[geoschmo]

Of course this can be written off as self-justification, but the use of the two bombs may have indeed helped humanity in the long run. The history of man has been a long series of bloody conrfontations with progressivly more efficent technology developed to destroy each other. Once we used the two we had, the temporary lack of additional devices, and the war ending gave us time to consider them and gain perspective about their use. Later conflicts have all had the spectre of nuclear holocaust hanging over us, but we have figured out a way to avoid using them.

One could come up with a very plausible alternate history in which the US did not use the bomb on Japan. The war of course would have still ended, perhaps a little later, perhaps a lot. The cold war would have still likely occured, but perhaps without the perspective given by Hiroshima and Nagasaki, there would have been less hesitance to use them. In this case it wouldn't have been a nuclear power using two bombs against a non-nuclear power. Once the first one was used, the other side would have the incentive to retaliate, and means to do so. Instead of two cities nuked at the end of a war, it might have been 20, or 200 before it was all over.