I am of the opinion that the very first nuke, let alone the second one, was grossly unnecessary and that the incidents account for the single-most despicable act of WWII. The only remotely favorable plea that could be made in my view is that of gross ignorance, as apparently there were plans to use nuclear weapons to clear beaches before friendly forces moved in.
I shall use [link]http://www.doug-long.com/[/link] as a source and shall be doing a cut and paste job of sections. The bold is for emphasis. Underlined sentences are my own opinions.
And so from November 1944 onward, Japan was the subject of numerous large-scale B-29 non-nuclear bombing raids (Robert Butow, Japan's Decision To Surrender, pg. 41). When Air Force chief General Hap Arnold asked in June 1945 when the war was going to end, the commander of the B-29 raids, General Curtis LeMay, told him September or October 1945, because by then they would have run out of industrial targets to bomb (Sherry, pg. 300 & 410(143n))
On August 6, 1945, an atomic bomb was dropped on the people of Hiroshima.
The proclamation demanded "the unconditional surrender of all the Japanese armed forces" (U.S. Dept. of State, Foreign Relations of the U.S., The Conference of Berlin (Potsdam), vol. 2, pg. 1474-1476). It made no mention of Japan's central surrender consideration: the retention of the Emperor's position (Butow, pg. 138-139). What made this crucial was that the Japanese believed their Emperor to be a god, the heart of the Japanese people and culture (Pacific War Research Society, Japan's Longest Day, pg. 20). The absence of any assurance regarding the Emperor's fate became Japan's chief objection to the Potsdam Proclamation (Pacific War Research Society, The Day Man Lost, pg. 212-214). In addition, the proclamation made statements that, to the Japanese, could appear threatening to the Emperor.
Early in the morning of
August 9th (
How convenient...) Manchuria was invaded by the Soviet Union. The Soviets had notified Japan's Ambassador to Moscow
on the night of the eighth (
Gee thanks for the notice bud!) that the Soviet Union would be at war with Japan as of
August 9th (Butow, pg. 153-154, 164

). This was a blow to the Japanese government's peace-seeking efforts. The Russians had been the only major nation with which Japan
still had a neutrality pact, and, as such, (had been
Japan's main hope of negotiating a peace with something better than unconditional surrender terms (Butow, pg. 87). To that end, the Japanese government
had been pursuing Soviet mediation (
I guess the Japanese peace diplomats were looking at the Russians funny...) to end the war in response to the Emperor's request of
June 22, 1945, a fact often overlooked today. (Butow, pg. 118-120, 130)
Late on the morning of
August 9th, the U.S. dropped a second atomic bomb without a second thought, this time on the people of Nagasaki.
Bringing the nuclear threat closer to home, rumors were reported to the Japanese military that the next atomic bomb would be dropped on Tokyo, where the government leaders were meeting (William Craig, The Fall of Japan, pg. 116).
Bombed by the Allies at will, Japan was militarily defeated. It still remained, however, for defeat to be translated into surrender
The Emperor's Desire On the following day,
August 14, Anami, Umezu, and Toyoda were still arguing that there was a chance for victory (John Toland, The Rising Sun, pg. 936). But then that same day, the Cabinet unanimously agreed to surrender (Toland, pg. 939).
Where none of the previous events had succeeded in bringing the Japanese military leaders to surrender,
surrender came at Emperor Hirohito's request: "It is my desire that you, my Ministers of State, accede to my wishes and forthwith accept the Allied reply" (Butow, pg. 207-208)
Surrender was so repugnant to Anami that he committed hara-kiri the day after he signed the surrender document (Butow, pg. 219-220).
Where fear and reason had failed, religious devotion to the Emperor enabled the military leaders to overcome their samurai resistance to surrender.
July 1945 - Japan's peace messages Still, the messages from Togo to Sato, read by the U.S. at the time, clearly indicated that Japan was seeking to end the war:
President Truman knew of the messages' content
In passing up this possible opportunity for an earlier and less deadly peace, Truman was not deliberately trying to prolong the war so the atomic bomb could be used on Japan to intimidate the Soviets. Briefly stated, it is likely that Truman believed the use of atomic bombs on Japan was necessary primarily for the reasons he always gave: "We have used it in order to shorten the agony of war, in order to save the lives of thousands and thousands of young Americans"
A point made by then Assistant Sec. of War John McCloy and seconded by the then Deputy Director of the Office of Naval Intelligence, Captain Ellis Zacharias (http://www.doug-long.com/quotes.htm#Zach) is of particular importance. Regarding the decision to drop atomic bombs on Japan, McCloy later wrote,
"everyone was so intent on winning the war by military means that the introduction of political considerations was almost accidental" (John McCloy, The Challenge to American Foreign Policy, pg. 42, my emphasis). Zacharias lamented,
"while Allied leaders were immediately inclined to support all innovations however bold and novel in the strictly military sphere, they frowned upon similar innovations in the sphere of diplomatic and psychological warfare" (Ellis Zacharias, The A-Bomb Was Not Needed, United Nations World, Aug. 1949, pg. 29). Defeating Japan was perceived of by the Allies in the narrow terms of military methods. The Japanese messages intercepted by the U.S. in July showed the Japanese government's view toward the war had changed. However, the U.S. didn't keep up with this change, and the advantage of combining diplomatic methods with military methods was largely missed.
The Japanese government correctly interpreted this and other statements in the Allied surrender terms to mean that the Emperor could be retained. On August 14 the Emperor told Japan's cabinet, "I have studied the Allied reply and concluded that it virtually acknowledges the position of our note [requesting the Emperor's retention] sent a few days ago. I find it quite acceptable." (Toland, pg. 936-937). With this reassurance and at the Emperor's "desire", on August 14 the Japanese Cabinet unanimously signed the surrender document, agreeing to Allied terms (Toland, pg. 939).
Although the Japanese military still wished to fight on as late as August 14, it was the doves rather than the hawks in Japan's government who had the final say. As mentioned earlier, it was the atomic bomb plus the belief that the Emperor might be retained that finally led the doves to play their trump card: the direct intervention of the Emperor requesting the Cabinet to surrender immediately.