Main article: Debate over the atomic bombings of Hiroshima and Nagasaki
The role of the bombings in Japan's surrender, and the ethical, legal, and military controversies surrounding the United States' justification for them have been the subject of scholarly and popular debate.[320] On one hand, it has been argued that the bombings caused the Japanese surrender, thereby preventing casualties that an invasion of Japan would have involved.[7][321] Stimson talked of saving one million casualties.[322] The naval blockade might have starved the Japanese into submission without an invasion, but this would also have resulted in many more Japanese deaths.[323]
However, some critics of the bombings have cited a belief that atomic weapons are fundamentally immoral, that the bombings were war crimes, and that they constituted state terrorism.[324] Others, such as Japanese historian Tsuyoshi Hasegawa, argued that the entry of the Soviet Union into the war against Japan "played a much greater role than the atomic bombs in inducing Japan to surrender because it dashed any hope that Japan could terminate the war through Moscow's mediation".[325] A view among critics of the bombings, that was popularized by American historian Gar Alperovitz in 1965, is the idea of atomic diplomacy: that the United States used nuclear weapons to intimidate the Soviet Union in the early stages of the Cold War. James Orr wrote that this idea became the accepted position in Japan and that it may have played some part in the decision making of the US government.[326]