SUMMARY OF DAMAGES AND INJURIES

SUMMARY OF DAMAGES AND INJURIES
Both the Hiroshima and the Nagasaki atomic bombs exhibited
similar effects.
The damages to man-made structures and other inanimate
objects was the result in both cities of the following
effects of the explosions:
A. Blast, or pressure wave, similar to that of normal explosions.
B. Primary fires, i.e., those fires started instantaneously by
the heat radiated from the atomic explosion.

C. Secondary fires, i.e., those fires resulting from the collapse
of buildings, damage to electrical systems, overturning
of stoves, and other primary effects of the blast.
D. Spread of the original fires (B and C) to other structures.
The casualties sustained by the inhabitants of both cities
were due to:
A. “Flash” burns, caused directly by the almost instantaneous
radiation of heat and light at the moment of the explosion.
B. Burns resulting from the fires caused by the explosion.
C. Mechanical injuries caused by collapse of buildings, flying
debris, and forceable hurling—about of persons struck
by the blast pressure waves.
D. Radiation injuries caused by the instantaneous penetrating
radiation (in many respects similar to excessive X-ray
exposure) from the nuclear explosion; all of these effective
radiations occurred during the first minute after initiation
of the explosion, and nearly all occurred during the first
second of the explosion.
No casualties were suffered as a result of any persistent
radioactivity of fission products of the bomb, or any induced
radioactivity of objects near the explosion. The
gamma radiations emitted by the nuclear explosion did not,
of course, inflict any damage on structures.
The number of casualties which resulted from the pure
blast effect alone (i.e., because of simple pressure) was
probably negligible in comparison to that caused by other
effects.
The central portions of the cities underneath the explosions
suffered almost complete destruction. The only surviving
objects were the frames of a small number of strong
reinforced concrete buildings which were not collapsed by
the blast; most of these buildings suffered extensive damage
from interior fires, had their windows, doors, and partitions
knocked out, and all other fixtures which were not
integral parts of the reinforced concrete frames burned or
blown away; the casualties in such buildings near the center
of explosion were almost 100%. In Hiroshima fires
sprang up simultaneously all over the wide flat central area
of the city; these fires soon combined in an immense “fire
storm” (high winds blowing inwards toward the center of
a large conflagration) similar to those caused by ordinary
mass incendiary raids; the resulting terrific conflagration
burned out almost everything which had not already been
destroyed by the blast in a roughly circular area of 4.4 square
miles around the point directly under the explosion (this

point will hereafter in this report be referred to as X). Similar
fires broke out in Nagasaki, but no devastating fire storm
resulted as in Hiroshima because of the irregular shape of
the city.
In both cities the blast totally destroyed everything within
a radius of 1 mile from the center of explosion, except for
certain reinforced concrete frames as noted above. The
atomic explosion almost completely destroyed Hiroshima’s
identity as a city. Over a fourth of the population was killed
in one stroke and an additional fourth seriously injured, so
that even if there had been no damage to structures and
installations the normal city life would still have been completely
shattered. Nearly everything was heavily damaged
up to a radius of 3 miles from the blast, and beyond this
distance damage, although comparatively light, extended
for several more miles. Glass was broken up to 12 miles.
In Nagasaki, a smaller area of the city was actually destroyed
than in Hiroshima, because the hills which enclosed
the target area restricted the spread of the great blast; but
careful examination of the effects of the explosion gave
evidence of even greater blast effects than in Hiroshima.
Total destruction spread over an area of about 3 square
miles. Over a third of the 50,000 buildings in the target
area of Nagasaki were destroyed or seriously damaged.
The complete destruction of the huge steel works and the
torpedo plant was especially impressive. The steel frames
of all buildings within a mile of the explosion were pushed
away, as by a giant hand, from the point of detonation. The
badly burned area extended for 3 miles in length. The hillsides
up to a radius of 8,000 feet were scorched, giving
them an autumnal appearance.