I do disagree. The Japanese were hoping to seek favourable terms for surrender after the Potsdam Declaration in Jun 45 and the first bomb on Hiroshima. The brokers for those favourable terms were hoped to be the Soviets, whom had been neutral with Japan since a pact in 1941. When the Soviets invaded on the same day of the Nagasaki bomb, the hopes for those favourable terms were totally lost. What we will never know is whether the Soviet invasion would have changed that surrender - if the Japanese had surrendered in the hours between the Soviet invasion and the second bomb, we would have done. Unfortunately, the story is very convenient to anti nuclear weapon believers on the theory of deterrence of Mutually Assured Destruction. I believe the Soviet invasion was just another stressor, on top of the naval blockade “Operation STARVATION” and the fire bombings. The coupe de grace was indeed the 2x Bombs that delivered on the Potsdam Declaration. The rest is history...