[actionfromafar]

Isn't there a decent argument nowadays that the nuclear bombs didn't even matter that much to Japan military command?

That it was the threat of Soviet invasion which really tipped the scales.

[vkou]

> That it was the threat of Soviet invasion which really tipped the scales.

That's exactly what tipped the scales. The Soviet betrayal of the non-aggression pact, their march through the Inner Mongolia desert (Which Japanese planners considered impossible, given the lack of logistics infrastructure in it), their blitz through Manchuria, the complete collapse of Japan's positions in it, as well as the Soviet naval invasion of the Sakhalin and Kuril islands was what brought the war to a close. Japan could not continue the war without access to Manchuria, and was really, really not interested in getting occupied by the Soviets.

[philwelch]

People always claim this, but it doesn't make very much sense to me. The Soviets did invade Manchuria I think the same day as the Nagasaki bombing, but a full invasion even of occupied China, let alone the home islands, would have been logistically challenging for them, and the Japanese would have known this. It would require sending and supplying troops through Siberia, which even today has limited infrastructure. They possibly could have used Western transport ships to stage their forces somewhere in the Pacific, but those transports would have already been full of American and British troops being staged in the theater for the same purpose.

At any rate, Japan prior to the atomic bombings had two reasons to surrender: the blockade and impending starvation of the Japanese people and the risk of an American invasion of the home islands. The Soviet invasion of Manchuria and the atomic bombings represented two more reasons. The entire weight of circumstances forced Japan to surrender when it did; I think it's very hard to deny that the atomic bombs were not a necessary aspect of that.