WWII? The atom bombs on Japan? I tried to understand the history, causes, read the Richard Rhodes books, other books, watched documentaries and movies, etc.
As I read this thread, I guess that it has more and better thinking about the issues of morality, ethics, various steps that could have been attempted with Japan, atomic weapons stopping wars, etc. than Truman considered when he decided to drop the bombs and conclude that Truman saw just two cases: (1) Drop atomic bombs, end the war within not many hours, and save lives of US soldiers. (2) Delay, attempt, look for alternatives and possibilities, negotiate, demonstrate, ..., and lose more US lives. So, he picked (1), and maybe he did it in less than 10 minutes.
Saving American lives was probably the dominant factor, but Americans expected that a land invasion would also kill millions of Japanese, far more than the atomic bombs.
There are strong indications that a surrender would occur regardless and why would the only alternative to a land invasion of Japan be dropping two nuclear bombs on Japanese cities.
They didn't surrender after the first, and the military leadership didn't want to surrender after the second (the emperor did anyway and there was an attempted coup).
Note that more people were killed by firebombing Tokyo than either nuke, Japan was completely at the mercy of US bombing raids before the atomic bombs and they still refused to surrender.
As I read this thread, I guess that it has more and better thinking about the issues of morality, ethics, various steps that could have been attempted with Japan, atomic weapons stopping wars, etc. than Truman considered when he decided to drop the bombs and conclude that Truman saw just two cases: (1) Drop atomic bombs, end the war within not many hours, and save lives of US soldiers. (2) Delay, attempt, look for alternatives and possibilities, negotiate, demonstrate, ..., and lose more US lives. So, he picked (1), and maybe he did it in less than 10 minutes.