Karafuto Prefecture
From the signing of the 1875 Treaty of Saint Petersburg until the Russo-Japanese War which broke in 1904, Russia had full control of Sakhalin island. As a result of the 1905 Treaty of Portsmouth that brought an end to the Russo-Japanese War, the portion of the island south of the 50th parallel line became Japanese territory, part of Karafuto Prefecture. However, following the month long Soviet–Japanese War during the summer of 1945, the entire island was reunified under Soviet control.