Japan's decision to surrender was made before the scale of the Soviet attack on Manchuria, Sakhalin, and the Kuril Islands was known (See Downfall, pg 289),

Operation August Storm, along with the two atomic bombings on Hiroshima and Nagasaki, combined to break the Japanese political deadlock and force Japan's surrender; they made it clear that Japan had no hope of holding out, even in the Home Islands.

Tsuyoshi Hasegawa's research has led him to conclude that the atomic bombings themselves were not the principal reason for capitulation. Instead, he contends, it was the swift and devastating Soviet victories on the mainland in the week following Stalin's August 8 declaration of war that forced the Japanese message of surrender on August 15, 1945.