The campaign began with Japanese landings and occupation of several areas in the British Solomon Islands and Bougainville Island, in the Territory of New Guinea, during the first six months of 1942.

The Japanese occupied these islands and began the construction of several naval and air bases with the goals of protecting the flank of the Japanese offensive in New Guinea, establishing a security barrier for the major Japanese base at Rabaul on New Britain, and providing bases for interdicting supply lines.

[1][2] These islands were part of the Australian Territory of New Guinea, a League of Nations mandate since 1920.

Anchoring its defensive positions in the South Pacific was the major Japanese army and navy base at Rabaul, New Britain, which had been captured from the Australians in January 1942.

In March and April, Japanese forces occupied and began constructing an airfield at Buka Island in northern Bougainville, as well as an airfield and naval base at Buin, in southern Bougainville.