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 (later known as Sabah). 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. Background Strategic situation and planning Codenamed Operation Oboe Six, the battle was part of the second phase of the Allied operations to capture the island of Borneo. North Borneo had been occupied by troops from the Imperial Japanese Army since early 1942 following the Japanese invasion of Borneo; prior to this the area had been a British territorial possession. Following its occupation, the area's oil resources had been exploited for the Japanese war effort. The island's population had also been subjected to harsh occupation policies. This had led to a revolt at Jesselton in late 1943, which was suppressed by the Japanese with heavy civilian casualties. The first stage of the Allied campaign in Borneo had begun in May 1945 when a brigade-sized force had been put ashore on Tarakan, on the north-eastern side of Borneo. The operation in North Borneo was planned by General Douglas MacArthur's South West Pacific Area command. Designed with three phases—preparatory bombardment, forced landings, and an advance—the objective of the Allied operation was to establish "an advanced fleet base" for the British Pacific Fleet in Brunei Bay, which offered the Allies a deep-water port, to enable subsequent naval operations. Further objectives included capturing the vast oil and rubber supplies available in the area and re-establishing British civil administration. It was also intended that