New Britain had been Japanese territory since February 1942, when Imperial forces overwhelmed the small Australian garrison at Rabaul and turned the town into the most formidable base in the Southwest Pacific. US forces had landed at Cape Gloucester and Arawe in December 1943 as part of MacArthur's Operation Cartwheel, and by August 1944 the Americans had pushed east as far as Talasea and Cape Hoskins. Then the US 40th Infantry Division took over, and the war on New Britain settled into what Australian official historian Gavin Long called a "tacit truce" - the Americans guarding their airfields, the Japanese sitting tight. In November 1944, that quiet inheritance passed to the Australian 5th Division under Major General Alan Ramsay, whose men were told to start pushing east.

The 14th/32nd Infantry Battalion came ashore at Jacquinot Bay on the southern coast in November 1944. There was no opposition. Over the following weeks the Australian 6th Infantry Brigade under Brigadier Raymond Sandover built up a base of operations there, while the 36th Infantry Battalion took over from the Americans at Cape Hoskins on the northern coast. The 13th Infantry Brigade arrived to defend Jacquinot Bay. Brigadier Cedric Edgar's 4th Infantry Brigade began landing elements. Aircraft from the Royal Australian Air Force and the Royal New Zealand Air Force bombed Japanese positions around Rabaul, and the Japanese - with only a handful of serviceable aircraft left - made no attempt to intercept. The stage was set for a slow, deliberate advance across the island's waist, the Australians hoping to reach and hold a line before the Japanese could concentrate against them.

Between late January and early February 1945, the 6th Brigade pushed eastward along the southern coast toward Milim and Henry Reid Bay. Boomerang fighters and Beaufort fighter-bombers attacked Japanese positions around Karlai Plantation on 15 February, and the 14th/32nd took the position the same day after the defenders withdrew under artillery fire. Two days later the same battalion took the trading station at Kamandram. Working north from Henry Reid Bay, the Australians crossed the Wulwut River with engineer support and began a grinding six-week fight against fortified Japanese positions on Mount Sugi. The ridges above the Waitavalo and Tol plantations were defended with pillboxes, mortars, and machine guns. Heavy tropical rain turned the jeep tracks below into seas of mud. The bridge over the Mevelo River washed away. Japanese aircraft appeared for the first and only time in the campaign in mid-March, dropping bombs on the bridge over the Wulwut and causing casualties among the men below. On 18 March, the 14th/32nd took Bacon Hill, the most significant action of the six-week fight.

By April 1945 the Australians had their line. From Wide Bay on the south to Open Bay on the north, they had sealed off the narrow waist of New Britain and caged the 93,000 Japanese soldiers around Rabaul on the Gazelle Peninsula. What followed was not battle but patrol - small groups moving through dense jungle to maintain the initiative and watch the line. For the rest of the war, the Australian advance essentially stopped. The Japanese commander, under orders from Tokyo to preserve his strength for a future joint action with the Imperial Japanese Navy that never came, chose not to counter-attack. Australian casualties for the entire campaign were 53 killed, 140 wounded, and 21 more dead from other causes. Japanese dead, as recorded by Australian sources, numbered at least 206. The war ended in August 1945 with the garrison still intact, the line still held.

One of the Japanese soldiers caught in this quiet siege was Shigeru Mizuki, who would later become one of Japan's most celebrated cartoonists. Mizuki survived New Britain - he lost an arm in an Allied air raid - and spent much of his postwar career turning the experience into comics and memoir. His works Onward Towards Our Noble Deaths and Showa: A History of Japan tell the story of the Pacific War from the perspective of the ordinary conscripts who were expected to die for an empire that had effectively abandoned them. The Battle of Wide Bay-Open Bay rarely makes the first draft of Second World War histories. It has no Iwo Jima, no Okinawa, no symbolic capture of a capital. But as a case study in how to win without fighting - how to neutralize an enemy twenty times your own size through geography, air power, and patience - it remains what Australian military historians have called a classic containment campaign.