to future structures and their contents. 
The two principles of passive defense of great 
importance in planning, designing, or constructing 
buildings or cities to resist atomic bombs are: 
a. Dispersal. 
b. Bomb-resistant construction. 
(1) Dispersal is most applicable to new construc- 
tion. It reduces the damage from a single weapon 
by increasing the distance between targets to a 
point where the dividends returned in effective 
damage are not commensurate with the total effort 
expended in producing and delivering the weapon 
employed. In consideration of the power of 
atomic weapons, dispersal implies less the distance 
between buildings and more the relocation of 
critical industries in small communities which by 
their size and number would greatly increase the 
effort required to destroy or impair the productive 
capacity of a nation. 
(2) Bomb -resistant construction may be*of sev- 
eral types: 
(а) Underground construction. 
(б) Heavy steel and reinforced-concrete, earth- 
quake resistant construction modified to resist 
large blast forces. 
(3) Effective passive resistance against physical 
damage from an atomic bomb would be successful 
in proportion to the employment of both principles 
outlined above. Specific considerations would be: 
(а) Since there was a comparatively small return 
in immunity at Hiroshima from fire spread among 
combustible buildings averaging one and one-half 
stories with an increase in exposure distance above 
50 feet and, likewise, by a decrease in built-upness 
below 12 percent, residential areas of combustible 
construction should not exceed a density (built- 
upness) of 12 percent or have exposure distances 
of less than 50 feet. Bridges of wood construction 
should have about a 75-foot clearance from com- 
bustible areas to prevent fire spread. 
(б) Natural and man-made firebreaks through 
urban areas and around buildings are effective in 
preventing fire spread and conflagrations. 
(c) Fire departments, pumping stations, elec- 
tric generating plants and substations, and tele- 
phone exchanges should be housed in heavy 
bomb-resistant structures with separate auxiliary 
power units for critical equipment. Utilities 
should be underground loop systems with strongly 
constructed manholes or housings for pressure 
regulators, meters, and control valves. To pre- 
vent short-circuit fires, electric motors, generators, 
and telephone exchange equipment should be 
dustproof. 
id) If bomb-resistant shelter is provided for 
operating personnel, standpipe and hose systems 
would be effective in combatting internal fires in 
buildings. Automatic sprinkler systems inside 
buildings would reduce contents’ damage and open 
sprinkler systems at wall openings would reduce 
fire spread between buildings. The value of all 
systems is predicated on an adequate and contin- 
uous water supply. 
(e) Steel or reinforced-concrete hinged shutters 
are the most effective shields against blast at wall 
openings, but steel-roller shutters are recom- 
mended at openings in interior walls. 
(/) Steel stacks below 75 feet in height are 
easily erected and repaired but reinforced-concrete 
stacks are more resistant to blast forces. Stacks 
over 100 feet high should be round and con- 
structed of reinforced concrete or reinforced brick. 
27 (g) Machine tools in Hiroshima were least liable 
to serious blast and debris damage in lightly 
sheathed, steel-frame buildings and most liable to 
serious damage in load-bearing, brick-wall build- 
ings. The three types of bomb-resistant con- 
struction suggested in paragraph (2) above would 
be equally satisfactory for housing machine tools 
except that in frame construction the machines 
would require strong foundation anchors to pre- 
vent overturning from mass building distortion 
and blast forces. 
N. PHOTOGRAPHIC INTELLIGENCE 
1. Damage Evaluation 
The damage to Hiroshima resulting from the 
atomic-bomb attack of 6 August 1945 is the sub- 
ject of a report issued by the Physical Vulnerability 
Section of the Joint Target Group. The report 
was based on a study of photographic sortie 
3 PR-5M391 of 9 August 1945. The following- 
paragraphs indicate the reliability of the report. 
a. The location of ground zero, as estimated by 
the Joint Target Group report, was approximately 
1,130 feet to the northeast of the actual ground 
zero. The reported probable degree of error was 
plus or minus 500 feet. 
b. The 4-square-mile area of virtually total 
destruction reported by the Joint Target Group is 
substantially correct. One small area of addi- 
tional damage (0.048 square mile) was beyond the 
limits of the photographic coverage avilable for 
the report. 
c. It is impossible from vertical photographs to 
assess internal damage to buildings, the roofs of 
which remain intact, and no attempt was made to 
do so in the Joint Target Group report. It is felt, 
however, that it will be of interest to show the 
figures since practically all concrete buildings 
within the badly damaged area of the city did 
suffer internal damage from fire. 
d. Functional identifications were given to 67 
annotated installations, 51 of which were checked 
by this team. 
Funciional identifiration 
Number of 
installa- 
tions 
Percentage 
of total 
Identified correctly 
26 
50. 9 
Identified incorrectly 
11 
21. 6 
Given similar identification 
4 
7. 9 
Unidentified by P. I. report 
10 
19. 6 
Total _ - 
51 
100. 0 
e. The MAE of a weapon is the probable area 
of a specified type and degree of damage which 
would result, if the weapon were used against an 
area of unlimited extent, completely built up with 
targets of the specified type and construction. 
The Joint Target Group reported the MAE for 
superficial damage to average single and multi- 
story buildings to be 10.7 square miles with the 
Hiroshima atomic bomb. The MAE’s of this 
bomb for structural damage about GZ determined 
by the team are as follows: 
Building classifications 
MAE’s in 
square 
miles 
Radii in 
feet 
Multistory, earthquake-resistant 
Multistory, steel- and reinforced-con- 
crete frame (including both earth- 
quake and non earthquake-resist- 
0. 03 
500 
ant buildings) 
. 05 
700 
1-story, light, steel-frame 
3. 4 
5, 500 
Multistory, load-bearing, brick wall 
3. 6 
5, 700 
1-story, load-bearing, brick wall 
Wood-frame industrial-commercial 
6. 0 
7, 300 
(dimension-timber construction) 
Wood-frame domestic buildings 
8. 5 
8, 700 
(wood-pole construction) 
9. 5 
9, 200 
Residential construction 
6. 0 
7, 300 
Damage to contents 
Since the reported MAE was figured for super- 
ficial damage ami this team’s MAE’s were for 
structural damage no direct comparison of the two 
can he made. Moreover, many of the buildings 
(particularly the wood-pole and wood-frame, 
industrial-commercial types of construction) re- 
ported by Joint Target Group as being of V3 and 
V4 vulnerability (Reference tables) were found 
to be much more vulnerable than Occidental 
buildings included in those categories. 
Number of buildings 
Fire damage to 
contents (per- 
cent) 
39 . 
100 
50-100 
0-50 
0 
15 
3 - 
17 . _ 
Note.—All but 6 buildings were within the burned area. 
28 2. Value of Photo Intelligence to Ground 
Survey 
In Hiroshima there was frequent difficulty in 
establishing the cause of damage since a typhoon 
and floods ravaged the city a few weeks following 
the atomic-bomb attack but before the survey 
team arrived on the scene. Photographs taken 
in the interval between the dates of the attack 
and the typhoon were often used to establish the 
cause of damage when reliable ground information 
was lacking. 
a. When, as often happened, interrogation 
brought out conflicting statements, photographs 
were used to help establish the validity of one or 
the other. 
h. Photographs were used to determine routes 
of travel and for orientation on the field. 
c. Firebreaks in existence before the attack were 
plotted, and isolated areas of damage were located 
from aerial photographs. 
d. It is often impossible or inadvisable for a 
ground survey to complete a detailed study of the 
entire damaged area. In such instances a compre- 
hensive damage analysis done from good quality 
photographs by a competent interpreter will 
accurately indicate the extent and relative degree 
of damage. In order to establish the degree of 
damage in more detail, spot checks can be made 
throughout the area. 
29 Appendix A 
U (PS) 
PHOTO 
SUMMARY 
HIROSHIMA 
30 2-HIROSHIMA-PHOTO SUMMARY 
PRE- ATTACK MOSAIC 
(UNCONTROLLED) 
HIROSHIMA 
PHOTOS OF 13 APRIL 1945 
FEET 
PHOTO I - I (PS) 
SECRET 
SECRET 
731566—47 (Face p. 30) No. 1 H “ HIROSHIMA ~ PHOTO SUMMARY 
POST-ATTACK MOSAIC 
(UNCONTROLLED) 
HIROSHIMA 
PHOTOS OF I I AUGUST 1945 
FEET 
PHOTO 2-H (PS) 
SECRET 
SECRET 
731566—47 (Face p. 30) No. 2 31 Summary 
of structural damage. 
Bldqs. 
Percent 
Cause 
80 
31 
Blast 
81 
None 
Bridges 
40 
55 
Fire. 
50 
None 
51 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
32 Summary 
of strut 
•tural damage 
Bldgs. 
Percent 
Cause 
72 
100 
Blast. 
74 
None 
75 
None 
76 
12 
Blast. 
77 
100 
Mixed. 
78 
50 
Blast. 
79 
69 
Fire. 
129 
None 
Bridges 
25 
15 
Flood. 
26 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
33 Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
70 
100 
Mixed 
Bridges 
10 
15 
Flood. 
11 
None 
26 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - ll AUGUST 1945 
PHOTO SCALE 
34 Summary of structural damage 
Bldgs. 
None 
Percent 
Cause 
Bridges 
41 
None 
42 
100 
Flood 
48 
None 
49 
100 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - II AUGUST 1945 
PHOTO SCALE 
35 Summary of structural damage 
mdps. 
Percent 
Cause 
82 
77 
Blast 
82 
27 
Blast 
84 
100 
Blast 
85 
None 
103 
None 
105 
None 
Bridges 
28 
100 
Flood 
38 
100 
Fire and flood 
39 
100 
Fire and flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
36 Summary of structural damage 
FUdqs. 
Percent 
Cmise 
67 
100 
Blast 
68A 
100 
Blast 
68B 
100 
Blast 
68C 
100 
Blast 
69 
100 
Blast 
Bridges 
27 
None 
28 
100 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
37 Summary of structural damage 
Bldgs. 
Percent 
Cause 
64 
None 
65 
N one 
66 A 
100 
Blast 
66B 
100 
Blast 
66C 
100 
Blast 
66D 
100 
Blast 
Bridges 
8 
None 
9 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — ll AUGUST 1945 
PHOTO SCALE 
38 Summary of structural damage 
Bldgs. 
Percent Cause 
118 
100 Blast 
Bridges 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
102 A 
26 
Blast 
102B 
IS 
Blast 
102C 
66 
Blast 
108 
100 
Blast 
Bridges 
43 
100 
Mixed 
44 
None 
45 
15 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — ll AUGUST 1945 
PHOTO SCALE 
40 Summary of structural damage 
Bldqs. 
Percent 
Cause 
86 
4 
Blast 
92 
100 
Blast 
93 
100 
Blast 
107 
100 
Blast 
Bridges 
30 
60 
Flood 
30 A 
10 
Blast 
34 
100 
Fire 
35 
100 
Flood 
36 
100 
Flood 
37 
55 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — ll AUGUST 1945 
PHOTO SCALE 
41 Summary of structural damage 
Bldgs. 
Percent 
Cause 
1 
41 
Blast 
2 
4 
Blast 
3, 4, 5 
100 
Blast 
6 
None 
7 
84 
Blast 
8 
59 
Blast 
9 
21 
Blast 
10 
100 
Blast 
11 
22 
Blast 
12 
69 
Blast 
13, 14, 17 
100 
Blast 
18 
7 
Blast 
19 
9 
Blast 
20 
1 
Blast 
21 
80 
Blast 
22 
8 
Blast 
23 
11 
Blast 
24 
None 
Blast 
25 
6 
Blast 
41 
None 
42, 94 
100 
Blast 
95 
1 
Blast 
96 
31 
Blast 
100 
None 
101 
100 
Blast 
Bridges 
22, 23 
None 
24 
10 
Blast 
29 
100 
Blast 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
42 Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
38 
None 
39 
None 
40 
None 
44 
39 
Blast 
45 
100 
Blast 
46 
100 
Mixed 
47 
None 
48 
None 
49 
None 
50 
N one 
51 
None 
52 
100 
Mixed 
58 
100 
Mixed 
59 
None 
60 
100 
Mixed 
61 
None 
62 
None 
63 
100 
Blast 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — ll AUGUST 1945 
PHOTO SCALE Summary of structural damage 
Bldgs. 
Percent 
Cause 
no 
100 
Mixed 
120 
None 
121 
70 
Mixed 
122 
None 
133 
None 
134 
None 
135 
None 
Bridge* 
4 
None 
5 
None 
5 A 
N one 
7 
None 
7 A 
None 
12 
None 
13 
25 
Blast and 
flood 
13 A 
100 
Blast and 
31 
60 
flood 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — ll AUGUST 1945 
PHOTO SCALE 
44 Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
None 
Bridges 
33 
70 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
45 Summary of structural damage 
Bldgs. 
Percent Cause 
None 
Bridges 
31 
60 Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - II AUGUST 1945 
PHOTO SCALE Summary of structural damage 
Bldgs. 
Percent 
Cause 
15 
100 
Blast 
16 
None 
26 
None 
27 
6 
Fire 
28 
None 
29 
100 
Blast 
32E 
None 
37 
100 
Blast 
Bridges 
19 
None 
20 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE Summary 
of structural damage 
Flips. 
Percent 
Cause 
53 
100 
Blast 
54 
100 
Blast 
55 
100 
Mixed 
56 
100 
Blast 
57 
100 
Blast 
Fridges 
16 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
48 Summary 
of structural damage 
Bldg 3. 
Percent 
Cause 
Ill 
100 
Blast 
Bridges 
15 
None 
16 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE Summary of struct 
ural damage 
Bldgs. 
Percent 
Cause 
87 A 
100 
Blast 
87B 
None 
88 
100 
Blast 
89 
None 
Bridges 
32 
70 
Flood 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - ll AUGUST 1945 
PHOTO SCALE 
50 Summar 
y of structural damage 
Bldgs. 
Percent Cause 
132 
50 Fire 
Bridges 
N one 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - II AUGUST 1945 
PHOTO SCALE 
51 Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
30 
100 
Blast 
31 
None 
32 A 
None 
32 B 
None 
32 C 
100 
Mixed 
33 
None 
34 
100 
Mixed 
97 
100 
Blast 
98 A 
50 
Blast 
98B 
None 
99 
100 
Blast 
Bridges 
18 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - II AUGUST 1945 
PHOTO SCALE 
52 Summary of structural damage 
Pldgs. 
Percent 
Cause 
32 D 
N one 
32H 
None 
35A 
None 
35B 
None 
36 
27 
Blast 
112 A 
34 
Blast 
112H 
None 
112C 
100 
Blast 
112D 
100 
Blast 
112E 
63 
Blast 
113 A 
100 
Blast 
1130 
None 
113D 
None 
113E 
None 
113G 
100 
Blast 
128 
100 
Blast 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER — II AUGUST 1945 
PHOTO SCALE 
53 Summary 
of structural damage 
Bldgs. 
Percent 
Cause 
116 A 
None 
116B 
None 
lies 
None 
116H 
3 
Blast 
1161 
3 
Blast 
Bridges 
None 
DATE OF PHOTOS 
BEFORE - 13 APRIL 1945 
AFTER - H AUGUST 1945 
PHOTO SCALE 
54 : GROUND 
PHONOS 
' . $ 
55 PHOTO 
l-II (PS) 
PHOTO 
2 II (PS) 
PHOTO 
3-11 (PS) PHOTO 
4 II (PS) 
PHOTO 
5-11 (PS) 
PHOTO 
6-11 (PS) 
57 PHOTO 
7-11 (PS) 
PHOTO 
8-1 r (PS) 
PHOTO 
9-11 (PS) 
58 PHOTO 
10-11 (PS) 
PHOTO 
ii-n (PS) 
PHOTO 
12-11 (PS) 
59 SECTION III 
GENERAL INFORMATION 
Dates of survey , 
FDD Field Team 1 ~~ 
Scope of investigation g2 
Acknowledgment g2 
Difficulties encountered __ g2 
Favorable factor 
Source of data _ _ ' 
g^ EDITOR 
Lieutenant Commander Corsbie 
SERVICES (ASHORE) 
Major Orel! 
SERVICES (SHIP) 
Lieutenant Hunter 
SERVICE 8 UTILITIES 
Lieutenant Commander Piper 
REGIONAL HEADQUARTERS 
INTELLIGENCE 
Lieutenant Reitz 
BRIDGES 
Lieutenant Commander Penna 
UNITED STATES STRATEGIC BOMBING SURVEY 
Physical Damage Division Team 1 
Hiroshima. Japan 
DRAFTING 
Lieutenant Dollar 
ORGANIZATION CHART 
14 October 1945 to 26 November 1945 
BUILDINGS 
Lieutenant (jg) Swiger 
EXECUTIVE OFFICER 
Lieutenant Commander Corsbie 
TEAM CHIEF 
Major Bongham 
LANGUAGE 
Lieutenant Commander Holtom 
FIRE 
Lieutenant Commander Walker 
PHOTO INTERPRETER 
Lieutenant Gardner 
FIRE SPECIALIST 
Major Sanborn 
SPECIAL PROJECTS 
Major Brinkman 1. Dates of Survey 
The survey of Hiroshima was started on 14 
October 1945 and completed on 26 November 
1945. 
2. FDD Field Team 1 
Physical Damage Division Field Team 1 
consisted of the following personnel: 
Maj. J. F. Bangharn, Jr., AC, team chief. 
Maj. E. A. Brinkman, CE, chief engineer. 
Maj. F. J. Sanborn, AC, fire study. 
Maj. J. M. Wolverton, AC, fire engineer. 
Lt. Comdr. R. L. Corsbie, CEC, executive 
officer, architect. 
Lt. Comdr. J. H. Holtom, S (I), language. 
Lt. Comdr. N. C. R. Penna, CEC, civil 
engineer. 
Lt. Comdr. G. P. Piper, CEC, civil engineer, 
Lt. Comdr. C. B. Walker, S (A), fire engineer. 
Lt. E. G. Dollar, A, architect. 
Lt. J. W. Gardner, A, photo interpreter. 
Lt. J. F. Garrison, Jr., A, photo interpreter. 
Lt. H. C. Montgomery, Jr., A, photo inter- 
preter. 
Lt. (jg.) L. W. Galloway, S (O), ordnance 
specialist. 
Lt. (jg.) W. F. Swiger, A, civil engineer. 
Mr. E. M. Hall, civilian, language. 
J. A. Meuenster, ChPhoM, photographer. 
E. G. Anderson, SF2/c, draftsman. 
J. P. Harmon, Y2/c, yeoman. 
C. R. Adamson, Jr., PhoM3/c, photographer 
H. Fagin, S (X) 3/c, draftsman. 
C. A. Schmeider, Y3/c, yeoman. 
E. W. Waller, S (P) 3/c, draftsman. 
Cpl. J. J. Delaney, photographer. 
Cpl. T. K. Matsuura, interpreter. 
Cpl. K. B. Van Beukering, photographer. 
C. Y. Cain, Sl/c, draftsman. 
Pfc. C. A. Cramer, photographer. 
Pfc. G. E. Curtis, photographer. 
Pfc. R. D. Hall, photographer. 
3. Scope of Investigation 
Physical Damage Team 1 was concerned only 
with the assessment of physical damage to Hiro- 
shima and, except where judged pertinent to the 
report, did not attempt to study any other effects 
of the atomic bomb such as medical aspects, effect 
upon morale or civilian defense. The team con- 
fined itself to the study of buildings, machine 
tools, bridges, utilities, services, fire damage, 
stacks; the gathering of intelligence data; and the 
interrogation of witnesses and city officials. Mem- 
bers of the team also conducted surveys of the 
physical damage to the city of Ube and the oil 
refinery at Otake. 
4. Acknowledgment 
Hiroshima was within the zone occupied by the 
United States Army Tenth Corps and Forty-first 
Division, through which clearance had to be made 
before the survey could be begun. They furnished 
valuable aid and information which greatly facili- 
tated the survey. 
5. Difficulties Encountered 
The difficulties that confronted the team in 
attempting to ascertain the facts in connection 
with the extent of damage to Hiroshima were 
important: 
a. Summer through fall is the typhoon season 
in Japan and Hiroshima received a full share of 
damage from these storms. On 17 September 
floods developing from torrential rains washed 
out bridges and caused extensive additional dam- 
age to the already stricken city. Again on 5 
October the typhoon which swept up from the 
Ryukyu island chain took its toll of bridges and 
other installations. This made interrogation the 
principal method by which differentiation between 
bomb damage and flood damage could be checked. 
h. Almost all records and data in the city proper 
were either burned by the fires following the drop- 
ing of the atomic bomb or were lost in the subse- 
quent floods. As a consequence few records were 
obtained and those found were usually discovered 
in the possession of companies located outside the 
damaged areas. Others were prepared by indi- 
vidual persons upon the request of team members. 
c. By the time the team arrived in the field 
many persons who had escaped from the city im- 
mediately after the explosion had returned to 
their former homes and were constructing tem- 
porary residences on the sites. Consequently, 
survey personnel found flimsy wooden and cor- 
rugated-iron shelters interspersed among the 
remains of the former structures. 
d. Attempts to interrogate witnesses who were 
actually in the city when the disaster occurred 
were made difficult by the extremely high loss of 
life and by the immediate dispersal of survivors 
to the outlying areas. Although many persons 
volunteered information, it was established by 
questioning that very few of them had actually 
been in the city at the time of the detonation. 
Moreover, it was difficult to trace specific persons 
62 as possible sources of information, since they had 
either been killed or no record of their whereabouts 
was available. 
e. The work of the team was handicapped to 
some extent by official regulations governing the 
movements of the U. S. S. Sims, which, although 
serving as a headquarters ship for the survey, was 
unable to anchor in Hiroshima Harbor as had 
been originally planned. Although the passage 
into Kure Harbor and Hiroshima Bay had been 
swept by Japanese minesweepers the U. S. S. Sims 
was not permitted to anchor in Hiroshima Harbor, 
as the United States Navy had not declared the 
area open to American vessels. Anchoring in 
Hiro Bay, which offered the closest utilizable 
landing area, and driving from there into Hiro- 
shima entailed a round trip by small boat 
and jeep. Therefore, the actual working day in 
the field began at 0930 hours and ended at 1600 
hours. 
/. Considerable work in connection with field 
notes was accomplished on board the U. S. S. Sims, 
but quarters were so cramped that the actual work 
of writing the report was necessarily delayed until 
the team returned to the United States. 
6. Favorable Factor 
A factor which contributed to the efficiency of 
the survey was that the city of Hiroshima had 
been declared off limits to American troops. 
Toward the end of the survey the city was opened 
to military sightseeing tours, but these were all 
nonstop and nonalight. This enabled field teams 
to have a relatively free hand in conducting 
investigations. 
7. Source of Data 
Data obtained by the team members were 
gathered from plant, city, and prefectural records 
and reports; records drawn up by officials in the 
city, interrogation, photographs, visual observa- 
tion, and records obtained from main offices of 
companies that had branches in Hiroshima. It is 
the opinion of the members of the team that the 
information gathered is accurate and reliable. 
63 SECTION IV 
THE TARGET 
Page 
Geographical description. _ 65 
Climate 65 
Historical background 65 
General description of the modern city 68 
Social conditions 68 
Economic conditions 69 
Public utilities 69 
Railroads 69 
Highways 69 
Streets and bridges 69 
Street railway and busses 69 
Air facilities 71 
Communications 71 
Rivers 71 
Ujina Harbor 71 
Shipbuilding 71 
Hiroshima as a military city 71 
Industries 71 
Government offices 73 
Hospitals 73 
Schools 73 
Photographs 1 73 
Hiroshima as a target for the atomic bomb 73 
Figures 1-8, inclusive. 1. Geographical Description 
a. Hiroshima (lat. 34°24' N., long. 132°28' E.), 
first urban target for an atomic bomb, was the 
seventh largest city in Japan and was located in 
the southwestern portion of the Island of Honshu 
on the shore of the Inland Sea. 
b. The Inland Sea had long been important to 
Japan on three scores: (1) as a calm and safe 
water lane interconnecting Honshu, Shikoku, and 
Kyushu, (2) as a protected anchorage area for 
naval and merchant vessels; and (3) as one of the 
most beautiful scenic areas in the world. The 
southern portion of Honshu which faced the 
Inland Sea was called Sanyo, or “sunny side of 
the mountains,” indicating the prominence and 
respect attached to the area by the Japanese. 
Hiroshima was centrally located along this Sanyo 
coast. 
c. The whole of Japan was divided into eight 
administrative regions, called Chiho Gyoshi. The 
entire southwestern section of Honshu, beyond the 
area encompassing Kobe, Osaka, and Kyoto, forms 
the Chugoku Chiho, or middle kingdom region, the 
administrative center of which was Hiroshima. 
Among the places of importance in the Chiho were: 
Kure, the great naval base, less than 20 miles 
from Hiroshima ; Shimonoseki, the Honshu termi- 
nus of the Kammon Tunnel; Matsue and Tottori, 
on the Japan Sea; and Okayama, Fukuyama, 
Onomichi, Iwakuni, Yamaguchi, and Ube, on the 
Inland Sea. The Chugoku Chiho had neither 
high mountains nor extensive lowland plains, but 
was uniformly rugged country, with steep hogback 
ridges and chasm-like valleys cut by small, swift 
streams. Most of the cities were built along the 
coast at the mouths of streams where silt flats 
had formed. 
d. The Chugoku Chiho comprised five prefec- 
tures (Ken), one of which was Hiroshima Prefec- 
ture, centrally located on the Inland Sea coast. 
Kure and Hiroshima were the primary cities in the 
prefecture, the latter being the administrative 
center of the prefectural government. The Ota 
River, rising in the mountains, flowed generally 
east through the western section of the prefecture, 
thence southward into the Inland Sea at Hiroshima 
Bay. In the valley of the lower reaches of the 
river, alluvial deposits had formed which provided 
sites for small towns, and, at the mouth of the 
river, deltaic islands were the site for the city of 
Hiroshima. Westward and southward from the 
mouth of the Ota along the precipitous shorelines 
were a few small residential and fishing villages. 
Southwest of Hiroshima, 20 miles offshore, was the 
island of Miyajima, one of the scenic spots of 
Japan, a mecca for pilgrims and of interest to 
tourists because of the famous temples, shrines and 
scenery. Eastward from Hiroshima along the coast 
were several towns, the closest being Kaitachi, 
Kure and Hiro, the latter being an extensive and 
well equipped naval base, were about 18 miles 
distant; and Fukuyama and Onomichi were farther 
along the coast in the eastern section of the 
prefecture. 
e. The Ota River delta was made up of six 
islands separated by the channels of the river. 
Except where small rocky islands no more than 700 
feet high, previously offshore, were surrounded by 
the silt deposits, the islands were uniformly flat, 
and about 10 feet above mean low water. The 
natural deltaic formations had been extended by 
dredging and filling operations to satisfy the needs 
of a growing city, and, consequently, the southern 
(or seaward) extremities were more regular in 
shape. It is on these islands and on the flats along 
the mainland river banks that the city of Hiroshima 
was located, surrounded by steep, wooded rises 
except to the south where it faced the Inland Sea. 
2. Climate 
a. In general, an oppressively hot and humid 
summer and a mild winter characterized the cli- 
mate of Hiroshima. The mean annual tempera- 
ture was 57.9° F., which is about the same as that 
of Baltimore, Md. 
b. The latter parts of April and June and the 
entire month of September were the rainy seasons. 
The amount of snowfall during the winter was 
negligible. 
c. Light, warm, southerly winds blew from 
May through October, and northerlies and west- 
erlies prevailed during the remainder of the year. 
The typhoon season was June through October. 
These storms were particularly active during the 
month of September, when winds ranging up to 
75 miles per hour occurred, often accompanied 
by torrential rains and floods. 
3. Historical Background 
a. Originally a small fishing village at the mouth 
of the Ota River, Hiroshima’s history really 
began when Terumoto Mori in 1591 became feudal 
lord of the region including most of what is now 
the Chugoku Chiho. Under his direction the 
Castle of Hiroshima was begun and completed 
in 1594. The erection of the castle assured the 
65 FIGURE l-Df 
66 TOPOGRAPHIC SKETCH MAP 
HIROSHIMA 
67 expansion of Hiroshima from a village into a castle 
town on the delta below the castle. With the 
reestablishment of the Tokugawa clan as shoguns 
of the empire in 1603, Hiroshima castle was 
taken over by the Fukushimas. In 1619 it 
passed into the hands of the Asano family, who 
remained as hereditary chiefs of the castle and 
lords of the region until the Meiji Restoration in 
1868. 
b. The feudal castle was built on the delta at 
the mouth of the Ota River and the castle town 
grew up south of it along the thoroughfare, which 
cut across the deltaic islands, connecting Kyoto 
and Shimonoseki. Hiroshima gradually came to 
assume importance as a communication center 
because of its position on the Inland Sea and 
along the Sanyo highway and subsequent rail- 
road. The deltaic formations were extended to 
make more room for the growing town and to 
enable cultivation of more farm land to feed the 
increasing population. During the first 100 years 
that the Asano family was in possession of the 
region, the land acreage under cultivation was 
doubled. Since that time there have been periodic 
reclamation and expansion projects, the latest 
having been under way at the time of the atomic- 
bomb attack. 
c. The establishment of the prefectural govern- 
ment by the Emperor Meiji in 1868 marked the 
beginning of Hiroshima’s development into a 
modern city. More farm land on the delta was 
taken over for use as residential and industrial 
sites. The delta was again extended to provide 
more land, particularly toward the island of 
Ujina, thereby connecting Hiroshima to an ade- 
quate harbor area. 
d. In the sixth year of the Meiji Restoration a 
military garrison was first established at Hiro- 
shima, but it was during the Sino-Japanese War 
(1894-95) that the city began to assume impor- 
tance as a military center. The Emperor Meiji 
made the castle his residence and general staff 
headquarters during that campaign on the Asiatic 
mainland. The city later served as headquarters 
for the Japanese “Ever Victorious Fifth Army,” 
which conquered Singapore, and the Second Gen- 
eral Army. At the time of the atomic-bomb 
attack there were 24,158 of the Army and 58 of 
the naval forces stationed in the city. 
4. General Description of the Modern City 
a. The brief history of the city of Hiroshima 
shows how it had its origin in a small castle town 
on the northern end of the deltaic islands at the 
mouth of the Ota River and increased in size with 
the natural and man-made extensions of the 
islands. The street pattern, the built-upness, and 
the zone occupancy of the modern city reflected 
its historical growth. 
b. In general, the street pattern was an irregular 
block plan with variations imposed by the logical 
flow of interisland traffic and the irregular shapes 
of the islands. A large portion of the northern 
half of the principal island was taken up by the 
old castle grounds, and the southern portions of 
most of the islands wore used for industrial and 
military purposes. The portions of the three 
central islands immediately south of the castle 
grounds comprised the commercial district where- 
in most of the multistory office and commercial 
buildings were located. 
c. The bulk of the newer commercial and 
government structures was representative of post- 
1923 Japanese construction. These buildings 
were relatively modern in plan and design and 
were substantially constructed. The older struc- 
tures of similar occupancy were more classical in 
appearance and were usually of wall-bearing 
construction. Interspersed among these build- 
ings were the low, flimsily built shops and offices 
of typical Japanese design and structure. Except 
for the more modern factories, which were built 
during or immediately prior to the war and which 
reflected occidental influence, the industries were 
housed in exceedingly vulnerable frame or wall- 
bearing units scattered throughout the city. 
Most of the remaining flat area in the city was 
compactly built up with typical Japanese residen- 
tial or residential-commercial, one-story, wood 
buildings. 
5. Social Conditions 
a. The city was badly overcrowded, with over 
31,600 persons per square mile, which is approxi- 
mately 1.23 times the average density for the 5 
boroughs making up greater New York City, 
despite the fact that almost all residences in 
Hiroshima had only 1 or 2 stories. This popula- 
tion density was largely attributable to the geo- 
graphical limitations imposed by the islands and 
to the fact that such a large percentage of utilizable 
land area within the city was monopolized by the 
Army. 
h. Erom 1888, when the first census recorded 
84,873, to June 1942, when the peak population of 
380,000 was reached, the city steadily grew in 
68 civilian population, and coincidentally increased in 
in physical size with the reclamation of land and 
the incorporation of suburban communities under 
the city government. As the probability of aerial 
attack became more evident, the civilian poupla- 
tion had been decreased to approximately 245,000 
as of 5 August 1945, the day before the attack, due 
to voluntary and government-planned evacuation. 
6. Economic Conditions 
a. The city of Hiroshima was unique among the 
sizable urban communities in Japan in that the 
bulk of its workers was dependent upon employ- 
ment in civil and military governmental agencies 
and small and moderate-sized private enterprises 
which directly performed services required by these 
agencies. Since the Chugoku district did not 
produce enough hydroelectric power, coal, or iron 
to support heavy basic industry, Hiroshima had 
few large industries. Since only 20 percent of the 
Ujina Harbor facilities was available for other than 
military purposes, relatively little trade was pos- 
sible. What surplus of foodstuff was raised in the 
locality was largely disposed of to the Army pro- 
curement agencies and shipped by them. Because 
of the absence of industry and large-scale trade, 
bank deposits in the city scarcely went beyond 
petty, middle-class savings, insufficient as com- 
mercial or industrial capital to accelerate active 
enterprises. 
h. Some concerns with main offices in other 
cities of Japan had established subsidiary branch 
factories in Hiroshima. Such were the Japan 
Steel Works, Toyo Industries, Mitsubishi Indus- 
tries, all relatively new plants, Banks, department 
stores, railroad, newspapers, and numerous other 
small industrial and commercial establishments 
gave employment to many. 
7. Public Utilities 
a. Electricity. Electricity for lighting and in- 
dustrial purposes was furnished by the Chugoku 
Electric Co., which obtained it from Nippon Elec- 
tric. The Japanese reported that all houses in the 
city were equipped with electric lighting. 
h. Gas. The Hiroshima Gas Co. manufactured 
and distributed producer gas for domestic and 
industrial purposes. Approximately 75 percent of 
the residences received service. 
c. Water. Hiroshima had an adequate mu- 
nicipal water supply system for both industrial 
and domestic use, due largely to Army influence. 
Water was taken from the Ota River, purified, and 
distributed to all sections of the city at the rate of 
50 gallons per person per day, which, although ap- 
proximately one-half of the usual United States 
quantitative standard, was sufficient by Japanese 
standards. 
d. Sewage. As a result of the oriental custom 
of using night soil as fertilizer, no sanitary sewers 
were necessary. Hiroshima had an adequate 
storm-water sewer system into which domestic 
waste water was drained. 
8. Railroads (Fig. 3-IV) 
Hiroshima was one of the principal intermediate 
stations on the Sanyo main line of the government 
railway system running along the Inland Sea from 
Kyoto to Shimonoseki, one of the most vital links 
in the Japanese railway networks. A feeder line 
from Kure joined the main line at Kaitaichi. 
Connecting with the Sanyo line at the East 
Hiroshima railroad yards were the branch line to 
Ujina and the Geibi line which extended northeast 
into the interior of the prefecture. The Kabe 
electric railroad line ran northward along the Ota 
River from the Yokogawa Station in Hiroshima. 
One indication of the importance of Hiroshima as 
a rail center was the fact that an average of 6,000 
freight cars per month were shuttled through the 
yards between 1941 and 1945. The yards in- 
cluded roundhouse and engine house facilities. 
9. Highways (Fig. 3-IV) 
The main highway between Osaka and Shimo- 
noseki followed generally along the Sanyo railroad 
route and crossed the Ota River delta at Hiro- 
shima. Another good highway followed along the 
coast to Kure. Secondary roads, not suitable for 
extensive motor traffic, followed northward along 
the valley and interconnected the small hinterland 
towns and Hiroshima. 
10. Streets and Bridges (Fig. 3-IV) 
One of the principal features of the street system 
in Hiroshima was the 45 highway bridges which 
were necessary to connect the islands on which 
the city was built. Principal streets were wide 
enough for 2 to 4 lanes of traffic; secondary streets 
were wide enough for 1 to 2 lanes; and almost all 
streets were paved. 
11. Street Railway and Busses 
The Hiroshima Electric Railway Company 
furnished both streetcar and bus transportation 
to all sections of the city and most outlying towns. 
The service was only fair by comparison with that 
provided in most American cities and equipment 
was largely outdated. 
69 TRANSPORTATION AND 
COMMUNICATIONS 
HIRO S H IMA 
STEAM RAILROAD 
ELECTRIC RAILROAD 
HIGHWAY AND MAIN STREETS 
AIR FACILITY 
NOTE ONL.T PRINCIPAL 
ROADS AND STREETS 
ARE SHOWN. 
FIGURE 3-W 
RIVERS AND HARBORS 
HIROSHI M A 
FACILITIES FOR SHIPS 
FACILITIES FOR LIGHTERS 
AND SMALL CRAFT 
SHIP AND BOAT BUILDING 
I 
70 12. Air Facilities 
A secondary military airfield and small seaplane 
base were located on reclaimed land on the south- 
erly end of one of the deltaic islands. 
1 3. Communications 
a. Hiroshima was an important communica- 
tions center primarily because of its important 
government and military administrative functions. 
About 9,000 telephones were installed in the city 
and trunk linos connected with most of the major 
cities in Japan. 
b. Hiroshima was the seat of one of the seven 
telegraphic bureaus which filtered and censored 
land telegraph messages; all important cities and 
towns were connected by the network of lines. 
c. A powerful, 10,000-watt radio station, JOFK, 
and radio-telegraph station, JHL, were important 
communication instruments for the area. 
14. Rivers (Fig. 4-IV) 
The rivers, dividing the deltaic islands on which 
Hiroshima was built, were important as waterways 
for lighters and small craft which transferred 
cargo between the shops, warehouses and indus- 
tries, and ships at anchor in the harbor areas. 
15. Ujina Harbor (Fig. 4-IV) 
a. Before the harbor at Ujina was developed in 
1889 the nearest port for large ships was on the 
island of Miyajima, 20 miles from the city of 
Hiroshima. Only the smallest lighters and boats 
were able to navigate the shallow river channels 
and come alongside the deltaic islands of the city. 
During the Meiji Restoration and Hiroshima’s 
new importance as the prefectural headquarters, 
a total of 340,000 yen was spent to connect the 
mainland to Ujina Island, to build suitable piers 
and wharfage, and to dredge and improve the 
harbor, 
b. Although not large, the harbor handled 
foreign trade amounting to 500,000,000 yen in 1935, 
and was the major link between Honshu and the 
Matsuyama area of Shikoku, and, following the 
Sino-Japanese War (1894-95), was the major 
embarkation point for troops. The port was 
never opened to foreign vessels. 
16. Shipbuilding 
Mitsubishi Shipbuilding Co. fabricating steel 
cargo vessels of 3,000 tons, and Japan Steel fabri- 
cating submersible Army transports (large sub- 
marines) were war industries. For many years 
the Ujina Island Shipyards had built small wooden 
ships and boats for commercial purposes; during 
the war they constructed landing craft for the 
Army. 
1 7. Hiroshima as a Military City 
a. Historically, Hiroshima had been important 
as a military headquarters since the Sino-Japanese 
War when the Emperor Meiji selected it as a base 
for continental expeditionary forces and as im- 
perial headquarters. It continued as a port of 
embarkation throughout the China Incident and 
World War II. It was the headquarters of the 
Fifth Army and, in 1945, was made headquarters 
of the Second General Army which was respons- 
ible for the defense of the southwestern section of 
the Japanese homeland. The military importance 
of the city can be attributed to three factors: (1) 
location in the midst of the Chugoku District in 
a position relatively invulnerable to land and sea 
attack, (2) good transportation and communica- 
tion facilities, and (3) protected harbor on the 
Inland Sea. 
b. In addition to the more important and larger 
areas indicated on the sketch map (Fig. 5-IV), 
smaller areas of barracks, warehouses, offices and 
the like, located throughout the city, were con- 
trolled by the military. In all, 80 percent of 
Ujina Harbor facilities and 42 percent of the 
utilizable land area of the central portion of the 
city were under the direct jurisdiction of the 
Japanese Army. 
18. Industries (Fig. 6-IV) 
In the pre-Meiji era, small-scale industries 
were developed in the Hiroshima castle town to 
satisfy the needs of a feudal community. Many 
of these, such as small boat building, domestic 
metal casting, rice wine manufacturing, textile and 
clothing manufacture, still remained in modern 
Hiroshima. After the Meiji period, meat packing 
and sewing-needle manufacturing became the 
most important industries. After World War I, 
the city took a leading place in the rubber industry 
and, as World War II began, the ordnance- 
producing Japan Steel Co., the Toyo Aircraft 
Industries, and Mitsubishi Machine Tool, Machine 
and Shipbuilding Industries were developed. 
Hiroshima, however, never became a highly in- 
dustrialized city, and, at the time it was attacked 
with the atomic bomb, there were only three 
companies employing more than 500 persons. 
The relative locations of major industries in the 
city are shown on the accompanying sketch map. 
71 IMPORTANT 
MILITARY AREAS 
HIROSHIMA 
FIGURE 5-W 
MAJOR INDUSTRIES 
HIROSHIMA 
FIGURE 6-3ST 
72 19. Government Offices (Fig. 7-IV) 
Hiroshima was the administrative seat of the 
governments of Hiroshima Prefecture, Chugoku 
District and Shikoku District, as as the mili- 
tary and commercial center for the area. For that 
reason, several of the important structures in the 
city were devoted to office space for the various 
governmental bureaus. Some of the more im- 
portant buildings are shown on the sketch map. 
20. Hospitals (Fig. 7-IV) 
Eight hospitals, including the Red Cross hos- 
pital, governmental, military and private hospitals, 
were within the city limits. The Red Cross hos- 
pital and the Communication Bureau hospital 
were housed in sizable, modern buildings and 
were well equipped. The military and prefectural 
hospitals were in wood-frame structures and the 
remainder consisted of small, private, or special 
treatment institutions. 
21. Schools (Fig. 7-IV) 
The Hiroshima University of Literature and 
Science and Higher Normal School was one of the 
best known and respected Japanese institutions of 
higher learning. In addition to the university, 65 
other schools, including grammar, middle, high 
and technical schools, both public and private, 
were a part of the educational facilities of the city. 
22. Photographs 
On the following pages are prewar photographs 
of Hiroshima which give some impression of the 
built-up density of the city and the types of build- 
ings, parks, and streets which were found there. 
The photos were probably taken before 1930. 
23. Hiroshima as a Target for the Atomic Bomb 
It is considered desirable, as an addendum to 
“The Target.” to summarize the physical charac- 
teristics of the city of Hiroshima which contributed 
to or detracted from its value as a target for the 
atomic bomb: 
a. The city of Hiroshima had received only an 
insignificant amount of prior damage; therefore, 
what damage resulted could be attributed to the 
atomic bomb. 
b. Being built on a deltaic formation, it was 
nearly flat for a distance of 6,000 feet in all direc- 
tions from the aiming point, and for more than 
15,000 feet in the southerly quadrant. 
c. At various intervals within a 6,000-foot radius 
from the aiming point there were enough substan- 
tially constructed, multistory, commercial build- 
ings of representative structural types to allow 
comparative study of the effects. 
d. Because of the prevalence of wood construc- 
tion throughout the city, and the pattern of the 
water courses which formed natural firebreaks, the 
incendiary effects of the bomb could be analyzed. 
e. Wit|dn the area were representative types of 
short-span, fixed bridges in sufficient numbers to 
permit a relative study of the effectiveness of the 
weapon against them. 
j. Hiroshima was well equipped with public 
utilities (water, gas, electricity, sewers) and inter- 
urban transportation so that conclusions could be 
drawn regarding the relative vulnerability of these 
facilities. 
g. The principal feature which detracted from 
the target value was the remoteness of the indus- 
trial concentration from the center of the city. 
73 SCHOOLS, HOSPITALS 
AND GOVERNMENT OFFICES 
HIROSHIMA 
§ PREFECTURAL OFFICE 
HIROSHIMA PRISON 
CHUGOKU CHAMBER 
OF COMMERCE 
0 COURT OF APPEALS 
® DISTRICT COURT 
© CITY HALL 
@ MONOPOLY BUREAU 
® MARITIME TRANSPORT 
BUREAU 
HOSPITALS 
SCHOOLS 
HIROSHIMA COLLEGE OF 
LITERATURE AND 
SCIENCE • 
GOVERNMENT OFFICES 
FIGURE 7-ET ■ 
EARLY PHOTOGRAPHS 
H I R O S H IMA 
NOTE (I) ARROWS SHOW APPROX 
DIRECTION FROM WHICH 
PHOTO WAS TAKEN. 
(2)NUMBERS REFER TO 
PHOTOS ON FOLLOWING 
PAGES. 
FIGURE 8-W 
74 PHOTO 1-lV. Aerial view of the densely built-up area along the Motoyasu-gawa looking upstream. 
Except for very heavy masonry structures, the entire area was devastated. Ground zero of the atomic 
bomb was upper right in the photo, opposite the second bend in the river. 
PHOTO 2-IV. Early 
photograph looking up- 
stream on Motoyasu- 
gawa at Bridge 22 and 
City Commercial Dis- 
play Building (domed 
building) which were im- 
mediately adjacent to 
ground zero. 
75 PHOTO 3-IV. Photo- 
graph of the downtown 
shopping district near 
the center of town. Only 
rubble and a few utility 
poles remained after the 
explosion and the result- 
ant fires. This street 
was equivalent to the 
very famous Tokyo Gin- 
za. Photo was taken 
facing east. 
PHOTO 4-1V. Looking 
north-northeast along 
Tera-machi, the Street 
of Temples. This road 
is considerably wider 
than most roads found 
in residential areas. This 
district was completely 
ruined. 
PHOTO 5-IV. Old 
photo looking north from 
vicinity of T-bridge. The 
picture shows extremely 
combustible wood houses 
along the bank of the 
Ota-gawa, and the char- 
acteristic Jap river craft. PHOTO 6-1V. RADIO STATION JOFK. 
This modern building in the northern sec- 
tion of the city housed the studios, offices, 
and transmitter unit for the JOFK radio 
station. This was one of the few stations 
that operated on over 10,000 watts in the 
Japanese homeland. This building was 
typical in design of most of the modern one- 
and two-story commercial buildings in 
Hiroshima. Additional transmitting unit 
located approximately 5 kilometers north 
of the city was connected by cable. 
PHOTO 7-1V. FORMER IMPERIAL 
HEADQUARTERS. During the Sino- 
Japanese War the Emperor Meiji made 
Hiroshima his headquarters; this building 
within the grounds of the old castle is part 
of his administrative center. Early in the 
recent war this area was the headquarters 
of the 5th Army, and later, the 2d General 
Army, responsible for the defense of south- 
west Japan. 
PHOTO 8-IV. HIROSHIMA UNIVER- 
SITY OF SCIENCE AND LITERA- 
TURE, AND HIGHER NORMAL 
SCHOOL. The Higher Normal School was 
one of two such institutions in Japan. In 
1929 the Hiroshima University was first 
founded and combined with the Normal 
School. This building located 4,500 feet 
from ground zero was completely destroyed. 
77 PHOTOS 9-1V and 10- IV. UJINA HARBOR. This relatively small harbor was developed as port 
for the city of Hiroshima, and has been one of the principal embarkation depots for the Japanese Army 
since the Sino-Japanese War. Only 20 percent of the harbor facilities were available for civilian activities. 
One of the important functions of Ujina Harbor was to act as the base for trade and communications 
with the Matsuyama area on the Island of Shikoku. Passenger steamers plying between Hiroshima, 
Osaka, Etajima and various ports on Shikoku and Kyushu stopped here. Fish is a Japanese dietary 
staple, and a fishing fleet based in Ujina Harbor operated on the Inland Sea. The harbor was never 
open to ships of foreign countries, but reports show that foreign trade amounting to about 500,000,000 
yen was handled at the port by Jap ships in 1935. 
78 Photo 11-IV. NIKITSU SHRINE. 
Nikitsu Shrine, near the foot of Futaba 
Mountain, is a part of Enko Park in north- 
eastern Hiroshima. Although considered 
one of the most beautiful ones in the city, 
in general design it is more or less typical 
of Shinto Shrines found all over Japan. 
The woody hillside is a characteristic design 
feature. 
Photo 12-IV. SENTEI POOL. The Sentei Pool, with its beautiful natural setting, was one 
of the most famous sightseeing and recreation places in Hiroshima. It was located east of the 
castle near the bank of the Kyobashi River. The building shown in the photo was the public 
tea house. 
Shinto shrines, Buddhist temples, and Christian churches were all found in the city of Hiroshima. In State 
Shinto, adopted during the early days of the Meiji Restoration, the emperor had an effective religious weapon 
for obtaining the complete loyalty of his subjects. In addition to State Shinto, there are 13 formal sects of 
the religion with formal systems of worship, and Popular Shinto, the most basic type, which deals with more 
personal problems, such as the success of the rice crop and the welfare of the family. The Buddhist religion 
was imported from China, and has an enormous following in Japan. It is a purely mystical faith. Christianity 
has never been fully sanctioned by the leaders of Japan, and has not had any marked effect on Japanese civiliza- 
tion as it has in other countries. SECTION V 
HIGH-EXPLOSIVE ATTACKS ON HIROSHIMA 
Page 
c 1 
Summary 
Attack of 19 March 1945 
Attack of 30 April 1945 
Figure 1 — Facing p. 82 1. Summary 
a. The attacks of 19 March 1945 by four or 
five Navy planes and of 30 April 1945 by a lone 
B-29 constituted the only aerial action against 
Hiroshima City reported by the Japanese prior to 
the atomic-bomb attack of 6 August 1945. Of the 
two attacks, only the Navy strike is listed by the 
Office of Statistical Control, Headquarters, AAF 
(Table 1). 
b. The 2 small bombs (presumed to be 250 
pounds each) dropped in the attack of 19 March 
1945, together with the 10 500-pound bombs 
dropped in the heart of the city in the attack of 
30 April 1945, give a total weight of 5,500 pounds. 
c. Since the area affected by these attacks later 
suffered severely from the atomic bomb it is 
impossible to evaluate accurately the effective 
damage done. The following figures are therefore 
offered only as a recapitulation of damage figures 
obtained from interrogation of residents and city 
officials. For bomb falls refer to figure 1. 
Of the total buildings damaged, 22 were typical 
Japanese domestic structures, 3 were wood-frame, 
and 1 was of load-bearing, brick-wall construc- 
tion. 
2. Attack of 19 March 1945 
Two small bombs were dropped on Hiroshima 
between 0730 and 0800 (local time) on 19 March 
by four or five carrier-based planes, presumably 
Grummans. Most of the information in connec- 
tion with this attack was ascertained through 
interrogation of Mr. Shintaku, of the east fire 
station, and Messrs. Watanabe and Kobayashi, of 
the city engineering department. 
a. The carrier-based planes came in from the 
northwest and while in the vicinity of the Hiro- 
shima railroad station dropped one bomb in a 
river causing no damage, and one in a residential 
section causing two deaths and destroying two 
houses ol domestic construction. In addition, the 
planes strafed along the railroad tracks but caused 
no damage. For bomb falls refer to figure I. 
3. Attack of 30 April 1945 
Ten 500-pound bombs were dropped on Hiro- 
shima during this attack. The bombs were 
dropped from a lone B-29 on 30 April 1945 at 0655 
(local time) and fell within grid areas 5.H and 6H 
as shown on the bomb plot map, figure 1 included 
in this section. The following data are a summary 
of information gathered through observation and 
interrogation of residents and substantiated on 10 
November 1945 by interrogation of Y. Yamani, 
chief of the west side fire department, and S. 
Nimura, city architect-engineer. Mr. Yamani 
was the most valuable source of information since 
Casualties 
Attack of— 
Killed 
Wounded 
Total 
19 Mar. 1945 
30 Apr. 1945 
2 
10 15 
None reported 
25-30 
2 
35 45 
Damage lo buildings 
Attack of— 
De- 
stroyed 
Minor damage 
Total 
19 Mar. 1945 
2 
22 
None reported 
2 _ 
2 
24 
30 Apr. 1945 
Table 1.—Air attacks on Hiroshima Prefecture 
A/F target 
Date 
i* 
Organ 
Number of 
A/C 
2* 
AB 
2* 
HE 
IB Frag 
Size 
Tons 
Size 
Tons 
20th Urban Area 
22 Apr 1945 
4 May 1945 
28 May 1945 
6 Aug. 1945 
19 Mar. 1945 
do 
8888 
8888 
8888 
8888 
1 
1 
1 
1 
7 
11 
3 
3 
3 
2 
2 
3 
Do . 
Do 
98 
— 
Do 
Navy Airfield 
3 
2 
8 
3 
2 
1 
11 
12 
Navy Bay (ships) 
Do 
do 
Do 
do 
12 
*1 Code < Organization) 8888-Daylight tactical mission. 
*2 Code (HE size): 
2=250 300-lb. GP. 
3= 500 600-lb. GP. 
8= 1,000-lb. SAP. 
98= not indicated. 
81 he had been fire chief at the time of this high- 
explosive bomb attack and had on record a report 
of the resulting fire and the fire-fighting efforts to 
bring it under control. He accompanied the in- 
vestigating party and pointed out the exact loca- 
tion of each bomb fall. Mr. Nimura contributed 
information which checked with Yamani, and 
assisted in locating the bomb falls on the bomb 
plot map. 
a. Inasmuch as the bombs landed within the 
area which later received heavy damage from 
direct and indirect effects of the atomic bomb, 
most evidence was destroyed except the crater 
near the temple from bomb 2 and the crater in the 
street from bomb 5. These two craters were 
partly filled but the diameters indicated that they 
had been caused by 500-pound bombs. 
(1) Bomb 1 made a direct hit on the Nomura 
Life Insurance Building causing serious structural 
damage. The building remained unrepaired and 
was completely burned out by fires resulting from 
the atomic-bomb attack. 
(2) Bomb 2 landed near a temple causing minor 
damage. 
(3) Bomb 3 made a direct hit on a warehouse 
behind the Chugoku Electric Co. and started fires 
which burned for two hours, destroying electric 
wire and cable, transformer oil, paint and a small 
amount of gasoline. This was the only fire dam- 
age caused by the attack. 
(4) Bomb 4 fell in a residential section causing 
structural damage to approximately 20 houses of 
typical Japanese construction. 
(5) Bomb 5 formed a crater in an asphalt-sur- 
faced cobblestone street. 
(6) Bombs 6, 7, and 8 landed in low-density 
residential areas and did little or no damage. 
(7) Bombs 9 and 10 fell in the Hiroshima Uni- 
versity grounds, bomb 9 landing in an open area 
and bomb 10 causing minor damage to a building 
approximately 75 feet distant. 
b. Casualties from all ten bombs were esti- 
mated at 10 to 15 killed and 25 to 30 wounded. 
82 HE ATTACKS ON HIROSHIMA 
LEGEND 
ATTACK 19 MARCH 1945 
ATTACK 30 APRIL 1945 
NOTE NUMBERS NOT REFERRED TO THESE SYMBOLS 
IDENTIFY BUILDINGS COVERED IN SECTION X OF 
REPORT 
HIROSHIMA 
HIROSHIMA PREFECTURE. HONSHU, JAPAN 
K A! TA WAN {BAY} 
s!: * »e •« n»» 
> v>s«:* «*«t ..•* iooo 
HOSiX) fCtVGONiC '3»t> 
HIROSHIMA-KO 
(HARBOR) 
SECRET 
U S STRATEGIC BOMBING SURVEY 
HE ATTACKS 
HIROSHIMA, JAPAN 
figure ra 
731566 O - 47 (Face p. 82) SECTION VI 
THE ATOMIC-BOMB ATTACK 
Page 
Source of information 84 
General 84 
Conditions on morning of attack 84 
Time, altitude and direction of attack 84 
Japanese description of explosion 85 
Eyewitness accounts of explosion 85 
Inactivity of defense and fire-fighting organizations 86 
Estimate of bomb and explosion 86 
Ultra-short-wave transmitters 86 
Diagrams 1-4, inclusive 
83 1. Source of Information 
a. No details of the attack preparations, ap- 
proach to the target, dropping of the bomb, ele- 
ments of the explosive, or method of detonation 
of the bomb dropped on Hiroshima are available 
for this report. It is, therefore, necessary to de- 
scribe the attack as experienced and reported by 
the Japanese themselves. The information con- 
tained in this section was obtained through inter- 
rogation, and from Japanese atomic-bomb reports 
prepared by the Kure Naval District and the 
governor of Hiroshima Prefecture. The originals 
and translations of these reports are on file with 
the Intelligence Section of the United States Stra- 
tegic Bombing Survey. 
2. General 
a. Although Hiroshima Bay and surrounding 
airfields had received several attacks, the city 
itself had experienced no large-scale bombing at- 
tacks prior to the atomic-bomb attack on 6 August 
1945. Residents stated, however, that it was not 
an uncommon sight to see formations of American 
planes pass over the city on their way toward 
other targets. Two small-scale, high-explosive 
attacks had been made on the city: one with four 
or five carrier-based planes on 19 March 1945, 
and the other by a single B-29 on 30 April 1945 
(Sec. V). 
b. Defense plans for the evacuation of personnel 
and construction of firebreaks were drawn up in 
the fall of 1944 when the Japanese people began 
to realize that their island empire was no longer 
beyond the reach of American land-based bomb- 
ers. At the time of the atomic-bomb attack the 
city had entered what was termed the sixth evacu- 
ation period, although just what stage of comple- 
tion this involved is not known. 
3. Conditions on Morning of Attack 
a. The morning of 6 August 1945 was clear with 
a small amount of clouds at high altitude. Wind 
was from the south with a velocity of about 4K 
miles per hour. Visibility was 10 to 15 miles. 
b. An air-raid “alert” was sounded throughout 
Hiroshima Prefecture at 0709 hours. Reports of 
the number of planes causing this alert were con- 
flicting. The governor of the prefecture stated 
that four B-29s were sighted, while the Kure Naval 
District reported three large planes. 
c. The aircraft apparently came out over 
Hiroshima from the direction of Bungo Suido and 
Kunisaki Peninsula, circled the city, and withdrew 
in the direction of Harima-Nada at 0725 hours. 
“All-clear” was sounded at 0731 hours. 
d. The following circumstances account in part 
for the high number of casualties resulting from 
the atomic bomb: 
(1) Only a few persons remained in the air-raid 
shelters after the “all-clear” sounded. 
(2) No “alert” was sounded to announce the 
approach of the planes involved in the atomic- 
bomb attack. 
(3) The explosion occurred during the morning 
rush hours when people had just arrived at work 
or were hurrying to their places of business. This 
concentrated the population in the center of the 
city where the principal business district was 
located. 
(4) Many persons residing outside the city were 
present for reasons of business, travel and pleasure. 
(5) National volunteer and school units were 
mobilized and engaged in evacuation operations. 
4. Time, Altitude and Direction of Attack 
(Diagram 1) 
a. Although some confusion exists as to the 
exact time of the explosion, it is safe to state that 
it took place within a minute before or after 
0817 hours. 
b. Although no air-raid “alert” sounded, the 
planes committed in the attack were sighted as 
early as 0806 hours when Matsunago lookout 
station reported two enemy planes proceeding 
northwest. This was corrected to three planes 
at 0809 hours. 
(1) The sound of aircraft engines from the 
direction of Saijo was picked up by Nakano 
searchlight battery at 0814 hours. 
(2) Enemy aircraft were reported over Saijo 
proceeding west at 0815 hours. (Nakano search- 
light battery reported sighting two aircraft flying 
700 to 1,000 feet apart at 23,000 feet, heading 
southwest. Diagram 2.) 
c. Planes arrived over Hiroshima at an altitude 
of 28,000 feet. There were varying reports on 
the number of planes, but it was generally agreed 
that three aircraft were sighted—one plane was in 
the lead, and two followed abreast separated by a 
distance of 700 to 1,000 feet. The lead plane was 
seen to change course to the right while the two 
following planes were observed at 0817 hours to 
release parachutes and turn to the left. Nakano 
searchlight battery reported the release of an 
object attached to a parachute which failed to 
open. At this moment the bomb detonated. 
84 d. Following the detonation, the lead plane was 
seen heading east or northeast. Nothing further 
was reported concerning the activities of the other 
two planes, although one light aircraft was sighted 
heading south at a low altitude. 
e. It was not definitely established which plane 
dropped the bomb, but it was presumed by the 
Japanese that the lead plane carried the bomb 
since the two following aircraft released para- 
chutes. 
5. Japanese Description of Explosion 
a. Survivors of the atomic-bomb attack stated 
that the detonation seemed like a vast combustion 
of magnesium filling the entire sky. These 
persons reported that the flame contained various 
colors such as greenish-white and yellowish-red. 
Reports of the duration of the flash varied from 
instantaneous to 2 to 4 seconds. At the same 
time an overpowering heat wave emanated from 
the source of the flash. 
b. The entire city of Hiroshima was darkened by 
a dense pall of smoke and dust, which limited 
visibility to a few feet. From a distance, a 
mushroom-shaped cloud was seen expanding and 
covering the entire city. It then rose, reaching a 
height of 23,000 feet 4 minutes after the explosion. 
The column began to disintegrate after 8 minutes, 
the top of the mushroom separating itself from the 
column and remaining intact. The color of the 
column was gray and white while the ball on top 
was white tinged with crimson. 
c. In the center of the city a violent blast of air 
immediately followed the flash, knocking down 
trees and poles, stripping branches off trees, tear- 
ing sheets of galvanized metal off buildings, 
derailing streetcars, and squashing or knocking 
over houses. 
d. A slight interval between the flash and the 
blast was noted by persons who were removed 
from the center of the city. 
e. Few persons in the downtown area heard any 
noise of explosion. They were aware only of a 
blinding flash and the overpowering heat and wind. 
Outside the city, however, a loud rumbling noise 
was heard. 
f. Fires soon broke out throughout the city and 
developed into an engulfing inferno in the central 
area of destruction. Some of the fires were 
caused by direct ignition of thatched roofs, cur- 
tains, trees, and the like but the majority resulted 
from secondary effects. 
g. Directly after the explosion survivors re- 
ported finding in some places a “substance” which 
emitted a weak, bluish-white fluorescent light. 
This substance, upon contact, burned through or 
ignited combustible objects. When it fell upon 
clothing it burned through to the flesh, producing 
water blisters which gradually diffused and be- 
came extremely painful. 
h. Following the explosion, strong, changeable 
winds arose, attaining velocities of 25 to 35 miles 
per hour. Whirlwinds were reported at a few 
poin ts. 
i. While the fires were spreading, there was a 
light rainfall throughout the central part of the 
city, with occasional heavy showers in the north- 
western section. 
6. Eyewitness Accounts of Explosion 
a. A Kure Navy Yard war worker who was 2% 
miles west of Hiroshima at the time of the explo- 
sion stated, “I saw a single enemy airplane flying 
over Hiroshima. It released (or fired) a brilliant 
object. I thought at first that it was an incen- 
diary bomb, but then I saw someting that looked 
like a smoke ring from a funnel gradually falling 
toward the ground. It grew larger almost imme- 
diately and increased in brilliance and soon cov- 
ered an area almost equal to that of the city of 
Hiroshima. A flame appeared which was even 
brighter than the sun. I thought I might get 
hurt so I fell flat on the ground.” 
b. Two Kure Navy Yard war workers who were 
located 6 miles northwest of Hiroshima when the 
bomb exploded said: 
We felt a blast of hot air accompanied by a bright 
light. Looking at the sky immediately afterward we 
noticed an enemy plane in the center of a dark-colored 
column, surrounded by the blue of the sky. The column 
undulated. At two places in the column we noticed white 
smoke which gradually expanded. We fell to the ground 
and heard a loud explosion. White smoke could be seen 
rising in the direction of Hiroshima. 
c. A technician from Kure Navy Yard who was 
at Hiroshima Railroad Station, Advance Ter- 
minal, said: 
I noticed what appeared to be an enemy B-29 turning 
to the right at a high altitude as it proceeded north 
directly overhead. Immediately afterward I saw what 
seemed like an incendiary bomb exploding to the rear of 
the plane (in the sky to the south). It was followed by a 
flash (1 to 2 seconds in duration). Thinking it was an 
incendiary bomb, I started to take shelter in the station 
building but had gone only a few steps when I felt a tre- 
mendous concussion strike me from behind. I immedi- 
ately fell to the ground and covered my face. 
85 7. Inactivity of Defense and Fire-Fighting 
Organizations 
a. Fire-fighting and defense units were helpless 
against the explosion and resultant fires. About 
70 percent of the fire-fighting equipment was 
destroyed but the remainder was usable. An 
appeal for help was made immediately to fire com- 
panies outside Hiroshima, hut it was not until 
approximately 1100 hours that this help was able 
to get through to the outskirts of the city. No 
attempt was made to fight fires in the center of 
the city and all equipment was engaged in attempt- 
ing to control fires on the outskirts. 
b. Air defense, civilian defense, and neighbor- 
hood volunteer units completely disintegrated. 
Escape from the surrounding confusion and agony 
was the thought foremost in the minds of the sur- 
vivors. A few individuals did engage in immedi- 
ate first-aid work, but it was not until afternoon 
that it was possible to mobilize personnel 
in sufficient numbers to administer first aid 
extensively. 
8. Estimate of Bomb and Explosion 
a. The Japanese estimate of the center of the 
detonation was determined by the same method 
that the survey team followed. Ground zero was 
ascertained by careful study of the flash-burns and 
blast marks on trees and houses throughout the 
city, from which the direction of blast was calcu- 
lated. Air zero was computed by taking the 
angles of elevation of shadows formed on scorched 
surfaces by opaque obstacles in the paths of the 
radiated rays. The Japanese calculated the 
center of the explosion to be at an elevation of ap- 
proximately 1,800 feet over a point 980 feet south 
of the Gokoku Shrine, between Aioi Bridge and 
Karniya-cho. (The survey calculated AZ to bo 
2,000 feet.) 
b. The only conclusion immediately reached 
about the bomb itself was that it was an extremely 
powerful explosive of an heretofore unused type. 
It was only after the announcement by American 
radio stations that an atomic bomb had been 
dropped on Hiroshima that the Japanese became 
aware of the atomic characteristics of the missile. 
9. Ultra-Short-Wave Transmitters 
a. The ultra-short-wave transmitting units 
dropped by parachutes at approximately the time 
the atomic bomb was released were objects of in- 
tensive study by the Japanese (diagrams 3 and 4). 
The exact relationship between the transmitting 
units and the bomb itself was not discovered. 
b. Tin 'ee of these transmitting sets were found 
in unbroken condition in the mountains 12% miles 
north of Hiroshima. The following is a descrip- 
tion of the sets quoted from the Kure Naval 
District report: 
The objects consisted of a light-metal cylinder attached 
to a parachute at one end so that the cylinder could be 
suspended vertically; the lower extremity of the cylinder 
consisted of a transparent plastic hemisphere containing 
a clockwork control mechanism. The cylinder was found 
to contain powerful electric cells and an ultra-short-wave 
transmitting unit. An air-pressure diaphragm was secured 
on the outside and was connected with the electrical 
apparatus and the clockwork mechanism contained in the 
hemisphere and cylinder, thereby constituting a powerful 
transmitting unit which would change the transmitting 
frequency in accordance with external air pressure varia- 
tions. The electrical system of this apparatus was con- 
nected to an antenna which extended from an opening in 
the extremity of the cylinder, and was attached to the 
top of the parachute in such a manner as to extend upward 
toward the top of the parachute * * *. No explosive 
elements were contained in this equipment. 
86 ITAKl 
SEARCHLIGHT 
STATION 
ENVIRONS OF 
HIROSHIMA 
KILOMETERS 
DIAGRAM 1 
87 OBSERVATION OF ENEMY PLANES FROM NAKANO 
SEARCHLIGHT BATTERY 
(6 AUG. ABOUT 0815) 
DIAGRAM 2 
88 ULTRA SHORT-WAVE TRANSMITTER 
ATTACHED TO PARACHUTE 
CHARACTERISTIC CURVE OF PRESSURE- 
FREQUENCY 
(IT WAS FIGURED THAT HANGING WEIGHTS WITH 
A DIAMETER OF 11.8 CM WERE ATTACHED TO 
THE FACE OF THE PRESSURE GAUGE PANEL.) 
DIAGRAM 3 
89 CIRCUIT DIAGRAM FOR ULTRA 
SHORT-WAVE TRANSMITTER ATTACHED TO PARACHUTE 
DIAGRAM 4 
90 SECTION VII 
DETERMINATION OF AIR ZERO 
Page 
Summary - .. 92 
Definition. 92 
Location and elevation 92 
Method 92 
Accuracy.. _ _ 92 
Photos 1 to 4, inclusive. 
Figure 1. 1. Summary 
The point of burst of the atomic bomb is re- 
ferred to as “zero,” a point determined to be in 
grid 5H approximately 700 feet southeast of the 
T-bridge, at an elevation of slightly over 2,000 
feet. The location of zero in both plan and eleva- 
tion was developed from flash marks found on 
surfaces readily scorched or spalled by radiation of 
heat from the explosion. Marks or unscorched 
areas which were delineated by “shadows” on 
surfaces that were shielded by some object in the 
path of the radiation or heat wave afforded direc- 
tions and elevations for the location of the point 
of detonation. 
2. Definition 
The zero point may be defined as the point of 
detonation of the atomic bomb. The point had 
location in both plan and elevation, inasmuch as 
the bomb burst in the air. Throughout this 
report the ground location of the point immedi- 
ately under the burst is designated as ground zero, 
abbreviated to GZ, and the actual point of 
detonation in the air is designated as air zero, 
abbreviated to AZ. 
3. Location and Elevation 
GZ was found to be in grid 5H at coordinates 
744,200-1,261,850 (fig. 1). Air zero, determined 
from an average of seven computations, was found 
to be slightly over 2,000 feet. 
4. Method 
Both AZ and GZ were determined from flash 
marks found on buildings, bridges, and other 
structures or objects. The flash marks resulted 
from the scorching of surfaces such as wood, 
asphalt, paint, or the spalling of granite from 
radiation of the intense heat of explosion. Objects 
obstructing the path of the heat wave cast their 
“shadows” which were actually unscorched areas. 
The edges of the “shadows” upon horizontal 
surfaces led to the location of GZ, and upon 
vertical surfaces permitted the computation of 
AZ. Photos 1 to 4, inclusive, show typical 
flash marks. 
a. Ground zero was located by extending to an 
intersection the lines formed by various flash 
marks on horizontal surfaces. The lines were 
extended by sighting by eye across objects placed 
at two points along the mark and alining stakes 
ahead to a point of intersection with other lines 
similarly extended. Six such lines were run from 
flash marks found on the granite door sill of build- 
ing 6, 600 feet east of GZ; on granite objects in 
the shrine, approximately 800 feet north of GZ; on 
the granite shrine, 900 feet northeast of GZ;on the 
asphalt roadway, 250 feet west of GZ; on the orna- 
mental granite work on building 11, 800 feet 
southeast of GZ; and on bridge 22, 250 feet south- 
west of GZ. Other marks were used to check the 
point obtained by intersection of the lines listed 
above. 
b. Air zero was determined from marks made 
on vertical surfaces, usually outlined by over- 
hanging objects or members which “shadowed” 
portions of the surfaces. The legs of the triangle 
formed a and b in figure 1, were measured with a 
scale or steel tape, and the horziontal distance 
(base line) to GZ was scaled from the map. The 
base line was checked, where practicable, by actual 
measurement on the ground. Thus, similar 
triangles were formed which permitted simple 
calculation of the height of burst, or AZ. Seven 
such computations were made with base lines 
ranging from 600 to 6,600 feet. The marks 
actually used in determining AZ were on a 
granite lantern post at entrance to shrine, 600 feet 
north of GZ; asphalt surface of bridge 20, 2,900 
feet southwest of GZ; wooden window frame of 
penthouse on Electric Building 26, 2,300 feet 
south of GZ; tile wall surface of Electro-Technical 
Laboratory Building 74, 6,000 feet north of GZ; 
asphalt surface of bridge 30, 1,900 feet southwest 
of GZ; asphalt roof of Communications Building 
85, 3,300 feet northwest of GZ; and Gas Holder, 
6,600 feet south of GZ. 
5. Accuracy 
The degree of accuracy attained in locating GZ 
and AZ was limited by circumstance, but it is 
believed to be adequate for the purpose of evaluat- 
ing effects of the bomb. All measurements were 
made from flash marks, which, although easy to 
see, were not sharply defined along the edges. 
This lack of sharp delineation was probably 
caused by the fact that the source was not actually 
a point but an oblate sphere of fire in which the 
major axis was vertical. Elevation measurements 
therefore, could not be made with precision and 
minor inaccuracies were inevitable. 
a. Ground Zero. All points of intersection of 
the lines extended from the six flash marks fell 
well within a circle of 50-foot radius. Although 
the method list'd in the determination may appear 
inaccurate, it must be pointed out that more 
92 precise methods (such as use of a transit and tape 
traverse) would have attained no greater degree 
of accuracy inasmuch as the edges of the flash 
marks were not sharp lines. The selection of the 
edge of the “shadow” was a matter of judgment 
which could nullify the precision of extending a 
line by means of a transit. Surveys made by the 
Japanese (Chugoku Electric Co., and the city 
architect) placed GZ in the same general area as 
that determined by this team. 
b. Air Zero. The seven calculations of AZ 
ranged from 1,600 feet to 2,300 feet and averaged 
slightly over 2,000 feet. This figure is believed to 
be correct within 200 feet. Japanese surveys 
made independently by the Chugoku Electric Co. 
and the city architect established AZ’s of 500 
meters (1,635 feet) and 800 meters (2,620 feet), 
respectively. A survey was also made by the 
Kure Naval District, and the following is taken 
from their report of September 1945, paragraph 
5, page 17: 
The carbonization of timbers in the vicinity of Ushida 
and the Hiroshima University of Literature and Science 
caused by the radiated blast showed comparatively clear 
shadows which were formed by obstacles in the path of the 
radiated rays. From this, the angle and direction of the 
source of the rays were clearly determinable. Taking the 
horizontal distances and angles from these points, the 
altitude of the center of the blast was calculated and 
figures of 580 meters and 510 meters, respectively, were 
obtained. From this, the altitude of the burst was figured 
to be approximately 550 meters * * *. 
The average of the four findings of the Japanese 
was 1,970 feet. The height of AZ as determined 
by the British is taken from the preliminary report 
of the British Mission to Japan, paragraph 2.1.2, 
page 10, which reads as follows: 
Enough measurements, however, were taken in each 
place to confirm the general location of GZ as that marked 
as the center of the circles on the accompanying maps; 
and to give reasonable estimates of the height of burst. 
These are: 
Hiroshima—Just below 2,000 feet. 
Nagasaki—Approximately 1,750 feet. 
These are the distances between GZ and AZ. Since GZ 
was effectively at sea level at both places, they may be 
taken as heights of bursts above sea level. 
The calculations of the British and Japanese 
surveys placed AZ slightly under 2,000 feet, which 
closely approximates the result obtained by calcu- 
lations of this team. 
93 SEC R ET 
LOCATION OF GROUND ZERO(GZ)AS DETERMINED FROM FLASH MARKS 
0 - LOCATION OF JAPANESE DETERMINED 6Z 
(B) - LOCATION OF BRITISH DETERMINED GZ 
TYPICAL CASE OF FLASH MARK USED IN COMPUTATION OF AIR ZERO (AZ) 
U S. STRATEGIC BOAfflING SURVEY 
DETERMINATION OF ZERO POINTS 
HIROSHIMA, JAPAN 
FIGURE l-m 
SECRET 
94 TYPICAL FLASH MARKS 
PHOTO 1 VII. Showing flash marks on asphalt deck 
of bridge. 
PHOTO 2-YII. Showing flash marks on granite lan- 
tern post. 
PHOTO 3-VII. Showing flash marks on celotex- 
type wallboard. 
PHOTO 4—VII Showing flash marks on granite steps 
95 SECTION VIII 
TYPICAL JAPANESE DWELLINGS 
Object of study 97 
Residential areas 97 
The dwelling 97 
Rooms and furnishings 99 
Photographic description, photos 4-19, inclusive 100 j 
Materials 100 
Construction 107 
Blast vulnerability 10/ 
Fire vulnerability H® 
Other photos, 1-3, 20-26,inclusive. 
Figures 1-6, inclusive. 
Page 
96 1. Object of Study 
shelter. Permanency of construction was not 
considered a particularly desirable feature. This 
concept of a dwelling was strengthened by, and 
probably resulted from, his experience with earth- 
quakes, fires, and typhoons which have ravaged 
his country since the beginning of time. Thus, if 
disaster struck, he could rebuild his home at rela- 
tively low cost from local materials. Superstiti- 
tion, which was so closely interwoven with Japa- 
nese tradition, also exerted an influence on the plan- 
ning of his dwelling in the form of “Kimon”, the 
science of conciliating the household gods. Few 
Japanese would build a house before presenting its 
plan to one of the scholars of his “science” to de- 
termine whether or not the various parts of the 
house were auspiciously situated in relation to the 
center, or if misfortune were liable to befall the 
occupants. Favorable dates for starting con- 
struction and moving in were also determined in 
this manner. 
b. Dwellings in Japan varied from the one-room 
hut of the poor to the multi-room mansions of the 
wealthy, therefore no one residence that could be 
designated as typical in all respects. Except for 
a few Western style houses, however, most Jap- 
anese residences were of the same type construc- 
tion and utilized the same materials. The de- 
scription below, therefore, can be applied to nearly 
all Japanese dwellings. 
c. Description. In general, the dwelling was a 
one- or two-story, unpainted, wood-frame struc- 
ture with a heavy tile, wide-eaved roof of graceful 
lines. Exterior walls were straw-reinforced-mud 
plaster on a lath mat of split bamboo. The mud 
was usually finished with a thin coat of fine sand, 
clay, or white lime plaster. Thin boards were 
sometimes placed over the plaster along the lower 
parts of the wall for protection (photos 5-6). On 
one side, large areas of glazing in sliding sashes 
made it possible for the house to be opened up on 
the garden. Sliding sashes with panels of trans- 
lucent, white rice paper were also used for most 
interior doors and partitions. Fixed interior par- 
titions were similar to exterior walls. Floors were 
covered by closely fitting straw mats (Tatami) 
except in passageways, baths, toilets, and kitchens. 
These mats were of a standard size, 6 feet by 3 
feet, and 2 inches thick. Room sizes were referred 
to by the number of mats a room contained. A 
suspended ceiling of thin wood sheets was used 
throughout the house. Neither attics nor base- 
ments were found in Japanese dwellings. Figures 
Although the Japanese had to a great extent 
adopted Western construction practices for their 
industrial, civic and large commercial buildings, 
their dwellings remained of a design and construc- 
tion indigenous to Japan and, therefore, unfamiliar 
to most Americans. Since residences comprised 
the bulk of any urban area, a complete under- 
standing of this type of building was necessary 
before the damage to an urban target, such as 
Hiroshima, could be fully comprehended. It is 
the object of this section to present the data per- 
taining to the typical dwelling, which affected its 
vulnerability to fire and blast weapons, and their 
effects thereon. 
2. Residential Areas 
Residential areas in Hiroshima, like those in 
other Japanese cities, were characterized by a 
high degree of built-upness resulting from a den- 
sity of population comparable to some of the worst 
slum districts in large American cities (photos 1-3). 
Various sizes of one- and two-story, wood-frame 
buildings roofed with tile were built close together 
along the streets, with numerous outhouses, wood 
garden walls and fences to the rear of the houses 
occupying most of the remaining ground area 
within a block. Streets were very narrow and 
laid out in a rectilinear pattern except where topo- 
graphical features interfered. Sidewalks were not 
common, the streets being used for pedestrian as 
well as vehicular traffic. Open gutters carried 
drainage and waste water from houses on each 
side. In areas where the residential section was 
not clearly defined, small combination shop-dwell- 
ings were found, with the shop opening directly 
onto the street and the owners living to the rear 
or in the second story. These buildings, however, 
did not differ from the usual dwellings in details 
of construction. 
3. The Dwelling 
a. Background. The Japanese dwelling was 
developed into its present form to satisfy the need 
for a suitable structure in which to carry out the 
highly traditional family and social life. The 
characteristics of the house which are usually 
criticized by the Occidental (flimsiness of con- 
st ruction and stark simplicity of interior) can be 
explained by the fact that the Japanese found in 
these qualities an answer to his own particular 
needs. His home was not designed to furnish the 
maximum of comfort, but to serve primarily as a 
97 PHOTO l-VIII. Roof- 
line view of Japanese 
residences crowded 
about a small cove on 
the outskirts of Hiro- 
shima. Note the typical 
tile roofs, the nearly uni- 
form height of the houses 
and the high degree of 
built-upness. 
PHOTOS 2 VIII and 3-VII1. 
The high degree of built-up- 
ness that is a characteristic of 
Japanese cities and villages is 
shown in these aerial views of 
typical residential districts. 
The lower photo shows a fish- 
ing village. Its expansion has 
been restricted by high hills 
and overcrowding has resulted. 
98 4-6, inclusive, are drawings of one- and two-story 
dwellings. 
4. Rooms and Furnishings 
a. Flan. The simplest Japanese dwelling con- 
sisted of an entrance, a living room which also 
served as a dining room and bedroom, minimum 
toilet facilities, and a kitchen which might or 
might not be within the main structure. In larger 
homes the plan was expanded to include additional 
rooms similar to the living room, a bath, and, in 
some cases, one room furnished in Occidental style 
(Western room). When these additional living 
rooms were available they ceased to be used as 
multi-purpose rooms and acquired definite func- 
tions such as guest, dining or sleeping rooms. The 
room actually used as a living room probably 
would be the only one which would include a 
“Tokonoma” (recess for ornaments); otherwise the 
rooms would be similar in design and furnishings 
and could be used interchangeably. The different 
types of rooms usually found in a Japanese dwelling 
are described in paragraphs b-h below, and their 
relation to each other can be seen in the plans in 
figures 4 and 6. 
b. Entrance (photo 7). The Japanese residence 
was entered through sliding doors of wood inset 
with panes of either clear or translucent glass. 
These doors, which were at grade level, admitted 
one to the Genkan, a small room similar to a 
vestibule, which provided the transition between 
the street and the interior of the house. The 
finished floor of the house, which was approxi- 
mately 18 inches above grade, extended part wray 
into the Genkan, necessitating an additional step 
between the house floor and the stone or concrete 
floor of the entrance. It was at this step that 
shoes were removed before proceeding into the 
house. A cabinet or a series of shelves were 
provided for tin1 shoes. There was no other 
furniture in the Genkan. Another set of wood 
sliding doors with rice paper panels separated the 
entrance from a hallway which gave access to 
other rooms of the house. In addition to this 
entrance the more expensive dwellings had a 
smaller one for family use only. When two 
Gcnkans were present the larger one was more 
elaborate and some kind of formal decoration was 
generally used. Screens or partitions were so 
placed within the house that the areas used for 
domestic purposes could not be seen from the 
garden. 
c. Lining Room. This room (photos 10-14), 
the largest and most frequently used in the 
residence, was the center of activity, answering 
the purposes of living, dining, and bed rooms. It 
always occupied the most favorable location in 
the house, usually along the side where it could 
overlook the garden and be exposed to the winter 
sun and the summer breeze. At least one and 
more often two of its walls were sliding wood 
sashes with panels of rice paper which could be 
opened or removed entirely, allowing the room to 
merge with those adjacent to it or to open up on 
the garden. Straw mats (Tatami) laid on a thin 
wood subfloor, gave a soft, resilient quality to the 
floor, and accentuated the rectilinear patterns 
which occurred in all walls and openings. A very 
light ceiling of thin wood was suspended over the 
room. It was in the living room that the tradi- 
tional, ornamental recess (Tokonoma) was found, 
usually extending the entire width of the room. 
These recessed areas conformed to certain estab- 
lished proportions and methods of construction, 
but the arrangement of the cupboards (Jibukuro) 
and shelves (Tana) might vary somewhat. Closets 
for clothing and bedding were located in the living 
room or in an adjacent passage. 
d. Living Room Furnishings. The following is 
a list of the articles of furnishings and ornaments 
most often found in a living room. 
(1) Dia—A low table used for dining, etc. 
(2) Zabutona—Small cushion scats. 
(3) Hibachi—Charcoal brazier. 
(4) Kakemono—A decorative scroll, hung in 
the tokonoma. 
(5) Jibukuro—Storage cupboards within the 
tokonoma. 
(6) Tana Small shelves for- ornaments, also 
within the tokonoma. 
(7) A small dressing chest with mirrow and 
drawers. 
(8) Various ornaments, such as dolls and 
carvings. 
(9) Bedding At night the bedding was re- 
moved from its closet and spread on 
the floor, thereby converting the living 
room into sleeping quarters. 
(10) Other items, such as large cabinets and 
sewing machines, were occasionally 
found in larger homes, but they were 
not standard furnishings. 
e. The Kitchen (photo 15). The kitchen of the 
Japanese house was a small room, located so that 
it would have direct access to the outside, but 
never in a conspicuous place in relation to the 
99 garden or living room. In some cases it was 
detached from the house. The floor was of wood 
or dirt, and usually one step below the level of the 
other rooms in the house. A small, masonry 
range heated by charcoal was used for cooking 
unless gas was available and within the means of 
the family. This range was crude, consisting of a 
simple firebox into which charcoal was placed and 
ignited through an opening near the bottom. As 
a rule much fanning was necessary before sufficient 
heat was generated to warm the utensil which 
rested on a grate over a circular opening in the 
top of the stove. A sink and drain board were 
built into one wall. Other furnishings included a 
work table, cabinets and shelves for the numerous 
trays, bowls, and dishes. 
/. Toilet [photo 17). The Japanese depended 
upon night-soil for fertilizer to such an extent that 
few flush-type water closets wrere used. The 
toilet (Benjo) was a simple fixture fitted in an 
opening in the floor. Beneath the floor was a pit 
lined with wood or concrete which caught the 
excrement which was collected periodically and 
carted to farms for use as fertilizer. The small 
compartment which the toilet occupied had a tile 
or wTood floor, plaster walls with tile or wood wain- 
scoting, and sliding doors, sometimes opening di- 
rectly onto a passageway. Except in the smaller 
homes, a lavatory was located in an adjoining 
compartment or in a small recess off the passage- 
way. The bath was seldom placed in close prox- 
imity to the toilet and lavatory as is customary in 
the United States. 
g. Bath (photo 16). The room in which the 
Japanese bathed was usually a small, concrete- 
floored room with a wooden tub built into one 
corner. Beneath the tub, which was about 2)2 
feet deep, a charcoal stove was installed to heat 
the water. This stove was usually fired from out- 
side the room. Wood slats were usually placed 
over the concrete floor which drained to an open 
gutter outside the house. Walls were of plaster 
with wood wainscot, although tile for floor, wain- 
scot and exterior of the tub was frequently used 
in more expensive homes. Clothes were removed 
in an adjoining compartment or on a raised section 
of the floor and placed on shelves along the wall. 
The text for Photo 16 describes briefly the pro- 
cedures followed by the Japanese when bathing. 
As all Japanese could not afford to have bath 
rooms in their homes, public baths were main- 
tained in cities and towns. 
h. Western Rooms. Japanese in the higher- 
income brackets usually furnished one room of 
their residence in what they referred to as the 
Western style. The typical straw mats were re- 
placed by a hardwood-finish floor; permanent 
partitions were constructed; swinging doors were 
used in place of sliding wall panels; and the room 
was furnished with Western style furniture. A 
false fireplace often completed the “Westerniza- 
tion” of the room. 
5. Photographic Description 
a. The photos on the following pages illustrate 
the principal features of the Japanese dwelling. 
Most of the photos are of a residence considerably 
larger and more expensive than could he afforded 
by the average Japanese family. As indicated in 
paragraph 3b, however, the same materials and 
construction features were found in all Japanese 
dwellings, regardless of cost or size. In this 
respect, therefore, the photos shown can be con- 
sidered typical. 
6. Materials 
a. Wood. An abundance of timber in Japan 
and the natural preference of the inhabitants for 
this medium combined to make wood by far the 
most common material used in the construction of 
dwellings. Temperate zone conifers, which are 
considered the best construction material, were 
found throughout most of Japan and used exten- 
sively. Bamboo was sometimes used for struc- 
tural members in addition to its more common uses 
as drains, laths, siding, and decoration As cut 
lumber was expensive, rough timber was utilized 
to a great extent, being shaped on the job by the 
carpenter. Japan did not have the wide variety 
of dimension lumber found in the United States. 
b. Plaster. This material, which was used for 
exterior panel walls and fixed partitions in most 
Japanese dwellings, was manufactured on the site 
by reinforcing clay or mud with rice straw. It was 
applied on lathing or strips of split bamboo tied 
with straw. A fine sand or white lime plaster was 
usually used as a finish. 
c. Tile. Heavy, vitreous tile was used almost 
exclusively for roofs of residences in urban areas. 
Glazed tile for wainscoting and floors was found 
in some baths, toilets and kitchens. 
d. Glass and Paper. Nonstructural glass and 
thin, translucent rice paper provided the panes in 
windows and doors. Some interior sliding sashes 
were covered with a heavy, opaque rice paper. 
e. Other Materials. Concrete, brick, and stone 
were used to some extent for floors in baths and 
100 PHOTO 4-VI1I. Exterior and 
forecourt of a large Japanese 
residence. Note the elaborate 
tile roof. The wooden shutters 
seen on the right are locked in 
place across all entrances at 
night. 
PHOTO 5-VIII. Another 
view of the above house, show- 
ing large corner window with 
sliding sash. The circular 
window has obscure glass in 
fixed sash. Opening in fence 
to left leads to garden. 
PHOTO 6-VIII. Photo taken 
at rear of same residence. 
The panel walls are mud 
plaster on bamboo lath with a 
white lime plaster finish. The 
bamboo wainscot protects the 
plaster. Note the numerous 
roofs and the half-timber con- 
struction. 
101 PHOTO 7-VII I. ENTRANCE. 
The entrance (Genkan) of a large 
Japanese residence. The photo was 
taken just inside the exterior doors. 
PHOTOS 8-V1II and 9 VIII. INTERIOR 
PASSAGE. Interior view of passage along 
garden side of house from the entrance. The 
sliding sash on both sides of the passage allows 
the rooms to be opened to the garden. The 
relation of the rooms to the garden can be 
seen in the photo below. 
102 PHOTO 10-VIII. Living room 
showing a Buddhist image in- 
corporated into the design of 
a tokonoma. 
LIVING ROOM : Note that in the above photo the inclusion of the budsudan has not altered the basic 
proportions of the tokonoma, which are standarized. The cabinet containing the budsudan is called 
a butsurna. The Japanese warm their hands over the charcoal brazier, or hibachi, which is the only 
source of heat in most dwellings. Photo 11 shows one variation in the arrangement of the jibukuro, 
the cupboards in which small articles for the living room are stored. The table with the revolving top 
is of heavy wood with a lacquer finish, and of a somewhat better quality than is found in average 
homes. The dolls in the tokonoma are popular forms of decoration in Japan. 
PHOTO ll-VIII. In- 
terior view showing the 
furnishings of a Japanese 
living room. 
103 PHOTOS 12-VIII and 13-YIII. Photo- 
graphs and sketches of interior and fur- 
nishings of a living room. Construction 
and materials are typical but the quality 
is above average. 
PHOTO 14-VIII. THE BED. This 
photo of a Japanese bed shows the ease 
with which a living room can be converted 
into sleeping quarters. The bed consists 
of two heavy blankets similar to our com- 
forters. When not in use they are stored 
in the closets on the right. A low mirrored 
dressing table (not shown here) completes 
the bedroom furnishings. The unshaded 
light bulb is typical. 
104 PHOTO 15-VIII. KITCHEN. This kitchen 
was described as modern by the owner. Located 
to the left of the sink was a typical masonry 
firebox with two grated openings in the top. In 
such stoves charcoal is placed, ignited, and 
fanned to provide heat for cooking. Cabinet 
space in the kitchen provided storage for utensils. 
PHOTO 16-VIII. BATH. The ritual of the bath in 
Japan consists of lathering, washing, and rinsing before 
entering the tub of very hot water to soak and relax. 
Floors, tubs, and wainscots of wood are more common 
than tile. Slatted wood floors drain the water from the 
sponge bath. A charcoal stove, fired from the outside, 
heats the water. 
PHOTO. 17-VIII. TOILET. Flush-type water closets are 
seldom found in Japanese residences. The Benjo shown in the 
photo is a porcelain fixture through which the excrement falls into a 
pit where it is collected and carted away to farms for use as fertilizer. 
Large homes usually have a lavatory built in a small recess off the 
hallway near the Benjo. In more modest residences the Benjo is 
often located near the kitchen and the sink used for washing in lieu 
of a lavatory. 
105 PHOTO 18-VIII. A view of one of the 
more elaborate gardens. It is so located 
that it can be seen from all the principal 
rooms of the house. The entire wall of the 
house pictured is of sliding sash which can 
be removed, extending the living area into 
the garden. 
GARDENS: Gardening in Japan has become a highly developed art. So exacting is this art that 
every garden (elaborate as seen in Photo 18 or just a tiny spot of ground) falls into one of the many 
classes under the two general types: Tsukama (artificial hills) and Hira-niaw (level gardens). Each 
is laid out according to established formulae. Religious or philosophical significance is attached to 
the location or shapes of the trees, rocks, miniature hills, etc., which make up the design. There 
is seldom a profusion of color but rather an atmosphere of restraint, for the Japanese strive to create 
in their gardens a refinement so hidden beneath an ordinary outward appearance that oidy those 
with the most cultivated taste can recognize and appreciate it. 
PHOTO 19-VTII. The 
close relationship be- 
tween the living room 
and the garden areas is 
shown in this view of a 
modest home. 
106 kitchens, but were seldom used as structural 
material in the frame of the house. 
7. Construction 
a. General. Residential construction in Japan 
was primarily the work of local carpenters. These 
men were, as a rule, highly skilled especially in 
the use of wood, and their high quality of work- 
manship was displayed in the delicate interiors 
and cabinet work of the dwelling. The practices 
followed, however, placed their residential con- 
struction far below American standards of strength, 
rigidity, and weather tightness. Apparently, sizes 
of members were determined by general practice 
and the materials available rather than by calcu- 
lation of loads and stresses, and members used 
under the same conditions might vary greatly in 
size. A minimum of rough hardware was used, 
the members being joined by intricate joints 
which were cut on the job. These joints tended 
to cause the over-all size of members to be larger 
than those which would be used in American 
construction of a similar type. 
b. Foundations. Most dwellings were supported 
about 12 to 18 inches above the ground by short, 
wood posts resting on individual footings of stone 
or concrete. In better construction, beams be- 
neath exterior walls and major partitions were 
found in addition to individual foundations. As a 
precaution against earthquake, the structure of 
the dwelling usually was not rigidly anchored to 
the foundation, thus reducing to some extent the 
vulnerability of the structure to the effects of 
ground shock. 
c. Frame {jigs. 4 and 5). The frame of the dwel- 
ling consisted primarily of a heavy roof system, 
supported by 4- by 4-inch wood columns spaced 
about 6 feet apart around the exterior and along 
all major partitions. The exterior columns were 
framed into a heavy plate (usually about 9 by 9 
inches). Heavy rough timber beams spanned 
the structure and supported the simple framing 
system of rough poles on which the purlins rested. 
Joints were usually mortise and tenon. No diag- 
onal sheathing or bracing was used in the framing. 
d. Floors. Interior floors not covered by straw 
mats were usually a single thickness of %-inch 
wood flooring. This flooring was nailed to joists 
(approximately 2 by 1% inches) spaced 1 foot 2 
inches on centers. Joists were rough poles of 
about 4-inch diameter. Beams were spaced ap- 
proximately 3 feet on centers, and supported every 
3 to 6 feet along their length by individual foot- 
ings. Where straw mats were used, the wood 
flooring was dropped 2 inches and became a sub- 
floor for the mats. 
e. Walls. Two-inch plaster panels between 
framing members formed most exterior walls of 
dwellings in Hiroshima. The plaster (par. 4b) 
was applied to a lath of split bamboo (%-to 1-inch 
diameter) which was lashed together with twine 
or straw. No insulation or inside sheathing was 
used. However, on some exterior walls a layer of 
thin boards or bamboo up to about 3 feet above 
ground served as protection for the plaster. Few 
walls of concrete, brick or stone were found. 
f. Partitions. Stationary partitions were iden- 
tical to exterior walls except that the protective 
layer of boards was not found. Movable par- 
titions were sliding sash covered with cloth or rice 
paper. 
g. Roof and Ceiling. Nearly all Japanese 
dwellings had hipped or gabled clay tile roofs of 
about 30° pitch. As a rule the tile was set in 
mud on % to K-inch sheathing, but in some cases 
it was wired in place. Open ends of the tile and 
cracks were sealed with mud to insure watertight- 
ness. The sheathing was nailed to 2-by 1%-inch 
rafters which were supported by rough pole purlins 
(3-to 4-inch diameter). Wood straps nailed to the 
purlins supported a series of small strips (1 by 1 
inch) across which the %-inch ceiling boards were 
laid. 
8. Blast Vulnerability 
Experimental data on peak pressures or the 
blast impulses necessary to cause damage of vary- 
ing degrees to Japanese residential construction 
are not available. Because of the differences in 
structural methods, comparison of the vulnera- 
bility to blast of occidental and Japanese residen- 
tial construction is not possible except from actual 
experiments. Consequently, a quantitative eval- 
uation of the vulnerability of Japanese construc- 
tion to blast cannot be made. Rather generalized 
conclusions, however, can be drawn: 
a. Resistance to blast is roughly inversely pro- 
portional to mass and strength. The typical 
Japanese residence (photos 20 and 22) was gener- 
ally a light-frame structure consisting of a rela- 
heavy roof system supported by slender 
columns. Lateral rigidity was normally provided 
by moments developed by mortise and tenon 
joints between columns and roof beams. The 
107 PHOTOS 20-VIII and 21-VIII. These photos show 
exterior views of damaged dwellings which show the typical 
framing of this type of building. Note the simple roof 
system, the lack of diagonal and lateral bracing, and the 
extensive use of unsawed lumber. 
PHOTO 22-VIII. This shows the interior framing de- 
tails of the same type of building described above. 
108 Perspective Sketch 
Sliding 
Sash 
Straw Mats-^ 
Joists-? 
_Section Showing Typical 
Floor And Foundation Posts 
JAPANESE RESIDENCE 
FLOOR SECTIONS 
FIGURE l-3mt 
U.S. STRATEGIC BOMBING SURVEY 
109 Section Thru Mead 
FIGURE 2-VIII. Japanese residence—Walls and 
partitions. 
PHOTO 23-VIII. Damage to this typical wall panel has 
broken away the plaster and exposed the bamboo lath. 
PHOTO 24-VIII. This photo of a residence under construc- 
tion shows workers mixing mud plaster for the walls. The 
straw beside them was used as the binder for the mud. Note 
straw beside them was used as the binder for the mud. 
Note the split bamboo lath between the columns. 
no PHOTOS 25-VIII and 26-YIII. These photos are interior 
views of a dwelling in which can be seen typical roof and 
ceiling construction. The drawing below further illustrates 
this type of construction. 
FIGURE 3-VIII. Japanese residence—Section through roof and ceiling. 
Ill SECRET 
SOUTH ELEVATION 
EAST ELEVATION 
NORTH ELEVATION 
WEST ELEVATION 
CONC. FOOTING 
FOUNDATION PLAN 
FLOORING PLAN 
•PLAN- 
U.S. STRATEGIC BOMBING SURVEY 
SECRET 
ONE-STORY JAPANESE 
FIGURE 4 -3ZBE 
RESIDENCE 
731566 O - 47 (Face p. 112) U.S. STRATEGIC BOMBING SURVEY 
ONE-STORY JAPANESE 
RESIDENCE 
FIGURE 5-m 
SECRET 
SECTION 
113 SECRET 
SOUTH ELEVATION 
EAST ELEVATION 
NORTH ELEVATION 
WEST ELEVATION 
• SECOND FLOOR PLAN 
SECRET 
• FIRST • FLOOR • PLAN • 
U.S. STRATEGIC BOMBING SURVEY 
TWO-STORY JAPANESE 
RESIDENCE 
FIGURE 6-3ZIE 
731566 0 - 47 (Face p. 114) panel walls of mud plaster on bamboo lath were 
only lightly fastened to the framing and were 
frequently stripped without rupturing the frame. 
b. The light weight, slender columns, and weak 
mortise and tenon joints were points of weakness 
which rendered the Japanese residence highly 
vulnerable to damage by blast. Failures com- 
monly resulted either from buckling of external 
columns by blast, or by a mass distortion of the 
structure away from the direction of blast, which 
disrupted the joints between columns and beams. 
Because Japanese residential areas were densely 
built up, walls were usually shielded from blast by 
adjacent buildings. Consequently, failure by 
mass distortion was probably the most character- 
istic damage effect since this could readily result 
from blast impinging on the roofs of buildings. 
9. Fire Vulnerability 
a. General opinion in the United States had 
been that Japanese dwellings were “tinder boxes.” 
Considering the dwellings collectively in their 
natural surroundings in a congested city, this opin- 
ion is well founded; but considering an individual 
dwelling set oil’ by itself, the evaluation is inac- 
curate. 
b. Collectively, Japanese dwellings were ex- 
tremely vulnerable to fire because of the high 
degree of built-upness of residential areas, light 
exterior wood sheathing, broad, open, wood 
eaves and air space under the first floor. All 
these features tend to assist fire spread. On the 
other hand, the heavy tile covering on the roofs 
practically precluded ignition of roofs by flying 
embers. Thatched roofs were found only outside 
city limits or in sparsely built-up areas. 
c. Actually, frequency of fires in individual 
Japanese dwellings was less than one-half that in 
American homes. This situation can be attrib- 
uted to the fact that the Japanese dwelling was 
generally less susceptible to ignition because of 
the lesser amount of combustible furnishings and 
higher moisture content of the wood and furnish- 
ings. In addition, there were fewer internal 
sources of ignition and more careful supervision 
by the occupants. Once a fire progressed beyond 
the stage of incipiency, however, the Japanese 
dwelling burned rapidly. 
115 UNITED STATES STRATEGIC BOMBING SURVEY 
LIST OF REPORTS 
The following is a bibliography of reports resulting from 
the Survey’s studies of the European and Pacific wars. 
Those reports marked with an asterisk (*) may be pur- 
chased from the Superintendent of Documents at the 
Government Printing Office, Washington 25, D. C. 
European War 
OFFICE OF THE CHAIRMAN 
*1 The United States Strategic Bombing Survey: Sum- 
mary Report (European War) 
*2 The United States Strategic Bombing Survey: Over- 
all Report (European War) 
*3 The Effects of Strategic Bombing on the German 
War Economy 
AIRCRAFT DIVISION 
(By Division and Branch) 
*4 Aircraft Division Industry Report 
5 Inspection Visits to Various Targets (Special Report) 
Airframes Branch 
6 Junkers Aircraft and Aero Engine Works, Dessau, 
Germany 
7 Erla Maschinen werke GmbH, Heiterblick, Germany 
8 A T G Maschinenbau, GmbH, Leipzig (Mockau), 
Germany 
9 Gothaer Waggonfabrik, A G, Gotha, Germany 
10 Focke Wulf Aircraft Plant, Bremen, Germany 
I Over-all Report 
Part A 
Part B 
Appendices I, II, III 
12 Dornier Works, Friedrichshafen & Munich, Germany 
13 Gerhard Fieseler Werke GmbH, Kassel, Germany 
14 Wiener Neustaedter Flugzeugwerke, Wiener Neu- 
stadt, Austria 
Aero Engines Branch 
15 Bussing NAG Flugmotorenwerke GmbH, Bruns- 
wdek, Germany 
16 Mittel-Deutsche Motorenwerke GmbH, Taucha, 
Germany 
17 Bavarian Motor Works Inc, Eisenach & Durrerhof, 
Germany 
18 Bayerische Motorenwerke A G (BMW) Munich, 
Germany 
19 Henschel Flugmotorenwerke, Kassel, Germany 
Light Metal Branch 
20 Light Metals IndustryjPart I, Aluminum 
of Germany (Part II, Magnesium 
21 Vereinigte Deutsche Metallwerke, Hildesheim, Ger- 
many 
22 Metallgussgesellschaft GmbH, Leipzig, Germany 
23 Aluminiumwerk G m b H, Plant No. 2, Bitterfeld, 
Germany 
24 Gebrueder Giulini GmbH, Ludwigshafen, Germany 
25 Luftschiffbau, Zeppelin GmbH, Friedrichshafen 
on Bodensee, Germany 
26 Wieland Werke A G, Ulm, Germany 
27 Rudolph Rautenbach Leichmetallgiessereien, Solin- 
gen, Germany 
28 Lippewerke Vereinigte Aluminiumwerke A G, Lunen, 
Germany 
29 Vereinigte Deutsche Metallwerke, Heddernheim, 
Germany 
30 Duerener Metallwerke A G, Duren Wittenau-Berlin 
& Waren, Germany 
AREA STUDIES DIVISION 
*31 Area Studies Division Report 
32 A Detailed Study of the Effects of Area Bombing 
on Hamburg 
33 A Detailed Study of the Effects of Area Bombing 
on Wuppertal 
34 A Detailed Study of the Effects of Area Bombing 
on Dusseldorf 
35 A Detailed Study of the Effects of Area Bombing 
on Solingen 
36 A Detailed Study of the Effects of Area Bombing 
on Remscheid 
37 A Detailed Study of the Effects of Area Bombing 
on Darmstadt 
38 A Detailed Study of the Effects of Area Bombing 
on Lubeck 
39 A Brief Study of the Effects of Area Bombing on 
Berlin, Augsburg, Bochum, Leipzig, Hagen, Dort- 
mund, Oberhausen, Schweinfurt, and Bremen 
CIVILIAN DEFENSE DIVISION 
*40 Civilian Defense Division—Final Report 
41 Cologne Field Report 
42 Bonn Field Report 
43 Hanover Field Report 
44 Hamburg Field Report—Vol I, Text; Vol II, Exhibits 
45 Bad Oldesloe Field Report 
46 Augsburg Field Report 
47 Reception Areas in Bavaria, Germany 
EQUIPMENT DIVISION 
Electrical Branch 
*48 German Electrical Equipment Industry Report 
49 Brown Boveri et Cie, Mannheim Kafertal, Germany 
Optical and Precision Instrument Branch 
*50 Optical and Precision Instrument Industry Report Abrasives Branch 
*51 The German Abrasive Industry 
52 Mayer and Schmidt, Offenbach on Main, Germany 
Anti-Friction Branch 
*53 The German Anti-Friction Bearings Industry 
Machine Tools Branch 
*54 Machine Tools & Machinery as Capital Equipment 
*55 Machine Tool Industry in Germany 
56 Herman Kolb Co., Cologne, Germany 
57 Collet and Engelhard, Offenbach, Germany 
58 Naxos Union, Frankfort on Main, Germany 
MILITARY ANALYSIS DIVISION 
59 The Defeat of the German Air Force 
60 V-Weapons (Crossbow) Campaign 
61 Air Force Rate of Operation 
62 Weather Factors in Combat Bombardment Opera- 
tions in the European Theatre 
63 Bombing Accuracy, USAAF Heavy and Medium 
Bombers in the ETO 
64 Description of RAF Bombing 
64a The Impact of the Allied Air Effort on German Lo- 
gistics 
MORALE DIVISION 
*64b The Effects of Strategic Bombing on German Morale 
(Vol. I and Vol. II) 
Medical Branch 
*65 The Effect of Bombing on Health and Medical Care 
in Germany 
MUNITIONS DIVISION 
Heavy Industry Branch 
*66 The Coking Industry Report on Germany 
67 Coking Plant Report No. 1, Sections A, B, C, & D 
68 Gutehoffnungshuette, Oberhausen, Germany 
69 Friedrich-Alfred Huette, Rheinhausen, Germany 
70 Neunkirchen Eisenwerke A G, Neunkirchen, Ger- 
many 
71 Reichswerke Hermann Goering A G, Hallendorf 
Germany 
72 August Thyssen Huette A G, Hamborn, Germany 
73 Friedrich Krupp A G, Borbeck Plant, Essen, Ger- 
many 
74 Dortmund Hoerder Huettenverein, A G, Dortmund, 
Germany 
75 Hoesch A G, Dortmund, Germany 
76 Bochumer Verein fuer Gusstahlfabrikation A G, 
Bochum, Germany 
Motor Vehicles and Tanks Branch 
*77 German Motor Vehicles Industry Report 
*78 Tank Industry Report 
79 Daimler Benz A G, Unterturkheim, Germany 
80 Renault Motor Vehicles Plant, Billancourt, Paris 
81 Adam Opel, Russelsheim, Germany 
82 Daimler Benz-Gaggenau Works, Gaggenau, Germany 
83 Maschinenfabrik Augsburg-Nurnberg, Nurnberg, 
Germany 
84 Auto Union A G, Chemnitz and Zwickau, Germany 
85 Henschel & Sohn, Kassel, Germany 
86 Maybach Motor Works, Friedrichshafen, Germany 
87 Voigtlander, Maschinenfabrik A G, Plauen, Germany 
88 Volkswagen werke, Fallersleben, Germany 
89 Bussing NAG, Brunswick, Germany 
90 Muehlenbau Industrie A G (Miag) Brunswick, Ger- 
many 
91 Friedrich Krupp Grusonwerke, Magdeburg, Germany 
Submarine Branch 
92 German Submarine Industry Report 
93 Maschinenfabrik Augsburg-Nurnberg A G, Augs- 
burg, Germany 
94 Blohm and Voss Shipyards, Hamburg, Germany 
95 Deutschewerke A G, Kiel, Germany 
96 Deutsche Schiff und Maschinenbau, Bremen, Ger- 
many 
97 Friedrich Krupp Germaniawerft, Kiel, Germany 
98 Howaldtswerke A G, Hamburg, Germany 
99 Submarine Assembly Shelter, Farge, Germany 
100 Bremer Vulkan, Vegesack, Germany 
Ordnance Branch 
*101 Ordnance Industry Report 
102 Friedrich Krupp Grusonwerke A G, Magdeburg, 
Germany 
103 Bochumer Verein fuer Gusstahlfabrikation A G, 
Bochum, Germany 
104 Henschel & Sohn, Kassel, Germany 
105 Rheinmetall-Borsig, Dusseldorf, Germany 
106 Hermann Goering Werke, Braunschweig, Hallendorf, 
Germany 
107 Hannoverische Maschinenbau, Hanover, Germany 
108 Gusstahlfabrik Friedrich Krupp, Essen, Germany 
OIL DIVISION 
*109 Oil Division, Final Report 
*110 Oil Division, Final Report, Appendix 
*111 Powder, Explosives, Special Rockets and Jet Pro- 
pellants, War Gases and Smoke Acid (Ministerial 
Report #1) 
112 Underground and Dispersal Plants in Greater Ger- 
many 
113 The German Oil Industry, Ministerial Report Team 
78 
114 Ministerial Report on Chemicals 
Oil Branch 
115 Ammoniakwerke Merseburg G m b H, Leuna, Ger- 
many—2 Appendices 
116 Braunkohle Benzin A G, Zeitz and Bohlen, Germany 
Wintershall A G, Leutzkendorf, Germany 
117 Ludwigshafen-Oppau Works of I G Farbenindustrie 
A G, Ludwigshafen, Germany 
118 Ruhroel Hydrogenation Plant, Bottrop-Bov, Ger- 
many, Vol. I, Vol. II 
119 Rhenania Ossag Mineraloelwerke A G, Harburg 
Refinery, Hamburg, Germany 
120 Rhenania Ossag Mineraloelwerke A G, Grasbrook 
Refinery, Hamburg, Germany 
121 Rhenania Ossag Mineraloelwerke A G, Wilhelmsburg 
Refinery, Hamburg, Germany 
122 Gewerkschaft Victor, Castrop-Rauxel, Germany, Vol. 
I & Vol. II 
123 Europaeische Tanklager und Transport A G, Ham- 
burg, Germany 
124 Ebano Asphalt Werke A G, Harburg Refinery, Ham- 
burg, Germany 
125 Meerbeck Rheinpreussen Synthetic Oil Plant—Vol. I 
& Vol. II 
Rubber Branch 
126 Deutsche Dunlop Gummi Co., Hanau on Main, 
Germany 
127 Continental Gummiwerke, Hanover, Germany 
128 Huels Synthetic Rubber Plant 
129 Ministerial Report on German Rubber Industry 
117 Propellants Branch 
130 Elektrochemischewerke, Munich, Germany 
131 Schoenebeck Explosive Plant, Lignose Sprengstoff 
Werke GmbH, Bad Salzemen, Germany 
132 Plants of Dynamit A G, Vormal, Alfred Nobel & Co, 
Troisdorf, Clausthal, Drummel and Duneberg, 
Germany 
133 Deutsche Sprengchemie GmbH, Kraiburg, Ger- 
many 
OVER-ALL ECONOMIC EFFECTS DIVISION 
134 Over-all Economic Effects Division Report 
Gross National Product 1 Special papers 
Kriegseilberichte [ which together 
Herman Goering Works I comprise the 
Food and Agriculture I above report 
134a Industrial Sales Output and Productivity 
PHYSICAL DAMAGE DIVISION 
134b Physical Damage Division Report (ETO) 
135 Villacoublay Airdrome, Paris, France 
136 Railroad Repair Y ards, Malines, Belgium 
137 Railroad Repair Awards, Louvain, Belgium 
138 Railroad Repair Y ards, Hasselt, Belgium 
139 Railroad Repair YTards, Namur, Belgium 
140 Submarine Pens, Brest, France 
141 Powder Plant, Angoulerne, France 
142 Powder Plant, Bergerac, France 
143 Coking Plants, Montigny & Liege, Belgium 
144 Fort St. Blaise Verdun Group, Metz, France 
145 Gnome et Rhone, Limoges, France 
146 Michelin Tire Factory, Clermont-Ferrand, France 
147 Gnome et Rhone Aero Engine Factory, Le Mans, 
France 
148 Kugelfischer Bearing Ball Plant, Ebelsbach, Ger- 
many 
149 Louis Breguet Aircraft Plant, Toulouse, France 
150 S. N. C. A. S. E. Aircraft Plant, Toulouse, France 
151 A. I. A. Aircraft Plant, Toulouse, France 
152 V Weapons in London 
153 City Area of Krefeld 
154 Public Air Raid Shelters in Germany 
155 Goldenberg Thermal Electric Power Station, Knap- 
sack, Germany 
156 Brauweiler Transformer & Switching Station, Brau- 
weiler, Germany 
157 Storage Depot, Nahbollenbach, Germany 
158 Railway and Road Bridge, Bad Munster, Germany 
159 Railway Bridge, Eller, Germany 
160 Gustloff-Werke Weimar, Weimar, Germany 
161 Henschell & Sohn G m b II, Kassel. Germany 
162 Area Survey at Pirmasens, Germany 
163 Hanomag, Hanover, Germany 
164 MAN Werke Augsburg, Augsburg, Germany 
165 Friedrich Krupp A G, Essen, Germany 
166 Erla Maschinenwerke, G m b H, Heiterblick, Ger- 
many 
167 ATG Maschinenbau G m b II, Mockau, Germany 
168 Erla Maschinenwerke G m b H, Mockau, German}7 
169 Bayerische Motorenwerke, Durrerhof, Germany 
170 Mittel-Deutsche Motorenwerke G m b H, Taucha, 
Germany 
171 Submarine Pens Deutsche-Werft, Hamburg, Ger- 
many 
172 Multi-Storied Structures, Hamburg, Germany 
173 Continental Gummiwerke, Hanover, Germany 
174 Kassel Marshalling Yards, Kassel, Germany 
175 Ammoniawerke, Merseburg-Leuna, Germany 
176 Brown Boveri et Cie, Mannheim, Kafertal, Germany 
177 Adam Opel A G, Russelsheim, Germany 
178 Daimler-Benz A G, Unterturkheim, Germany 
179 Valentin Submarine Assembly, Farge, Germany 
180 Volkswaggonwerke, Fallersleben, Germany 
181 Railway Viaduct at Bielefeld, Germany 
182 Ship Yards Howaldtswerke, Hamburg, Germany 
183 Blohm and Voss Shipyards, Hamburg, Germany 
184 Daimler-Benz A G, Mannheim, Germany 
185 Synthetic Oil Plant, Meerbeck-Hamburg, Germany 
186 Gewerkschaft Victor, Castrop-Rauxel, Germany 
187 Klockner Humboldt Deutz, Ulm, Germany 
188 Ruhroel Hydrogenation Plant, Bottrop-Boy, Ger- 
many 
189 Neukirchen Eisenwerke A G, Neukirchen, Germany 
190 Railway Viaduct at Altenbecken, Germany 
191 Railway Viaduct at Arnsburg, Germany 
192 Deurag-Nerag Refineries, Misburg, Germany 
193 Fire Raids on German Cities 
194 I G Farbenindustrie, Ludwigshaften, Germany, Vol I 
& Vol II 
195 Roundhouse in Marshalling Yard, Ulm, Germany 
196 1 G Farbenindustrie, Leverkusen, Germany 
197 Chemische-Werke, Huels, Germany 
198 Gremberg Marshalling Yard, Gremberg, Germany 
199 Locomotive Shops and Bridges at Hamm, Germany 
TRANSPORTATION DIVISION 
*200 The Effects of Strategic Bombing on German Trans- 
portation 
201 Rail Operations Over the Brenner Pass 
202 Effects of Bombing on Railroad Installations in 
Regensburg, Nurnberg and Munich Divisions 
203 German Locomotive Industry During the War 
204 German Military Railroad Traffic 
UTILITIES DIVISION 
*205 German Electric Utilities Industry Report 
206 1 to 10 in Vol I “Utilities Division Plant Reports” 
207 11 to 20 in Vol II “Utilities Division Plant Reports” 
208 21 Rheinische-Westfalische Elektrizitaetswerk A G 
Pacific War 
OFFICE OF THE CHAIRMAN 
*1 Summary Report (Pacific War) 
*2 Japan’s Struggle to End the War 
*3 The Effects of Atomic Bombs on Hiroshima and 
Nagasaki 
CIVILIAN STUDIES 
Civilian Defense Division 
4 Field Report Covering Air Raid Protection and 
Allied Subjects, Tokyo, Japan 
■ 5 Field Report Covering Air Raid Protection and 
Allied Subjects, Nagasaki, Japan 
*6 Field Report Covering Air Raid Protection and 
Allied Subjects, Kyoto, Japan 
7 Field Report Covering Air Raid Protection and 
Allied Subjects, Kobe, Japan 
8 Field Report Covering Air Raid Protection and 
Allied Subjects, Osaka, Japan 
9 Field Report Covering Air Raid Protection and 
Allied Subjects, Hiroshima, Japan—No. 1 
*10 Summary Report Covering Air Raid Protection and 
Allied Subjects in Japan 
*11 Final Report Covering Air Raid Protection and 
Allied Subjects in Japan 
Medical Division 
*12 The Effects of Bombing on Health and Medical 
Services in Japan 
*13 The Effects of Atomic Bombs on Health and Medical 
Services in Hiroshima and Nagasaki 
Morale Division 
*14 The Effects of Strategic Bombing on Japanese Morale 
118 ECONOMIC STUDIES 
Aircraft Division 
*15 The Japanese Aircraft Industry 
*16 Mitsubishi Heavy Industries, Ltd. 
Corporation Report No. I 
(Mitsubishi Jukogyo KK) 
(Airframes & Engines) 
*17 Nakajima Aircraft Company, Ltd. 
Corporation Report No. II 
(Nakajima Hikoki KK) 
(Airframes & Engines) 
*18 Kawanishi Aircraft Company 
Corporation Report No. Ill 
(Kawanishi Kokuki Kabushiki Kaisha) 
(Airframes) 
*19 Kawasaki Aircraft Industries Company, Inc. 
Corporation Report No. IV 
(Kawasaki Kokuki Kogyo Kabushiki 
Kaisha) 
(Airframes & Engines) 
*20 Aichi Aircraft Company 
Corporation Report No. V 
(Aichi Kokuki KK) 
(Airframes & Engines) 
*21 Sumitomo Metal Industries, Propeller Division 
Corporation Report No. VI 
(Sumitomo Kinzoku Kogyo KK, Puropera 
Seizosho) 
(Propellers) 
*22 Hitachi Aircraft Company 
Corporation Report No. VII 
(Hitachi Kokuki KK) 
(Airframes & Engines) 
*23 Japan International Air Industries, Ltd. 
Corporation Report No. VIII 
(Nippon Kokusai Koku Kogyo KK) 
(Airframes) 
*24 Japan Musical Instrument Manufacturing Company 
Corporation Report No. IX 
(Nippon Gakki Seizo KK) 
(Propellers) 
*25 Tachikawa Aircraft Company 
Corporation Report No. X 
(Tachikawa Hikoki KK) 
(Airframes) 
*26 Fuji Airplane Company 
Corporation Report No. XI 
(Fuji Hikoki KK) 
(Airframes) 
*27 Showa Airplane Company 
Corporation Report No. XII 
(Showa Hikoki Kogyo KK) 
(Airframes) 
*28 Ishikawajima Aircraft Industries Company, Ltd. 
Corporation Report No. XIII 
(Ishikawajima Koku Kogyo Kabushiki 
Kaisha) 
(Engines) 
*29 Nippon Airplane Company 
Corporation Report No. XIV 
(Nippon Hikoki KK) 
(Airframes) 
*30 Kyushu Airplane Company 
Corporation Report No. XV 
(Kyushu Hikoki KK) 
(Airframes) 
*31 Shoda Engineering Company 
Corporation Report No. XVI 
(Shoda Seisakujo) 
(Components) 
*32 Mitaka Aircraft Industries 
Corporation Report No. XVII 
(Mitaka Koku Kogyo Kabushiki Kaisha) 
(Components) 
*33 Nissan Automobile Company 
Corporation Report No. XVIII 
(Nissan Jidosha KK) 
(Engines) 
*34 Army Air Arsenal & Navy Air Depots 
Corporation Report No. XIX 
(Airframes and Engines) 
*35 Underground Production of Japanese Aircraft 
Report No. XX 
Basic Materials Division 
*36 Coal and Metals in Japan’s War Economy 
Capital Goods, Equipment and Construction Division 
*37 The Japanese Construction Industry 
*38 Japanese Electrical Equipment 
*39 The Japanese Machine Building Industry 
Electric Power Division 
*40 The Electric Power Industry of Japan 
*41 The Electric Power Industry of Japan (Plant Re- 
ports) 
Manpower, Food and Civilian Supplies Division 
*42 The Japanese Wartime Standard of Living and Utili- 
zation of Manpower 
Military Supplies Division 
*43 Japanese War Production Industries 
*44 Japanese Naval Ordnance 
45 Japanese Army Ordnance 
*46 Japanese Naval Shipbuilding 
*47 Japanese Motor Vehicle Industry 
*48 Japanese Merchant Shipbuilding 
OH and Chemical Division 
49 Chemicals in Japan’s War 
50 Chemicals in Japan’s War—Appendix 
51 Oil in Japan’s War 
52 Oil in Japan’s War—Appendix 
Over-all Economic Effects Division 
*53 The Effects of Strategic Bombing on Japan’s War 
Economy (Including Appendix A: U. S. Economic 
Intelligence on Japan—Analysis and Comparison; 
Appendix B: Gross National Product on Japan 
and Its Components; Appendix C: Statistical 
Sources). 
Transportation Division 
*54 The War Against Japanese Transportation, 1941- 
1945 
Urban Areas Division 
*55 Effects of Air Attack on Japanese Urban Economy 
(Summary Report) 
*56 Effects of Air Attack on Urban Complex Tokyo- 
Kawasaki-Yokohama 
*57 Effects of Air Attack on the City of Nagoya 
*58 Effects of Air Attack on Osaka-lvobe-Kyoto 
59 Effects of Air Attack on the City of Nagasaki 
60 Effects of Air Attack on the City of Hiroshima 
119 MILITARY STUDIES 
Military Analysis Division 
61 Air Forces Allied with the United States in the W ar 
Against Japan 
62 Japanese Air Power 
63 Japanese Air Weapons and Tactics 
64 The Effect of Air Action on Japanese Ground Army 
Logistics j. n -a 
65 Employment of Forces Under the Southwest 1 acitic 
Command 
66 The Strategic Air Operations of Very Heavy Bom- 
bardment in the War Against Japan (1 wentieth 
Air Force) 
67 Air Operations in China, Burma, India—World 
War 11 , A . 
68 The Air Transport Command in the W ar Against 
Japan , T 
69 The Thirteenth Air Force in the War Against Japan 
70 The Seventh and Eleventh Air Forces in the W ar 
Against Japan 
71 The Fifth Air Force in the War Against Japan 
Naval Analysis Division 
*72 The Interrogations of Japanese Officials (\ ols. I 
and II) 
*73 Campaigns of the Pacific Wrar 
*74 The Reduction of Wake Island 
*75 The Allied Campaign Against Rabaul 
76 The American Campaign Against Wrotje, Maloelap, 
Mille, and Jaluit (Vols. I, II and III) 
*77 The Reduction of Truk 
78 The Offensive Mine Laying Campaign Against Japan 
79 Report of Ships Bombardment Survey Party— 
Foreword, Introduction, Conclusions, and General 
Summary _ , ,,, 
80 Report of Ships Bombardment Survey Party (En- 
closure A), Kamaishi Area 
81 Report of Ships Bombardment Survey 1 arty (En- 
closure B), Hamamatsu Area 
82 Report of Ships Bombardment Survey Party (En- 
closure C), Hitachi Area 
83 Report of Ships Bombardment Survey 1 arty (En- 
closure D), Hakodate Area 
84 Report of Ships Bombardment Survey 1 arty (En- 
closure E), Muroran Area 
85 Report of Ships Bombardment Survey 1 arty (En- 
closure F), Shimizu Area 
86 Report of Ships Bombardment Survey 1 arty (En- 
closures G and H), Shionomi-Saki and Nojima- 
Saki Areas 
87 Report of Ships Bombardment Survey Party (En- 
closure I), Comments and Data on Effectiveness 
of Ammunition 
88 Report of Ships Bombardment Survey Party (En- 
closure J), Comments and Data on Accuracy of 
Firing 
89 Reports of Ships Bombardment Survey Party (En- 
closure K), Effects of Surface Bombardments on 
Japanese War Potential 
Physical Damage Division 
90 Effect of the Incendiary Bomb Attacks on Japan (a 
Report on Eight Cities) 
91 The Effects of the Ten Thousand Pound Bomb on 
Japanese Targets (a Report on Nine Incidents) 
92 Effects of the Atomic Bomb on Hiroshima, Japan 
93 Effects of the Atomic Bomb on Nagasaki, Japan 
94 Effects of the Four Thousand Pound Bomb on Japa- 
nese Targets (a Report on Five Incidents) 
95 Effects of Two Thousand, One Thousand, and Five 
Hundred Pound Bombs on Japanese Targets (a 
Report on Eight Incidents) 
96 A Report on Physical Damage in Japan (Summary 
Report) 
G-2 Division 
97 Japanese Military and Naval Intelligence 
98 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part I, Comprehensive Report 
99 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part II, Airfields 
100 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part III, Computed Bomb Plotting 
101 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part IV, Urban Area Analysis 
102 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part V, Camouflage 
103 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part VI, Shipping 
104 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part VII, Electronics 
105 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part VIII, Beach Intelligence 
*106 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part IX, Artillery 
*107 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part X, Roads and Railroads 
108 Evaluation of Photographic Intelligence in the Japa- 
nese Homeland, Part XI, Industrial Analysis 
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120 SECRET