A question I have always wondered, is why didn't they surrender after the first bomb?
Then again why did they so quickly surrender after the second? Did they really think we had the ability or the will to nuke the entire island? I heard we had maybe one more oporational weapon and then would have taken months before we could make more.
They didn't surrender right after Hiroshima because they didn't know quite what had happened to the city, only that something American destroyed it. Truman announced the attack sixteen hours later, I don't know if the Japanese believed what he said. Somewhere in this time frame (it may have been after Nagasaki) a captured American pilot told them told them we had hundreds of bombs just like it.
Probably the factor that really forced the surrender was the fact that the bombs knocked Hirohito's head out of his butt, and he recognized that he was cult leader not a God. His decision to end the war, and actions to bring that about were THE factor in the Japanese surrender. It's worth noting what he said in the Imperial Rescript announcing the decision " the war situation has developed not necessarily to Japan's advantage, while the general trends of the world have all turned against her interest." Understatement to say the least, but it illustrates the Japanese viewpoint at the time. Incidently, he read the speech in an anachronistic court Japanese, most of his subjects had no idea what he was saying. They also had never heard his voice before.