The Soviet Union invaded Manchuria in August 1945 during the final phase of World War II.
The Soviet offensive began on August 9, 1945, against Japanese-held Manchuria and the Japanese puppet state of Manchukuo. Soviet forces attacked from several directions, rapidly overwhelming the Kwantung Army, Japan’s major military force in the region.
The timing was significant. The invasion came three days after the atomic bombing of Hiroshima and on the same date as the bombing of Nagasaki. Japan’s leaders had hoped the Soviet Union might mediate with the Western Allies, so the Soviet declaration of war removed an important diplomatic possibility.
The invasion, the atomic bombings, and Japan’s worsening military position all shaped the surrender decision. Fighting continued in some areas after the August 15 announcement, and the Japanese Instrument of Surrender was not signed until September 2.