There’s evidence that humans settled on Bougainville at least 28,000 years ago.
Spanish mariner Luis Vaez de Torres passed through in 1606, and Bougainville acquired its name from French explorer Captain Louis-Antoine de Bougainville, who sailed up the east coast in 1768.
European settlements were established as the German New Guinea Company began trading in the late 1890s. Bougainville and Buka were considered part of the Solomons group, a British possession, until 1898 when they were traded to Germany. Australia seized the North Solomons, with the rest of New Guinea, at the start of WWI.
The Japanese arrived in 1942, swiftly defeating the Australians and holding most of the island until the end of the war. Buka became an important air base, and Buin, at the southern tip of Bougainville, was a base for ground troops. In 1943 American troops captured the port of Torokina and Australian forces fought their way south towards Buin. Of 80,000 Japanese troops only 23,000 were taken prisoner; 20,000 are thought to have been killed in action and the remaining 37,000 died of disease and starvation in the jungles. There’s a moving monument to the Japanese dead atop Sohano Island’s cliff.
In the 1960s and early 1970s, the North Solomons began a push to break away from Australian colonial control, climaxing in land disputes over the proposed Panguna mine. Before PNG independence, Bougainville pushed for an independent grouping of the Bismarck Archipelago. In 1974 the secessionist movement sprang into the picture.