Invade or Bomb?
By May of 1945 an exhausted and overrun Germany had surrendered. The war in Europe was over. The United States, aided by Great Britain, moved closer and closer to Japan. Massive suicide attacks by the Japanese caused great losses to the Pacific Fleet, but did not deter its drive.
Japan, thinking the Soviet Union was a friendly neutral in the war in the Pacific, submitted unofficial peace feelers to the United States through them. The Soviet Union, secretly wanting to join the war against Japan, suppressed the feelers. Ironically, the Japanese military made it impossible to pursue peace directly, as they arrested or killed anybody who tried to extend official peace offerings. As it was, these unofficial feelers were completely unacceptable to the U.S. as they merely made vague offering to return conquered territories in exchange for peace.
The big strategic question was how to force Japan's surrender.
Japan's major cities had been fire-bombed almost nightly. The islands were blockaded and the Japanese Navy had been destroyed. Planning for a massive invasion by Allied forces was underway. But was that the best answer? The cost in lives for both Allied forces and Japanese civilians would be heavy.
Harry S. Truman had just become the U.S. Presidency following Franklin Roosevelt's death. The United States wanted the Soviet Union to enter the war, but was concerned that it would dominate too much of East Asia if the war dragged on. There were two atomic bombs available. Truman made a quick decision: drop both bombs as soon as possible, allowing a short time between missions for Japanese surrender.