Comment by estearum

"Needed to win the war," no. The US could've continued to firebomb and then follow with a land invasion, which would've killed both more Japanese and more Allies.

Was it the best path to end the war? Certainly.

The modern argument around targeting civilians or not was not even relevant at the time due to the advent of strategic bombing, which itself was seen as less-horrific than the stalemated trench warfare of WW1. The question was only whether to target civilian inputs to the military with an atomic weapon (and hopefully shock & awe into submission) or firebomb and invade.