What two reasons President Truman decided to use the atomic bomb on Japan?

Answer 1

Truman said at the time that it was the right thing to do, after first being informed of the existence of the Manhattan Project and carefully studying the question. He believed it would bring the war to an end, and obviate the necessity for the bloodbath everyone expected if an invasion of the Japanese Home Islands were necessary to end the war. There were still eight million Japanese troops in China who had never lost a battle, and every day that the war went on people were dying. He also understood that if he did not use the bomb, and instead ordered the invasion of Japan, and the US sustained the one million casulaties estimted for that operation, and then it was revealed that the US had spent a few billion 1940 dollars and successfully developed a weapon that might have won the war, and he ordered it NOT to be used, and instead went for a conventional invasion with its concomitant slaughter, that he would be lucky not to be lynched by the families of the men lost in that invasion.

Answer 2

1. Japan refused to surrender

2. Invading the Japanese mainland was projected to cost the lives of 1 million Allied soldiers.