[user104658]

The reason that the a bomb ended the war was because it was a demonstration of the firepower that was available. It would probably have had the same effect if they had dropped the nukes on unpopulated areas. Either way, what it was was a "warning shot", and one that worked. "Let's end this now - because we have THESE".

The reason specific civilian targets were chosen was because the US wanted to prove that they weren't bluffing, and had "the balls" to straight up wipe the country off the map. To scare them into surrender. In other words, it was an act of terrorism, and certainly a war crime.

But then, every country involved in WW2 was involved in or complacent in war crimes by the end of the war... It was a very messy war. What happened happened. However, I do think it's hugely disrespectful to describe what happened to the innocent people of those two cities as anything but a tragedy. You can do that without going into whose "fault" it all was.