We didn’t nuke Japan for fun

Well, a bit for fun. Eisenhower didn't want to nuke Nagoya because he spent his honeymoon there.

But you're right otherwise, the bombs were dropped because the USSR was making too much headway and preparing a naval invasion of the main island set for mere days after the bombs were dropped, which would have given them an edge at the negotiating table.

warned civilians by dropping pamphlets

Didn't seem to help much, their shadows are still singed against the pavement.