In July of 1945 the United States was mired in war. Germany had surrendered, but Japan was still a dangerous threat. The military was developing plans to invade. But the invasion was expected to be the most costly operation in the history of the country’s military. Casualty estimates ranged from half a million to a million American troops. (ref) For comparison’s sake, the American Civil War, which spanned from 1861 to 1865 and was costliest war in US history, cost a total of over 600,000 soldiers between both sides.(ref) In addition to American troops, Many more Japanese soldiers and civilians would have been killed. President Truman had fought in World War I and had firsthand knowledge of the horrors of war.
In Japanese culture, honor was everything. People reacted to dishonor by disemboweling themselves.(ref) The air force had developed squadrons of pilots who each had the goal of suicidally flying their airplanes into enemy ships. (ref)Because of the sense of duty and honor that is part of Japanese culture, there was little hope that the inevitable defeat would force a surrender.
But there was an alternative. In July, the government had tested a revolutionary weapon. In New Mexico they had detonated the world’s first atomic bomb – with the explosive force of between 15 and 20 kilotons.(ref) It was hoped that using this new weapon would force the quick surrender that a conventional invasion wouldn’t. In deciding whether to use the atomic bomb, resident Truman had to weigh the human costs of such use against the costs of continuing to fight a conventional war.
The biggest consideration was minimizing deaths – and, most-specifically, American deaths. As noted above, a traditional invasion would have likely cost over half a million American lives as well as many Japanese. The bomb that was dropped on Hiroshima killed an estimated 80,000 lives and the bombing of Nagasaki killed an estimated 45,000.(ref) Thus, the bombing actually saved lives in the final tally. What’s more, it saved American lives, which is a primary consideration for the American government.
The long-term effects of environmental impact of atomic weapons were not well understood. This is evidenced by the fact that the earliest tests of such weapons were carried out on American soil. It is widely accepted that American film icon, John Wayne, died of cancer brought about by radiation exposure experienced during the filming of The Conqueror in New Mexico near the sight of many early tests.(ref) To an extent, the military viewed atomic weapons simply as bigger bombs. This is evidenced by the fact that, post-World War II, the American military expected atomic weapons to be part of the normal process of warfare, and conducted exercises that involved soldiers crouching in trenches while a bomb was detonated and then charging toward the center of the blast. The death toll in Hiroshima was lower than the 100,000 killed in one night of conventional firebombing of Tokyo.(ref)
In today’s world, one of the major reasons that use of atomic weapons is generally considered off the table is the risk of a global conflagration that could destroy all of humanity. But that is a consequence of a global arsenal of nearly 15,000 bombs held by nine countries,(ref) some of which are thousands of times as powerful as the Hiroshima and Nagasaki bombs.(ref) At a time when the US was the only nation with such weapons, there was no risk of other countries responding in kind.
Given the considerations and the context, it seems that the decision to drop the atomic bomb on Hiroshima was a reasonable one.
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