I have to assume this played a role in the decision not to do it. It's easy to see such an act leading to the extermination of the Japanese people.
I don't know about extermination, but the invasion of Japan would have gone in, to hell with the casualties, especially the Japanese ones!
Oh, believe me, I am, Ricky! The invasion of Japan would have been a bloodbath for both sides, especially the Japanese. Those who wish to say hateful things about America's dropping the A-bombs on Japan ridicule the idea that the USA would have suffered a million casualties in such an invasion; I, for one, still believe that such losses were possible. And even if the figure is too high, the actual casualty list would have been horrific.