I refuse to second guess Truman. A relative was onboard a ship headed for the Japanese invasion the same day the first bomb was dropped. His CO lined them up & said, “Look at the man on your right & on your left. Two out of the three of you will die in this invasion. Fight it like your life depends on it; because it does.” When they heard Truman had dropped the bomb; their ship turned around & they went back home. - My Daddy had fought the Germans in N. Africa, Sicily, Italy & at last in Germany. As a hardened combat veteran he would have been sent to Japan.
Japan started something they couldn’t finish. Their leadership should have counted the cost.
if they would have gotten pearl harbor with carriers present it may have turned out a lot different.