Soviet forces invaded Japanese-held Manchuria immediately after the August 1945 declaration of war.
The invasion began shortly after midnight on August 9, 1945, following the Soviet declaration delivered late on August 8. The main target was the Japanese-controlled state of Manchukuo in Manchuria, where the Kwantung Army was stationed.
The Soviet campaign, known as the Soviet-Japanese War, also extended into Korea, South Sakhalin, and the Kuril Islands. Its rapid advance destroyed the Japanese Army's position in northeast Asia and contributed to the pressure that produced Japan's surrender.
Manchuria is sometimes confused with Korea or Sakhalin because Soviet operations reached those areas during the same campaign. The opening invasion, however, is specifically associated with Japanese-held Manchuria and the destruction of the Kwantung Army.