9th Division 727th Amphibian Tractor Battalion Thirty-Seventh Army The Battle of North Borneo took place during the Second World War between Allied and Japanese forces.

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.

Meanwhile, minesweepers began to clear sea lines of communication for the large Allied naval task force that was assigned to support the operation.

[7] Part of the all-volunteer Second Australian Imperial Force, the 9th Division was a veteran formation, having previously served in North Africa, the Middle East and New Guinea.

[14] The division had experienced a high turn over in personnel following its service in the Huon Peninsula campaign as soldiers were medically discharged or transferred to other units.

[23] It had been raised in Japan during the second half of 1944 and arrived in Borneo late that year as the area's garrison troops were reorganised for defence against future Allied landings.

[24] By mid-1945, the brigade had been heavily depleted by its overland movement from the north-eastern part of Borneo prior to the Allied landings and was at around half strength; its troops were largely inexperienced, lightly equipped and were suffering from poor morale.

After concentrating at Morotai Island in May, where complex landing rehearsals were undertaken,[13] the assault force, consisting of 85 ships—mainly from the US Navy—departed in early June, preceded by minesweepers and survey vessels, as well as the naval attack group.

[29] With this support, the main Allied landings were largely unopposed as the Japanese defenders had withdrawn from the beaches on the peninsula and Muara Island had been abandoned completely.

Light opposition was overcome and the town and airfield were secured late on the first day, after minor clashes with Japanese outposts and troops fighting amongst the aircraft dispersal bays.

[30] Despite the initial progress the fighting on Labuan intensified during this time as the Japanese defenders retreated inland to a heavily fortified position known as "the Pocket" and attempted to hold the Australians along the dense jungle ridges and thick swamps.

[32] Despite considerable artillery and armoured support, a company-level attack by the 2/28th Battalion was turned back on 14 June, and as a result further preparatory fires were called upon to soften up the Japanese defences.

[31] At this stage of the war, Australian commanders were under strict orders to limit their casualties, and "avoid unnecessary risks", utilising fire support where possible to reduce Japanese defences prior to attacking.

[34][35] The second Allied landing that took place on 10 June, consisted of two battalions of Brigadier Victor Windeyer's 20th Brigade—2/15th and 2/17th Battalions—landing at Muara Island and on the mainland peninsula north of Brooketon, supported by a second squadron of Matildas from the 2/9th Armoured Regiment.

[36] The troops that had landed near Brooketon on the mainland advanced on Brunei, which was captured on 13 June by the 2/17th Battalion after several minor section and platoon level actions over several days.

[39] At Seria the Australians found the 37 oil wells ablaze, having been deliberately lit by the Japanese defenders as they withdrew, and engineers from the 2/3rd Field Company were called up to put out the fires, a task which took over three months to complete.

[32] Having secured its objectives, the 20th Brigade then began patrolling operations, using landing craft to move quickly along the various rivers and streams that punctuated the coastline.

During July, guerrillas assigned to Operation Semut captured Marudi, on the Barem River, as part of efforts to disrupt the Japanese withdrawal from Miri.

A strong Japanese counter-attack retook the village from the lightly armed Semut operatives, after which the guerrillas linked up with conventional Australian infantry from the 2/17th Battalion to capture it once again on 15 July.

[47] Following this, reinforcements in the form of two companies from the 2/28th Battalion were transferred from Labuan to take over rear area security while plans were made for the main attack on Beaufort.

[52] Elsewhere, on 1 July, the Australian 7th Division carried out the final stage of the Allied operation to secure Borneo, landing at Balikpapan, on the south-east coast.

[52] Following the capture of Papar, the Australians ceased offensive actions on Borneo and the situation remained largely static until a ceasefire came into effect in mid-August.

[56] As a result of the ceasefire, the planned Allied invasion of Japan was no longer required and the strategic gains provided by the capture of North Borneo were arguably negated; this included development of Brunei Bay into a naval base, which ultimately never occurred.

[66] They were also tasked with liberating the Allied civilian internees and prisoners of war that were being held at Batu Lintang camp in Kuching, Sarawak,[67] and with disarming the guerrillas that had been assigned to Operations Agas and Semut.

[69] Initially this process was slow as there were few troops able to relieve the Australian forces in Borneo and as such only long service personnel were released for return to Australia.