The first Japanese settlers came across from Hokkaido in the early 1800s, attracted by marine life so rich that one explorer wrote 'the water looked as though it was boiling'. The island already had occupants in the form of the Nivkhi, Oroki and Ainu peoples but, just as this didn't give pause to the Japanese, the Russians were equally heedless when they claimed Sakhalin in 1853. Japan agreed to recognise Russian sovereignty in exchange for the rights to the Kuril Islands.
In 1882 the tsar made the remote island into one huge penal colony. Anton Chekhov visited in 1890, resulting in his A Journey to Sakhalin, in which he wrote: 'I have seen Ceylon which is paradise and Sakhalin which is hell.' (Though he said Sakhalin's experiences influenced all his writing thereafter.)
Japan restaked its claim, seizing the island during the Russo-Japanese War and getting to keep the southern half, which they called Karafuto, under the terms of the Treaty of Portsmouth, 1905. In the final days of WWII, though, the Soviet Union staged a successful invasion of the island. Sakhalin became a highly militarised eastern outpost of the Soviet empire, loaded with aircraft, missiles and guns. Just how sensitive Sakhalin had become was illustrated in 1983, when the off-course Korean Airlines flight 007 was shot down by the Russians. All 267 on board were killed.