@Olivier5,
Had Japan not surrendered and we progressed to invasion, the American casualties from the invasion were projected to equal all the casualties that we had sustained in WWII up to that point. So if Japan had kept refusing to surrender, Hiroshima and Nagasaki would have marked the halfway point of the war.
In fact, we still have Purple Heart medals minted in expectation of the invasion of Japan left to hand out to wounded soldiers. All of the casualties of the Korean and Vietnam Wars combined were not enough to exhaust the stockpile that we had built up just to deal with the invasion of Japan.
Olivier5 wrote:And the targets were not military. The point was to kill as many civilians as possible.
That is incorrect. There was no intent to harm civilians.
Hiroshima was a huge military center with tens of thousands of Japanese soldiers. Hiroshima Castle was the military headquarters in charge of repelling any invasion in the southern half of Japan.
The second A-bomb was meant for Kokura Arsenal, a massive (1250 meters by 610 meters) arms production complex. Due to wartime difficulties they were not able to strike that target and ended up dropping the bomb on an industrial zone north of Nagasaki, directly between the Mitsubishi Steel and Arms Works and the Mitsubishi Ordnance Works.
Before WWII, Pearl Harbor had been regarded as immune to air-dropped torpedoes because the water was so shallow that they would embed themselves into the mud. Japan had to invent special torpedoes in order to attack Pearl Harbor, and the Mitsubishi Ordnance Works was the place that designed and built those torpedoes.
The damage to the torpedo factory was most satisfactory.
http://web.archive.org/web/20060929120212/cfo.doe.gov/me70/manhattan/nagasaki.htm