That's not quite accurate. The Allies demanded unconditional surrender at Potsdam. The Japanese refused because they wanted to ensure that the Emperor remained on the throne (amongst other conditions, many of which were also unacceptable to the Allies). After the bombs and the Soviet declaration of war, the Japanese agreed to the unconditional surrender. The decision to allow the Emperor to remain was made by the Allies after the surrender, it was not part of the surrender agreement. The Japanese did indeed change their minds about unconditional surrender between July 27th and August 15th. The fact that the Allies later decided it was in everyone's best interests to keep the Imperial system intact does not change the fact that Japan did not agree to unconditional surrender prior to the bombs and the Soviet invasion, and did agree to it afterwards.
Bookmarks