[fch42]

fair enough to notice though that while the Soviet Union may have had agreed to enter the war with Japan (at the Potsdam conference ?), it had not done so by the time the nuclear bomb on Hiroshima was dropped. It did declare war on Japan the day before the Nagasaki bombing. In a way ... Stalin chose the "let's go to war with Japan" date opportunistically. When it was clear there could be much gain without too much pain.

Which is not a dissimilar thing to the US "wavering" over the commitment to an invasion of Japan. The nuclear bombs "resolved" that. We'll never know what would have happened otherwise.