I love the argument that “Japan didn’t surrender because of the Bomb - they surrendered because the Soviets had just declared war and invaded Manchuria.” ??? Did the Soviets have the capability to mount an amphibious invasion of the home islands? Or the long-range bomber capability to do what our B-29’s had done? Or the Bomb? No, no, and no.
Richard B. Frank’s “DOWNFALL: The End of the Imperial Japanese Empire” concludes the same. The Japanese were most concerned with their home islands, and as word spread of nuclear attacks on Hiroshima and Nagasaki, and probability of more cities being heavily damaged or destroyed by American nuclear attack, panic and complete societal breakdown was inevitable. That is why Japan surrendered.