Bougainville island. Early History, First European Contact, German Period, World War II, Civil War, People and Culture, Island Information. Bougainville's close contact with the outside world and its integration into Papua New Guinea are recent. The first permanent Christian mission and first colonial administrative post (under German New Guinea) were established in 1901 and 1905 respectively. Relations were often troubled between Bougainville and central colonial authorities (German New Guinea to 1914, Australian-administered New Guinea from 1914 to 1946, with an interlude of Japanese Army control from 1942 to 1945, and Australian-administered Territory of Papua and New Guinea from 1946 to 1975). Bougainville attempted to secede only days before Papua New Guinea's independence