
Did the Soviet invasion of Manchuria matter more than the atomic bombs?
There’s a growing argument online that the atomic bombs did not really end WWII in the Pacific, and that Japan surrendered mainly because the Soviet Union entered the war and invaded Manchuria.
I think the reality is more complicated.
The Soviet declaration of war on Japan on August 8, 1945, was enormously important. Japan had been hoping that the USSR could mediate a negotiated peace. Once the Soviets invaded Manchuria, that diplomatic strategy collapsed. The rapid destruction of the Kwantung Army also demonstrated that Japan could potentially face a war against both the US and USSR.
But saying that the atomic bombs were irrelevant goes too far. Hiroshima shocked the Japanese leadership, and the destruction of two cities by nuclear weapons clearly became part of the crisis that led to surrender.
The timeline is particularly interesting:
August 6: Hiroshima
August 8: Soviet declaration of war
August 9: Soviet invasion of Manchuria + Nagasaki
August 10: Japan formally signals willingness to accept the Potsdam Declaration, with conditions
August 14: Hirohito makes the final decision
August 15: Japan announces surrender
So perhaps the better question isn't “Was it the atomic bomb or the Soviet invasion?”
It may be:
How did the atomic bombs and Soviet intervention affect different parts of Japan's strategic calculations, and which one mattered more in the final decision to surrender?
Personally, I think the Soviet intervention is seriously underrated in popular Western narratives, but “the atomic bombs had nothing to do with it” is just as simplistic as “the atomic bombs single-handedly ended the war.”
What do historians here think? Which factor was more decisive?