日ソ中立条約
After breaking the Soviet–Japanese Neutrality Pact, the Soviet Union invaded Karafuto and the Kuril Islands on August 11, 1945, just four days before the surrender of Japan. Although the Red Army outnumbered the Japanese 88th Division by three to one, it was unable to advance until additional reinforcements arrived on 16 August due to strong Japanese resistance. Actual fighting continued until August 21, and the capital of Toyohara fell on August 25.