There has been great difficulty in estimating the total casualties in the
Japanese cities as a result of the atomic bombing. The extensive
destruction of civil installations (hospitals, fire and police
department, and government agencies) the state of utter confusion
immediately following the explosion, as well as the uncertainty regarding
the actual population before the bombing, contribute to the difficulty of
making estimates of casualties. The Japanese periodic censuses are not
complete. Finally, the great fires that raged in each city totally
consumed many bodies.

The number of total casualties has been estimated at various times since
the bombings with wide discrepancies. The Manhattan Engineer District's
best available figures are:

TABLE A
Estimates of Casualties

Hiroshima Nagasaki
Pre-raid population 255,000 195,000
Dead 66,000 39,000
Injured 69,000 25,000
Total Casualties 135,000 64,000

The relation of total casualties to distance from X, the center of damage
and point directly under the air-burst explosion of the bomb, is of great
importance in evaluating the casualty-producing effect of the bombs. This
relationship for the total population of Nagasaki is shown in the table
below, based on the first-obtained casualty figures of the District:

TABLE B
Relation of Total Casualties to Distance from X

Distance Total Killed per
from X, feet Killed Injured Missing Casualties square mile
0 - 1,640 7,505 960 1,127 9,592 24,7OO
1,640 - 3,300 3,688 1,478 1,799 6,965 4,040
3,300 - 4,900 8,678 17,137 3,597 29,412 5,710
4,900 - 6,550 221 11,958 28 12,207 125
6,550 - 9,850 112 9,460 17 9,589 20

No figure for total pre-raid population at these different distances were
available. Such figures would be necessary in order to compute per cent
mortality. A calculation made by the British Mission to Japan and based on
a preliminary analysis of the study of the Joint Medical-Atomic Bomb
Investigating Commission gives the following calculated values for per cent
mortality at increasing distances from X:

TABLE C
Per-Cent Mortality at Various Distances

Distance from X, Per-cent Mortality
in feet
0 - 1000 93.0%
1000 - 2000 92.0
2000 - 3000 86.0
3000 - 4000 69.0
4000 - 5000 49.0
5000 - 6000 31.5
6000 - 7000 12.5
7000 - 8000 1.3
8000 - 9000 0.5
9000 - 10,000 0.0

It seems almost certain from the various reports that the greatest total
number of deaths were those occurring immediately after the bombing. The
causes of many of the deaths can only be surmised, and of course many
persons near the center of explosion suffered fatal injuries from more than
one of the bomb effects. The proper order of importance for possible
causes of death is: burns, mechanical injury, and gamma radiation. Early
estimates by the Japanese are shown in D below:

TABLE D
Cause of Immediate Deaths

City Cause of Death Per-cent of Total
Hiroshima Burns 60%
Falling debris 30
Other 10

Nagasaki Burns 95%
Falling debris 9
Flying glass 7
Other 7