More can be written, but you might like to start with the FAQ section "The atomic bombs, aka questions /u/restricteddata has answered". The one that's most immediately applicable is "Did the US *have* to nuke Japan in WWII?" by /u/restricteddata. There are several other good discussions in there that go into details, like the timeline of Japan's surrender, or the reasons for the surrender (the nuclear bombings? the Soviet invasion? both? neither? other?).

This is not to discourage discussion. More questions, data and debate are welcome.