The Battle of North Borneo took place during the Second World War between Allied and Japanese forces. Part of the wider Borneo campaign of the Pacific War, it was fought between 10 June and 15 August 1945 in North Borneo. The battle involved a series of amphibious landings by Australian forces on various points on the mainland around Brunei Bay and upon islands situated around the bay. Japanese opposition to the landings was sporadic initially, although as the campaign progressed a number of considerable clashes occurred and both sides suffered significant casualties, although major combat was largely restricted to Labuan and around Beaufort. On the mainland, while Allied conventional operations focused largely on the coastal areas around Brunei Bay, guerrilla forces consisting of Dayak tribesmen and small numbers of Allied personnel from the Services Reconnaissance Department fought an unconventional campaign in the interior. The Allies were successful in seizing control of the region. Nevertheless, many of the strategic gains that possession of North Borneo provided were ultimately negated by the sudden conclusion of the war in August 1945.

The 9th Division was a division of the Australian Army that served during World War II. It was the fourth division raised for the Second Australian Imperial Force. The distinctions of the division include it being:in front line combat longer, cumulatively, than any other Australian division; one of the Australian military's most decorated formations; the only 2nd AIF division formed in the United Kingdom, from infantry brigades and support units formed in Australia; praised by both Allied and Axis generals, including Bernard Montgomery and Erwin Rommel, as well as non-Australian military historians, and; like the 6th and 7th Divisions, being one of only a few Allied army units to serve in both the Mediterranean and Pacific theatres.