Since this is about history I'll feel that I'll have to contribute.
About the first atomic bombs. The first bomb, over Hiroshima, I can see how it was justifiable for the US government, it was a way to end the war against Japan quickly and they wouldn't have to invade mainland Japan at high costs in both lives and equipment. In retrospect though, seeing the suffering the radiation brought, doubt comes. But it is always easy to be critical when you have all the answers.
The second bomb, over Nagasaki, was not necessary. If the US had waited just a few days the Japanese would probably have surrendered without loss of either American or Japanese lives. But from what I've read the US government very much wanted to test the other bomb, being an H-bomb rather than a A-bomb, which can be seen in the fact that the target was fifth on a list based on target importance. The rest of the targets being disqualified due to weather or other circumstances.