>Russia did not invade Japan.
The Russian invasion of and the colaspe of the Japanese army Manchuria had a very large effect on moving Japan towards surender. However, it was our nuking of Japan that triggered the Russian invasion as they to grab wanted some of the Japanese held land before Japan surrendered in the face endless nuke attacks.
I thought at Tehran and Yalta Russia's assistance in fighting Japan had been secured?
No doubt a combination of the atomic bombing of Hiroshima and Nagasaki, in addition to the conventional bombing raids, combined with Russia's declaration played a very significant role in Japan's decision to surrender.