The only way anyone can judge Truman’s motives in dropping the atomic bomb is by analyzing the result of his decision. No one can know, even by reading his personal diary, the exact reasons he had for using the bomb. It was likely a combination of many: punishment, justification of cost, saving lives, and ending the war as quickly as possible. However, it is evident that in the “grand scheme of things” the use of the atomic bomb saved lives. About 105,000 Japanese lost their lives in Hiroshima and Nagasaki. While this is a high number, the number who died in the American bombing raids on the six largest Japanese cities is far greater, about 250,000. Consequently, such a large number of deaths is by no means unprecedented. An invasion of Japan would possibly have cost between 250,000 and three million Japanese and American lives and ended the war four months later, at the very earliest. It may be concluded that no more people died in the atomic bombings than would have in an invasion of Kyushu, and that said bombings did have the effect of ending the war more quickly. Truman’s motives, therefore, cannot be called into question in light of the results of his decision.
At least in this case, the end justifies the means.