The 2/22nd Battalion—composed of 716 men—made up the majority of the combat personnel in the Lark Force, the name given to the 1,400-strong garrison concentrated in Rabaul, New Britain, from March 1941. Lark Force also included personnel from the New Guinea Volunteer Rifles, a coastal defence battery, an anti-aircraft battery, an anti-tank battery and a detachment of the 2/10th Field Ambulance. The island, part of the Australian territory of New Guinea was important because of its proximity to the Japanese territory of the Caroline Islands, including a major Japanese Navy base on Truk Island. The main tasks of Lark Force were protection of the Royal Australian Air Force (RAAF) airfield and flying boat anchorage, which were important in the surveillance of Japanese movements in the region. A 130-strong detachment from the 2/1st Independent Company was detached to the nearby island of New Ireland.