Rabaul, the peacetime capital of the Australian Mandated Territory of New Guinea, fell to the Japanese on 23 January 1942. The small Australian garrison, Lark Force, was overwhelmed and most of its troops, including six army nurses, captured. Approximately 400 of the troops escaped to the mainland and another 160 were massacred at Tol Plantation. In July 1942, about 1000 of the captured Australian men, including civilian internees, were drowned when the Japanese transport ship Montevideo Maru was sunk by an American submarine off the Philippines coast en route to Hainan. Only the officers and nurses, sent to Japan on a different ship, survived.
The 2/22nd Battalion (about 900 men and 38 officers) formed the bulk of Lark Force. It had arrived in Rabaul on Anzac Day 1941. By December, Lark Force had increased to about 1400 troops. They included a headquarters group; part of the 2/10th Field Ambulance with 6 members of the Australian Army Nursing Service (AANS); anti-tank and coastal artillery batteries; and a number of militia in the New Guinea Volunteer Rifles, some of whom were only eighteen years old. Ten Wirraways and four Hudsons from 24 Squadron joined them just as Japan attacked Pearl Harbor and Malaya. In addition, approximately 150 men and officers of the 1st Independent Company were based on nearby New Ireland.
The troops had not been trained for service in the tropics. Although they had trained for longer in Australia than most battalions, they had trained for mobile warfare in open country. Five days after the Japanese entered the war in the Pacific, the Australian Chiefs of Staff had to advise the War Cabinet whether to reinforce, withdraw or leave the troops in Rabaul. Despite the Australian government's awareness that they would not be able to hold out against a strong Japanese force, they decided to leave the troops in place, removing only European women and children from the Territories.
The Japanese dropped their first bombs on Rabaul on 4 January 1942 and continued with almost daily air raids until the 5000-strong Japanese invasion force attacked Rabaul soon after midnight on 23 January 1942. Japanese ships entered the harbour and Japanese troops were landed at Blanche Bay. Lark Force had only a few anti-tank guns, mortars and Vickers machine-guns. The fighting was over in just a few hours and the Lark Force commander, Colonel Scanlan, ordered the men to disperse in an 'every man for himself' withdrawal. Men from 24 Squadron, whose Wirraways had been decimated in an earlier aerial battle, had a prearranged escape and airlift organised. The Army had no such escape plans for its troops. Only the fittest, most determined and luckiest survived the long withdrawal across New Britain.
The Japanese captured Rabaul with the loss of only 16 men. By May 1942, they had established themselves in the arc of islands north and east of Papua New Guinea and had seized the main coastal centres of Lae, Salamaua and Madang on the north coast of the mainland.