It's my understand the United States only had one nuclear weapon left when the Japanese surrendered. This last nuclear weapon (a Fat Man type?) was at Moffett Field awaiting shipment east when the Emperor signaled Japan's surrender. Along this line, I had an interesting chat with a Moffett Field locksmith. He was clearing out old security safes (classified document containers) to be surplused when he found a blueprint stuffed behind one of the drawers. It turns out this blueprint was for the bomb rack of one of the nuclear bombs used against the Japanese.

People do ignore the fact that the Japanese did not surrender immediately after Hiroshima. They also ignore the fact that the Emperor had to personally intervene to bring about surrender. There were fanatics within the Japanese government who wanted to physically stop the Emperor from issuing the surrender decree (they thought national suicide was more honorable). Several fanatics committed suicide in front of the empirial residence in Tokyo to protest the surrender. There is no doubt the use of nuclear weapons saved hundreds of thousands of American and Japanese lives. However there remains the ethical question of whether or not the United States should have developed thermonuclear weapons. Unlike nuclear fission, controlled nuclear fusion is a completely different technology from thermonuclear weapons (uncontrolled nuclear fusion). IMHO we should have frozen nuclear weapons technology at nuclear fission and not proceeded to nuclear fusion.

Gary