Soviet forces invaded Manchuria on August 9, 1945, as Japan faced surrender. The region was then largely controlled by Japan through the puppet state of Manchukuo.
The Soviet Union declared war on Japan late on August 8 and began its offensive shortly after midnight on August 9. Soviet forces attacked from several directions, overwhelming the Japanese Kwantung Army, one of Japan’s largest military forces.
The invasion had major political importance because Japanese leaders had hoped the Soviet Union might mediate between Japan and the Western Allies. Soviet entry destroyed that diplomatic hope and opened another front against Japan’s remaining empire.
The invasion occurred between the atomic bombings of Hiroshima and Nagasaki. Historians continue to debate the relative weight of the atomic attacks and Soviet intervention in Japan’s decision to surrender, but both developments were central to the final days of the Pacific War.