The Japanese had been trying to surrender since January, the only condition they were asking was that the Emperor be spared. The lie on that was that the Russians wouldn't send the offers on because they wanted to get in on vivisecting Japan. This was proven wrong only recently. The Russians sent the offers and Truman ignored them. Truman wanted to drop the bomb so as to show the Russians we had it and what it could do. Even after the Bomb many Generals wanted to fight on, only the entry of Russia ended even their opposition. After the surrender the Emperor volunteered to be executed if it would spare other Japanese. MacArthur let him go, though we had a version of Nuremberg there too