Am I supposed to be intimidated or insulted because of your "retarded" comment? I learned a long time ago that insults only hurt when they hit the target's Achilles heel, and being called "retarded" isn't mine.
I've read about the Manhattan Project, the Potsdam Conference and the decision to drop the bomb, and it wasn't all cut-and-dried; there was a lot of posturing on Truman's part because he wanted to present a facade of American superiority to Stalin, and the bomb was his ace in the hole.
The Japanese were involved in surrender negotiations for months before the bombing and the Allies rejected their terms. However, it was just a matter of time as Japanese citizens were starving and starting to rebel against continued warfare.
Truman's 8/6/45 diary entry suggests more chest-beating than anything else.
7/25/45 Diary Entry:
"We met at 11 A.M. today. That is Stalin, Churchill and the U.S. President. But I had a most important session with Lord Mountbattan & General Marshall before than. We have discovered the most terrible bomb in the history of the world. It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark.
"Anyway we 'think' we have found the way to cause a disintegration of the atom. An experiment in the New Mexican desert was startling - to put it mildly. Thirteen pounds of the explosive caused the complete disintegration of a steel tower 60 feet high, created a crater 6 feet deep and 1,200 feet in diameter, knocked over a steel tower 1/2 mile away and knocked men down 10,000 yards away. The explosion was visible for more than 200 miles and audible for 40 miles and more.
"The weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop this terrible bomb on the old capital or the new [Kyoto or Tokyo].
"He [Stimson] and I are in accord. The target will be a purely military one and we will issue a warning statement [known as the Potsdam Proclamation] asking the Japs to surrender and save lives. I'm sure they will not do that, but we will have given them the chance. It is certainly a good thing for the world that Hitler's crowd or Stalin's did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful."
[Privately, Truman later expressed misgivings about the mass killing of civilians in Hiroshima; see the "Didn't the Japanese Deserve It?" section in Random Ramblings on Hiroshima.]
8/6/45: Excerpt from public statement by President Truman. This was the first time he publicly gave a reason for using the atomic bomb on Japan:
"The Japanese began the war from the air at Pearl Harbor. They have been repaid many fold.
"If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth." (Public Papers of the Presidents, Harry S. Truman, 1945, pg. 197, 199).
http://www.cfo.doe.gov/me70/manhattan/index.htm
http://www.doug-long.com/hst.htm