All your points are well taken, Turnbull, but as I said before, I don't think we actually know for certain why Japan surrended. Even today, the evidence is somewhat contradictory, and historians still disagree. For example, Richard Frank in "Downfall" stresses the important of the bombs, while Tsuyoshi Hasegawa, in his book "Racing the Enemy," argues that the Soviet intervention was decisive by itself without the bombs. One of the biggest problems in answering "was it the bombs, the Soviets, or both" is that both developments happend virtually simultaneously.