Report of the British Mission to Japan
Chapter VII
CASUALTIES
79. The important causes of direct injury from the explosion, flashburn and gamma rays, have been described in the two preceding chapters. However, with the atomic as with other bombs, indirect injuries caused the death of a high proportion of the casualties, and probably of the bulk of them—except in so far as these were killed as it were several times over, by each lethal agent separately.
80. The greatest number of indirect injuries, and indeed of all deaths, appears to have been caused by the collapse of buildings. Photograph 19 shows the Japanese house as a light building, but it is not therefore to be despised as a lethal weapon, for its heavy roof timbers and tiling are inadequately supported (see paragraph 37) and must have killed or trapped thousands. Photograph 20 shows that injuries of the same kind were caused in the stronger buildings by the mass of wooden detail with which the Japanese embellished them, and which has been described in paragraph 68. Mechanical injuries resulting from people being thrown about, or from having arms or legs violently removed by flying debris, appear to have formed a lower proportion than in conventional attacks.
81. Fire in conventional air attack is rarely a major cause of casualties. There have been exceptions, among them the great incendiary raids on Hamburg and Tokyo, where the number of dead approached that in Hiroshima; but drawn from a much larger damage area. Very many people were, however, burnt to death in Hiroshima and Nagasaki, for there was almost no attempt to rescue those who were trapped or hemmed in by debris while points of fire sprang up round them. Bums received in the fires appear throughout the records of those admitted to hospital.
82. In Nagasaki but not in Hiroshima, a rumour was current which age has made almost respectable, for it appeared in the London Blitz and before that in Barcelona during the Spanish Civil War. This was that large numbers of people had been ripped open by the blast, and their entrails exposed; their eyes and tongues were said also to have hung out. Experience in this country has shown that blast pressure alone does not in fact cause these sensational effects on the human body. It was therefore not unexpected that two Nagasaki survivors who had spoken of seeing hundreds or thousands of such bodies on examination reduced their claim to one or two. Flying debris would be expected to produce a few such injuries. Cases of genuine injury from high blast pressures, such as ruptured ear-drums, were rare among survivors.
83. No conclusions can yet be reached regarding the relative importance of the different lethal agents. It is thought that those who died immediately were divided roughly equally between those killed by debris and those burnt, either by heat radiation or in the fires. Severe injuries from debris may extend to 2 miles, but are rare beyond1½ miles from the centre of damage. Beyond this distance gamma ray effects fall even more rapidly, and the major source of casualties is flashburn and fire.
84. Disasters as vast as those which befell Hiroshima and Nagasaki are difficult to fix in numbers. Most of the city records were destroyed, many public servants were killed, and in the chaos which followed little note was taken of the fate of individuals when the population was in mass flight. The Mission had to content itself with estimating from such records as were available that the number of people killed in Hiroshima lay between 70,000 and 90,000. Since then the Occupying Authority have published official figures for Hiroshima, of 78,150 dead, as well as 13,983 still missing. For comparison, the number of those killed by air attack during the whole war in London was 30,000, and the number of those killed throughout Great Britain, including London, was 60,000.
85. The number of those killed by a bomb depends on the number and whereabouts of those exposed to it. Therefore the number of dead is only a crude measure of the effects of the atomic bomb ; a better measure is given by the percentages of those at various distances from the explosion who died. It was possible to estimate these from comparatively good records which exist of the whereabouts in Hiroshima and of the subsequent fate of about 15,000 school-children. Few of these were actually in school when the bomb fell, for most were scattered through the city in groups doing a variety of war jobs ; so that it is believed that they form a representative sample of people going about their normal work in the city, some in the open, others in buildings giving varying protection. The Mission's interpretation of the records of the fate of these children is as follows :—
Distance from the centre of damage
Percentage of those within this zone who were killed
0 - ¼ mile
95 per cent.
¼ - ½ mile
85 per cent.
½ - ¾ mile
58 per cent.
¾ - 1 mile
35 per cent.
1 - 1½ miles
13 per cent.
1½ - 2 miles
½ per cent.
Experience in Great Britain has shown that in conventional raids children of school age are neither appreciably more nor appreciably less vulnerable to bombing than are adults. It is therefore reasonable to apply this table equally to adults.
86. It was possible to obtain the distribution of population in Nagasaki, where those in the Urakami valley exposed to the explosion numbered rather less than 100,000. On applying the table to this distribution, the resulting figure of dead is 37,000. This may be regarded as reasonable confirmation of the table ; for it is in fair agreement on the one hand with the estimate of 34,000 dead made by the Mission from Japanese population records, and on the other hand with the figure of 40,000 killed which is current among medical authorities. No official figures for Nagasaki have yet been published by the Occupying Authorities.
87. As the difference between the figures for Hiroshima and Nagasaki shows» the number of those killed depends rather obviously upon the number of those who were present. It is therefore customary in considering the effects of bombs to use a casualty rate from which inequalities in the distribution of population have been removed. For this purpose a standard density of population is assumed at about 45 to the acre, the density in the central London boroughs and the larger British cities. At this density the average effect of the Hiroshima and Nagasaki bombs is 65,000 killed. In British cities, the better protection afforded by the houses, their lower susceptibility to fire, and improved rescue services, would reduce this figure by an amount which can only be conjectured, but which is unlikely to exceed one-quarter. (This is equivalent to reducing all distances listed in the table by one-eighth.) The standard figure in British conditions would therefore be approximately 50,000 dead. The comparable standard figure for the German V2 rocket was about 15 dead.
88. The figure of 50,000 dead from one atomic bomb in average British urban conditions is probably the most important which this report contains. It shows that much the most serious effect of the atomic bomb is in producing casualties. The problem of providing against and of treating gamma ray casualties in particular is exceptionally grave and difficult.
CASUALTIES
79. The important causes of direct injury from the explosion, flashburn and gamma rays, have been described in the two preceding chapters. However, with the atomic as with other bombs, indirect injuries caused the death of a high proportion of the casualties, and probably of the bulk of them—except in so far as these were killed as it were several times over, by each lethal agent separately.
80. The greatest number of indirect injuries, and indeed of all deaths, appears to have been caused by the collapse of buildings. Photograph 19 shows the Japanese house as a light building, but it is not therefore to be despised as a lethal weapon, for its heavy roof timbers and tiling are inadequately supported (see paragraph 37) and must have killed or trapped thousands. Photograph 20 shows that injuries of the same kind were caused in the stronger buildings by the mass of wooden detail with which the Japanese embellished them, and which has been described in paragraph 68. Mechanical injuries resulting from people being thrown about, or from having arms or legs violently removed by flying debris, appear to have formed a lower proportion than in conventional attacks.
81. Fire in conventional air attack is rarely a major cause of casualties. There have been exceptions, among them the great incendiary raids on Hamburg and Tokyo, where the number of dead approached that in Hiroshima; but drawn from a much larger damage area. Very many people were, however, burnt to death in Hiroshima and Nagasaki, for there was almost no attempt to rescue those who were trapped or hemmed in by debris while points of fire sprang up round them. Bums received in the fires appear throughout the records of those admitted to hospital.
82. In Nagasaki but not in Hiroshima, a rumour was current which age has made almost respectable, for it appeared in the London Blitz and before that in Barcelona during the Spanish Civil War. This was that large numbers of people had been ripped open by the blast, and their entrails exposed; their eyes and tongues were said also to have hung out. Experience in this country has shown that blast pressure alone does not in fact cause these sensational effects on the human body. It was therefore not unexpected that two Nagasaki survivors who had spoken of seeing hundreds or thousands of such bodies on examination reduced their claim to one or two. Flying debris would be expected to produce a few such injuries. Cases of genuine injury from high blast pressures, such as ruptured ear-drums, were rare among survivors.
83. No conclusions can yet be reached regarding the relative importance of the different lethal agents. It is thought that those who died immediately were divided roughly equally between those killed by debris and those burnt, either by heat radiation or in the fires. Severe injuries from debris may extend to 2 miles, but are rare beyond1½ miles from the centre of damage. Beyond this distance gamma ray effects fall even more rapidly, and the major source of casualties is flashburn and fire.
84. Disasters as vast as those which befell Hiroshima and Nagasaki are difficult to fix in numbers. Most of the city records were destroyed, many public servants were killed, and in the chaos which followed little note was taken of the fate of individuals when the population was in mass flight. The Mission had to content itself with estimating from such records as were available that the number of people killed in Hiroshima lay between 70,000 and 90,000. Since then the Occupying Authority have published official figures for Hiroshima, of 78,150 dead, as well as 13,983 still missing. For comparison, the number of those killed by air attack during the whole war in London was 30,000, and the number of those killed throughout Great Britain, including London, was 60,000.
85. The number of those killed by a bomb depends on the number and whereabouts of those exposed to it. Therefore the number of dead is only a crude measure of the effects of the atomic bomb ; a better measure is given by the percentages of those at various distances from the explosion who died. It was possible to estimate these from comparatively good records which exist of the whereabouts in Hiroshima and of the subsequent fate of about 15,000 school-children. Few of these were actually in school when the bomb fell, for most were scattered through the city in groups doing a variety of war jobs ; so that it is believed that they form a representative sample of people going about their normal work in the city, some in the open, others in buildings giving varying protection. The Mission's interpretation of the records of the fate of these children is as follows :—
| Distance from the centre of damage | Percentage of those within this zone who were killed |
|---|---|
| 0 - ¼ mile | 95 per cent. |
| ¼ - ½ mile | 85 per cent. |
| ½ - ¾ mile | 58 per cent. |
| ¾ - 1 mile | 35 per cent. |
| 1 - 1½ miles | 13 per cent. |
| 1½ - 2 miles | ½ per cent. |
Experience in Great Britain has shown that in conventional raids children of school age are neither appreciably more nor appreciably less vulnerable to bombing than are adults. It is therefore reasonable to apply this table equally to adults.
86. It was possible to obtain the distribution of population in Nagasaki, where those in the Urakami valley exposed to the explosion numbered rather less than 100,000. On applying the table to this distribution, the resulting figure of dead is 37,000. This may be regarded as reasonable confirmation of the table ; for it is in fair agreement on the one hand with the estimate of 34,000 dead made by the Mission from Japanese population records, and on the other hand with the figure of 40,000 killed which is current among medical authorities. No official figures for Nagasaki have yet been published by the Occupying Authorities.
87. As the difference between the figures for Hiroshima and Nagasaki shows» the number of those killed depends rather obviously upon the number of those who were present. It is therefore customary in considering the effects of bombs to use a casualty rate from which inequalities in the distribution of population have been removed. For this purpose a standard density of population is assumed at about 45 to the acre, the density in the central London boroughs and the larger British cities. At this density the average effect of the Hiroshima and Nagasaki bombs is 65,000 killed. In British cities, the better protection afforded by the houses, their lower susceptibility to fire, and improved rescue services, would reduce this figure by an amount which can only be conjectured, but which is unlikely to exceed one-quarter. (This is equivalent to reducing all distances listed in the table by one-eighth.) The standard figure in British conditions would therefore be approximately 50,000 dead. The comparable standard figure for the German V2 rocket was about 15 dead.
88. The figure of 50,000 dead from one atomic bomb in average British urban conditions is probably the most important which this report contains. It shows that much the most serious effect of the atomic bomb is in producing casualties. The problem of providing against and of treating gamma ray casualties in particular is exceptionally grave and difficult.