Why did truman decide to use the atomic bomb against japan? do you think he did the right thing?

He used the atomic bomb against Japan because they were one of the world's major powers. They quickly industrialized and imperalized countries bigger than their own but USA didn't have that kind of firepower but we had bombs to drop with huge explosive power and Japan wasn't ready for that. Think to yourself and say what if Japan imperalized my country were or who would I be now