RE: whether the atomic bombs were necessary (or prudent) in ending the Pacific War:
Japan had been putting out feelers for surrender from as soon as November of 1944 which were simply ignored; Roosevelt and Truman would settle for nothing less than 'unconditional surrender' and were entirely unwilling even pretend to negotiate. Ironically, the only condition the Japanese were serious about - maintaining the Emperor and the Imperial system - was accepted after the 'unconditional' surrender. How many hundreds of thousands of people died unnecessarily for those two little letters, I wonder?
The atomic bombs were a consideration in the decision for unconditional surrender, the Japanese were familiar with the atomic bomb concept and figured - correctly - that the United States couldn't have very many more of them after the first two were dropped (I think there was one more ready to go in 1945, the rest wouldn't've been ready until 1946). The Soviet invasion of Manchuria was seen as a far more serious development. Hirohito was also upset that the defensive preparations in the Home Islands were entirely inadequate, and the Army had been lying to him about it.
Forcing the unconditional surrender of Japan was a huge strategic blunder; occupying and demilitarizing an industrialized, capitalist, and western-friendly country (remember, Japan had been allied with England until the 1930's - and several of the older battleships the US Navy sunk during the war had "Made in England" stamped on them) that had proven itself very militarily capable eliminated the only real challenge to communist domination in East Asia. I can't help but wonder how long Communism would've lasted if China hadn't gone "Red" - something that could've been prevented with either an earlier peace in China, or if Chiang Kai-Shek would've accepted Japanese help against the communists after the Japanese surrender (it may not've been too far-fetched - Chiang had to be kidnapped by his own generals to force him to sign a cease-fire with the Chinese Communists when the Japanese invaded - although if Japan had never invaded China in the first place, Chiang Kai-Shek probably would've obliterated the communists on his own in the late 30s/early 40s). It is difficult to imagine an aggressive communist block surrounded on one side by the combined might of the industrialized Western powers and on the other by China's (and to a lesser extent Japan's) bottomless manpower pool(s).
The only good thing to come out of the unconditional surrender of Japan was the War Crimes trials, but even then there were a lot of mistakes made, a lot of guilty people let free, and - like the Nuremberg Trials - it was largely "Victors' Justice" done by people with much higher body counts than the people they were trying. (one book I've read argued that many people who committed the worst atrocities were let go in exchange for telling the allies where they'd stashed all the gold and other valuables the Japanese had looted from east Asia during the war).