Japanese occupation began in mid 1942, when they defeated the Australians and held the island for most of the war. Buka was an important air base, Shortland was a major Naval base and Buin on the Southern tip of Bougainville was a important troop base.

Long term occupation plans included resettling Japanese civilians to the island's, "Little Tokyo" settlement. Americans landed in November of 1943 and captured western coast, with Australians fighting southward towards Buin. Of the 80,000 Japanese troops, only 23,000 survived to be taken prisoner. About 20,000 were KIA and 37,000 died in the jungle from disease and starvation.