[cocodill]

I believe it was the Soviet Union's entry into the war and quick breakthrough that forced the Japanese to quickly surrender on favorable terms.

[littlestymaar]

But that belief is unfortunately not more verifiable than the one that assumes it's the atomic bomb that did it.

We cannot categorically rule out any of the three hypothesis:

- the Manchuria invasion was sufficient

- the nuclear bombing was sufficient

- they were both necessary for the immediate surrender of Japan