The struggle for New Guinea began with the capture by the Japanese of the city of Rabaul at the northeastern tip of New Britain Island in January 1942 (the Allies responded with multiple bombing raids, of which the action off Bougainville was one). Rabaul overlooks Simpson Harbor, a considerable natural anchorage, and was ideal for the construction of airfields. Over the next year, the Japanese built up the area into a major air and naval base.