There was a study conducted by the United States Navy in April of 1945, in which the Chief of Naval Operations Staff had determined that a continued naval and air blockade of Japan would result in the complete disintegration of Japan's war-making capability and civilian governance by mid-1946, at latest.
However, this study ran afoul of one particular that it could never quite enumerate to anyone's satisfaction: what effect would continued kamikaze attacks have upon the Pacific Fleet and, and what would they mean in terms of casualties? Those questions could not be answered, but it was assumed that eventually, the Japanese would run out of planes and pilots, and that at (then)current rates of attrition, both would run out relatively soon.
The Japanese merchant fleet was (mostly) on the bottom, ensuring that Japan, a country with no native raw materials of signifigance, would see it's war industries cease operations for lack of materials. The effects of the relentless unrestricted submarine warfare, mining of Japanese ports, air and naval blockade of Japanese home waters, were already having a telling effect. By the time of the invasion of Okinawa, Japan had little more than 6 months of oil reserves left with which to carry on the war.
Japan was cripppled. The sticking point, in terms of surrender, had nothing to do with continuing the fight for the sake of it; it had everything to do with the ridiculous notions of Unconditional Surrender put forth at Potsdam. One of the main bullet points of the Potsdam Declaration was that the head of state and the head of government would be tried for War Crimes (in this case, conspiring to engage in destructive war). In the case of Japan, the head of state andhead of government are the same person; Emperor Hirohito.
In the case of the Germans, the head of state and government was the same person (Admiral Doenitz, by the end of the war). Germany did not worship Doenitz, nor was Doenitz necessary to the reconstruction of the country. To the Japanese, this was Emperor Hirohito, and this would be like putting God on trial. There could BE no Japan without Hirohito, unlike a Germany without Doenitz, and he was sacred. So they continued to fight.
It was this refusal to bend on the sanctity of the Emperor that caused the fight to continue, and necessitated the atomic bombings of Japan. After the Japanese surrender, Hirohito was not tried in a court of law over anything, was he? So, was there an unconditional surrender at all? Hardly.
Japan kept it's emperor.
The purpose behind Unconditional Surrender and adherance to Potsdam was purely political; it was intended to keep a tenuous (at best) allied alliance together long enough to "win" the war. In Japan's attempt to wriggle free of Potsdam, the Japanese Prime Minister, Shigematsu (who had replaced Tojo near the end) specifically warned the Allies in public that if they did not drop the requirement to bow to Potsdam, the Japanese would begin the slaughter of 400,000 allied POW's (both military and civilian) in Japanese custody. This, incidentally, occured two days before the official surrender of Japan.
Obviously, the Emperor was not tried for war crimes, no ,mass execution of Allied POWs occurred in the very last days of the war. Potsdam didn't mean a thing. Without it, the rationale for both Japanese beligerence and Allied atomic bombings, is non-existant.