My father turned draft age in the fall of ‘45. If no atomic bombs, I’d rate his chances of having been killed in an invasion of Japan at approx. 50-50. My existence is as likely as not owed to Truman, Oppenheimer et al.
My Dad was a non-combatant (ordnance supply and maintenance) in New Guinea and the Philippines. Even so, he might not have survived an invasion of Japan.
My dad was drafted into the navy and was at basic training at Seneca Lake in upstate New York when they dropped the bombs. He was drafted after Germany surrendered so he was heading for the invasion of Japan. He did spend a year after the war in the Aleutian Islands to relive a troop stationed there.