What role did the Soviet Union play in the victory over Japan?

Great Britain and the United States at the Yalta Conference said that they themselves would be able to defeat Japan. However, this will require several million soldiers and up to two years. The entry into the war of the USSR against Japan turned into a collapse for the latter. The most efficient and numerous Kwantung army, which was considered the last reserve of the Japanese emperor, was defeated. The army was supposed to be used to protect the islands from invasion – by ferrying from Korea to Japan. However, after the defeat from the USSR, resistance was useless.