Let me say this. I consider Truman one of the worst human beings for his dropping atomic bombs on largely civilian populations
The alternatives were:
*Blockade Japan until they starved into submission. Millions of Japanese citizens die as the war continues.
*Invade Japan. Millions of Allied and possibly tens of millions of Japanese soldiers and civilians die.
Or accept the Japanese conditions for surrender which had been offered since late 1944 (i.e. guaranteeing that the Emperor would not lose his throne).