1945 Soviet invasion of the Japanese-owned Kuril Islands
Source (Wikipedia): Invasion of the Kuril Islands

The Invasion of the Kuril Islands was the World War II Soviet military operation to capture the Kuril Islands from Japan in 1945. The invasion, part of the Soviet–Japanese War, was decided on when plans to land on Hokkaido were abandoned. The successful military operations of the Red Army at Mutanchiang and during the invasion of South Sakhalin created the necessary prerequisites for invasion of the Kuril Islands.