In the final days of WWII and immediately after, Soviet forces invaded and occupied the Japanese-held southern half of Sakhalin Island and the Kuril Island chain, formally annexing them in 1945–46. Almost the entire Japanese civilian population, along with the small indigenous Ainu community, was expelled or repatriated to Japan by 1949, while ethnic Koreans who had been brought to the islands as forced laborers were largely denied Soviet or Japanese citizenship for years afterward. The USSR (and later Russia) has administered the territory since, while Japan has never recognized the loss of the four southernmost Kuril islands. No peace treaty formally ending the state of war between Japan and Russia has been signed, and the sovereignty dispute remains unresolved.
Soviet Union invaded and annexed Japanese-administered South Sakhalin (Karafuto) and the Kuril Islands, expelling most Japanese and Ainu residents
The Japanese census of 1941 counted about 406,000 people in Karafuto, with roughly 17,000 in the Kurils; wartime movement leaves the August 1945 figure near 400,000-420,000. It included Ainu and Nivkh communities and some 23,000-43,000 Koreans brought as wartime labour, most of whom were not included in the repatriation to Japan and remained stateless on Sakhalin.
Japanese-derived accounts of the August 1945 campaign put civilian casualties in Karafuto at 3,500-3,700, of which roughly 1,000 died under naval and machine-gun fire at Maoka and more than 2,400 drowned when Soviet submarines sank the evacuation ships Ogasawara Maru and Taito Maru in Aniva Gulf. The figure excludes Japanese and Soviet military dead and excludes later mortality among Japanese POWs interned in the USSR, for which no agreed Sakhalin-specific figure exists.
Japanese repatriate testimony and postwar Japanese accounts, summarised in the standard histories of the Maoka landing, record Soviet forces firing on civilians in European-style dress and on refugee shipping.
Russia, Japan