3. The Military Effectiveness of the Atomic Bomb By A. K. Solomon Research Fellow in Physics and Chemistry, Harvard University Physicist at Los Alamos Laboratory of Manhattan District This report has been prepared in an attempt to set out, in a dispassionate manner, a summary of the published information on the destruction caused by the atomic bomb. In order to control the weapon adequately, it is first necessary to be aware of its potential power. The primary difficulty that confronts anyone who attempts to make an objective comparison between the atomic bomb and more conventional weapons is the paucity of the experimental evidence. Three bombs have been exploded. Of these the first, in New Mexico, was alone well instrumented. The next two were dropped against enemy targets, so that it was not possible to get adequate measures of the forces. Nonetheless certain primary effects stand out, differences from conventional bombing so large in amount that they become differences in kind. 1 3 The casualty figures are most striking. If one averages General Groves' figures for Hiroshima and Nagasaki, one finds an average of 68,000 people killed and 90,000 injured per bomb.2 Dr. L. L. Terry of the U.S. Strategic Bombing Survey has made one estimate comparing the results of incendiary bombing against Japan with those of the atomic bomb. He postulated a situation in which a sufficient number of incendiary bombs had been dropped to burn an area equal to that burned by the atomic bomb. In this case, "comparing mortality and morbidity figures we found that the figure for injuries would be 15.2 times as great by atomic bombing as by incendiary bombing." The contribution to the casualty rate of the only uniquely destructive feature of the bomb, its gamma radiation, is not large. Colonel Stafford L. Warren has estimated that with no gamma radiation the 2 4 1See Appendix II for a Who's Who of the authorities mentioned in this report. Hearings: Senate Atomic Energy Committee, Part 1, Nov. 28, 1945, page 32 ff. Ibid: Part 5, Feb. 15, 1946, page 514 ff. 'Ibid: Part 5, Feb. 15, 1916, page 508 ff. total casualties would have been 5 to 7 percent less. On the ground in Hiroshima and Nagasaki not enough radioactivity was deposited to cause any radiation damage after the initial explosion. Saturation and unpreparedness combined in Hiroshima to make the total effect much greater than it might otherwise have been. Thus, Dr. Philip Morrison says, "Of 300 registered physicians, more than 260 were unable to aid the injured. Of 2,400 nurses, orderlies, and trained first aid workers, more than 1,800 were made casualties in a single instant. It was the same everywhere." The general dislocation is expressed in a different way by Colonel Warren who stated, "We tried to get information from the Japanese survivors as to where they were at the time, so that we could set down precise figures as to the survival rates and mortalities and injuries and so on. It was almost impossible to get this information with any accuracy. We not infrequently found that the Japanese could not tell us where they were at the time within 1,000 meters." One tragic result of the magnitude of the calamity is illustrated in a passage from a Hiroshima eyewitness account published by Father J. A. Siemes, a German Jesuit missionary. "Thousands of wounded who died later could doubtless have been rescued had they received proper treatment and care, but rescue work in a catastrophe of this magnitude had not been envisioned; since the whole city had been knocked out at a blow, everything which had been prepared for emergency work was lost, and no preparation had been made for rescue work in the outlying districts." Blast, fire, and radiation are the three physical forces by which the bomb does its work. The relative effect of each of these can be adjusted by changes in the height of the bomb explosion; it also depends on details of the terrain and target over which the explosion takes place, and other local conditions. Thus at Hiroshima conditions were most favorable for the spread of fire, which therefore contributed in large measure to the total damage. At both Hiroshima and Nagasaki, great damage was done by blast. The Japanese surrender, which so closely followed the use of the atomic bomb, made it possible for experts to examine and measure Hiroshima and Nagasaki shortly after their destruction. Numerous expert teams were sent into the area, some from the Manhattan District and some from the United States Strategic Bombing Survey. There is some disagreement in the available evidence about the quantitative results of the bombing, but none about the qualitative results. A tabular summary of the published results is presented in Appendix I, along with casualty estimates and other pertinent Ibid: Part 2, Dec. 6, 1945, page 233 ff. * Saturday Review of Literature, vol. 29, May 11, 1946, page 24 ff. (reprinted). comments. Most of these figures are taken from the U. S. Senate Atomic Energy Committee Hearings, where a great deal of the evidence was submitted in what might be called "10 ton blockbuster equivalents"—a convenient and picturesque unit. A ten ton blockbuster contains about 5 tons of TNT. The stated energy equivalent of the atomic bomb is 20,000 tons of TNT. However, one is not justified in expecting the destruction caused by the atomic bomb to increase by so great a factor; it has long been known that the blast damage goes up only as a fractional power of the energy released. The most conservative and best reasoned figures are those given by Dr. H. L. Bowman, director of the Physical Damage Division of the United States Strategic Bombing Survey. Taking an average of his figures for multi-story brick and multi-story steel or concrete buildings, we obtain a figure of 167 for the effectiveness of the atomic bomb expressed in 10 ton blockbuster units. 3 Further extrapolation would-imply that the diminishing returns in blast damage make it uneconomic to build much larger bombs than those dropped on the Japanese cities. However, another effect comes in; the area of fire damage resulting from the intense heat generated by the bomb is essentially proportional to the energy released by the bomb. Thus the economic factor is no longer dominant, and the limit to bomb size becomes in the end a technological one alone. In this connection it is useful to recall that the atomic bomb has already a considerable economic advantage over the conventional bomb. Professor J. R. Oppenheimer has stated that "it is somewhere between 10 and 100 times cheaper to deliver atomic weapons. . . in terms of the area destroyed". 7 3 Expressed in units of absolute destruction, the bomb at Hiroshima produced, General Farrell testified, 4 square miles of absolute destruction, and 3 more of serious damage, making a total of 7. The corresponding figures at Nagasaki, where the built up area was less, were 2.4 and 1.2, making a total of 3.6. At Hiroshima reinforced concrete buildings were rendered one third useless up to 2,000 ft. from the center, brick multi-story buildings were destroyed up to 5,700 ft., and one-story buildings were completely destroyed up to 7,700 ft. At Nagasaki concrete buildings with 6 to 10 inch walls were destroyed up to 2,000 ft., churches with 18 inch brick walls at 3.500 ft.; there was partial damage to 9 inch brick walls at 5,000 ft. Windows were destroyed out to 12,000 ft. Hiroshima and Nagasaki were towns of relatively flimsy construction and it has been suggested that the relative effectiveness of T Ibid: Part 5, Feb. 15, 1946, page 514 ff. Hearings: Senate Atomic Energy Committee, Part 2, Dec. 5, 1945, page 195. Ibid: Part 5, Feb. 15, 1946, page 502 ff. the two bombs would differ in stronger cities. However, Paul H. Nitze, Vice-Chairman of the U. S. Strategic Bombing Survey," stated that "the stronger weapon is relatively just as effective against strong structures as it is against weak structures." Further evidence presented showed that the Nagasaki bomb, a more modern weapon, was more effective than the Hiroshima one,3 particularly as regards blast. Another major effect is fire, arising not only from the great heat generated by the atomic bomb but also from subsidiary effects such as short circuits, over-turned chimneys, or other fractures attendant upon the main blast. No direct figures exist giving the amount of fire damage; it is virtually impossible to disentangle the various causes of the vast destruction. Dr. Philip Morrison has stated, "When the bomb is detonated in the middle of a city, it is as though a small piece of the sun has been instantly created." 6 5 Terror, as a weapon against morale, cannot be discounted. In Hiroshima, a city totally unprepared for a bomb of this magnitude, fear was dominant. For example, immediately after the bomb fell, each civilian thought that it had exploded in his immediate neighborhood. Father Siemes states, "The magnitude of the disaster that befell Hiroshima was only slowly pieced together in my mind. I lived through the catastrophe, and saw it only in flashes, which only gradually were merged to give me a total picture." Another witness, a Japanese staff officer, put it more succinctly, for he said, "All this from one bomb; it is unendurable." Terror as a weapon probably has diminishing returns. As the danger becomes familiar, terror subsides, to be replaced by the continued psychological strain attendant upon bombing. How long the strain can be endured, it is impossible to predict; the Germans in Berlin were not broken by Allied bombing. In other words, pure terror of the unknown as a weapon against morale is most effective in the initial stages of the attack. Of course, this argument would be important only if the initial attack were not itself critical and overpowering. The power of the bomb has thus been amply attested. Its use against an alerted population with a higher state of industrial organization and efficiency will produce effects difficult to assess in advance. Saturation on cities such as London, Paris, Berlin, and New York is more difficult to achieve, and a people well disciplined and organized, housed in adequate shelters designed to withstand such a bomb, will be able to recuperate faster and to combat much more efficiently those secondary effects which took such a high toll 2 Ibid: Part 5, Feb. 15, 1946, page 514 ff. Ibid: Part 2, Dec. 6, 1945, page 233 ff. Saturday Review of Literature, vol. 29, May 11, 1946, page 24 ff. (reprinted). in Hiroshima. The primary effects of the explosion cannot of course be controlled. Despite the tremendous cost in civilian casualty and destruction, war with this weapon will not be completely unendurable in a country adequately prepared and strong enough to withstand the first onslaught. The length of the war would certainly be increased by adequate dispersion of great industrial areas and the construction of subterranean factories. In the future, as in the past, we can expect war to continue until so much destruction takes place that the will to resist is finally broken. But we cannot forget that present, and indeed future, defense against airborne missiles is not, nor is ever likely to be, 100 percent effective. Nations must face the danger of an enemy who strikes so suddenly and effectively that defenses are paralyzed and the battle lost before the power to resist has been mobilized. |