Originally Posted by Missileer

I think this is closest to the truth.

"How could a president, or the others charged with responsibility for the decision, answer to the American people if... after the bloodbath of an invasion of Japan, it became known that a weapon sufficient to end the war had been available by midsummer and was not used?"

I think that the resistance that Japan had shown in the Pacific island hopping campaign demonstrated the futility hope for a Japanese surrender.