one topic not discussed much but applicable here were the firebombing campaigns. total civilian deaths from those far outweighed even the two a-bomb attacks. General Curtis Lemay, the general behind the firebombing campaigns had this to say:
"Killing Japanese didn't bother me very much at that time... I suppose if I had lost the war, I would have been tried as a war criminal. "
Not that the japanese military carried itself any better during its own conventional bombing campaign in china, but this doesn't negate the fact that usually civilian deaths are supposed to be minimized in a war, unless you are the aggressor, and that those who directly target them and lose are usually tried for war crimes post war.