jelly, look at the quotes - leading American generals and historians:
In a 1986 study, historian and journalist Edwin P. Hoyt nailed the "great myth, perpetuated by well-meaning people throughout the world," that "the atomic bomb caused the surrender of Japan." In Japan's War: The Great Pacific Conflict (p. 420), he explained:
The fact is that as far as the Japanese militarists were concerned, the atomic bomb was just another weapon. The two atomic bombs at Hiroshima and Nagasaki were icing on the cake, and did not do as much damage as the firebombings of Japanese cities. The B-29 firebombing campaign had brought the destruction of 3,100,000 homes, leaving 15 million people homeless, and killing about a million of them. It was the ruthless firebombing, and Hirohito's realization that if necessary the Allies would completely destroy Japan and kill every Japanese to achieve "unconditional surrender" that persuaded him to the decision to end the war. The atomic bomb is indeed a fearsome weapon, but it was not the cause of Japan's surrender, even though the myth persists even to this day.
In a trenchant new book, The Decision to Drop the Atomic Bomb (Praeger, 1996), historian Dennis D. Wainstock concludes that the bombings were not only unnecessary, but were based on a vengeful policy that actually harmed American interests. He writes (pp. 124, 132):
... By April 1945, Japan's leaders realized that the war was lost. Their main stumbling block to surrender was the United States' insistence on unconditional surrender. They specifically needed to know whether the United States would allow Hirohito to remain on the throne. They feared that the United States would depose him, try him as a war criminal, or even execute him ...
Unconditional surrender was a policy of revenge, and it hurt America's national self-interest. It prolonged the war in both Europe and East Asia, and it helped to expand Soviet power in those areas.
General Douglas MacArthur, Commander of US Army forces in the Pacific, stated on numerous occasions before his death that the atomic bomb was completely unnecessary from a military point of view: "My staff was unanimous in believing that Japan was on the point of collapse and surrender."
General Curtis LeMay, who had pioneered precision bombing of Germany and Japan (and who later headed the Strategic Air Command and served as Air Force chief of staff), put it most succinctly: "The atomic bomb had nothing to do with the end of the war."