The Battle of Rabaul, also known by the Japanese as Operation R, an instigating action of the New Guinea campaign, was fought on the island of New Britain in the Australian Territory of New Guinea, from 23 January into February 1942. It was a strategically significant defeat of Allied forces by Japan in the Pacific campaign of World War II, with the Japanese invasion force quickly overwhelming the small Australian garrison, the majority of which was either killed or captured. Hostilities on the neighbouring island of New Ireland are usually considered to be part of the same battle. Rabaul was significant because of its proximity to the Japanese territory of the Caroline Islands, site of a major Imperial Japanese Navy base on Truk.
Following the capture of the port of Rabaul, Japanese forces turned it into a major base and proceeded to land on mainland New Guinea, advancing toward Port Moresby. Heavy fighting followed along the Kokoda Track, and around Milne Bay, before the Japanese were eventually pushed back towards Buna–Gona by early 1943. As part of Operation Cartwheel, throughout 1943–1945, Allied forces later sought to isolate the Japanese garrison on Rabaul, rather than capturing it, largely using air power to do so, with US and Australian ground forces pursuing a limited campaign in western New Britain during this time.
By the end of the war, there was still a sizeable garrison at Rabaul, with large quantities of equipment that were subsequently abandoned. In the aftermath, it took the Allies over two years to repatriate the captured Japanese soldiers, while clean up efforts continued past the late 1950s. Many relics including ships, aircraft and weapons, as well as abandoned positions and tunnels, remain in the area.
Prelude
Rabaul lies on the eastern end of the island of New Britain. At the time of the battle, the town was the capital of the Australian-administered Territory of New Guinea, having been captured from the Germans in 1914. In March 1941, the Australians dispatched a small garrison to the region, as tensions with Japan heightened. The small Australian Army garrison in New Britain was built around Lieutenant Colonel Howard Carr's 700-strong 2/22nd Battalion, an Australian Imperial Force (AIF) infantry battalion. This battalion formed part of Lark Force, which eventually numbered 1,400 men and was commanded by Lieutenant Colonel John Scanlan. The force also included personnel from a local Militia unit, the New Guinea Volunteer Rifles (NGVR), a coastal defence battery, an anti-aircraft battery, an anti-tank battery and a detachment of the 2/10th Field Ambulance. The 2/22nd Battalion Band—which was also included in Lark Force—is perhaps the only military unit ever to have been entirely recruited from the ranks of the Salvation Army. A commando unit, the 130-strong 2/1st Independent Company, was detached to garrison the nearby island of New Ireland.
thumb|left|upright=1.5|Map depicting eastern New Guinea and New Britain
Throughout 1941, the Allies had planned to build Rabaul up as a "secure fleet anchorage" with plans to establish a radar station and a strong defensive minefield; however, these plans were ultimately shelved. Allied planners later determined that they did not have the capacity to expand the garrison around Rabaul, nor was the naval situation conducive to reinforcing it should the garrison come under attack. Nevertheless, the decision was made that the garrison would remain in place to hold Rabaul as a forward observation post. The main tasks of the garrison were protection of Vunakanau, the main Royal Australian Air Force (RAAF) airfield near Rabaul, and the nearby flying boat anchorage in Simpson Harbour, which were important for the surveillance of Japanese movements in the region. However, the RAAF contingent, under Wing Commander John Lerew, had little offensive capability with only 10 lightly armed CAC Wirraway training aircraft and four Lockheed Hudson light bombers from No. 24 Squadron.
For the Japanese, Rabaul was important because of its proximity to the Caroline Islands, which was the site of a major Imperial Japanese Navy base on Truk. The capture of New Britain offered them a deep water harbour and airfields to provide protection to Truk and also to interdict Allied lines of communication between the United States and Australia. Following the capture of Guam, the South Seas Detachment, under Major General Tomitaro Horii, was tasked with capturing Kavieng and Rabaul As a result of the intense air attacks, Australian coastal artillery was destroyed, and Australian infantry withdrew from Rabaul. The following day, an RAAF Catalina flying boat crew located the invasion fleet off Kavieng, and its crew managed to send a signal before being shot down. At least 800 soldiers and 200 civilian prisoners of war—most of them Australian—lost their lives on 1 July 1942, when the ship on which they were being transported from Rabaul to Japan, the Montevideo Maru, was sunk off the north coast of Luzon by the U.S. submarine .
Subsequent operations
According to Japanese author Kengoro Tanaka, the operation to capture Rabaul was the only operation of the New Guinea campaign that was completely successful for the Japanese. Following the capture of Rabaul, the Japanese quickly repaired the damage to Rabaul's airfield, and Rabaul became the largest Japanese base in New Guinea and the linchpin to their defences in the region. The Australians tried to restrict Rabaul's development soon after its capture by a bombing counter-attack in March.