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 24,700
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