Late in March 1945, planning elements of the 9th Australian Division, commanded by Major-General G F Wootten left the Atherton Tableland in advance of the rest of the division, and emplaned for Morotai. They were followed by 26th Brigade Group, which moved from Australia prepared for an immediate operation-the capture of Tarakan, a small island off the east coast of Borneo. The principal object was to capture the airfield for development and use in future operations on the mainland.

Tarakan Island is situated off the delta of Sesa River in north-eastern Borneo. Before the war its oil fields produced yearly 6,000,000 barrels of what was reputed to be the world's purest oil. Fringed with mangrove swamps and a few sandy beaches, it has an interior of rolling wooded hills. The town of Tarakan has for its port Lingkas, on the south-west coast, with docking facilities and a safe harbour. Japanese strength at Tarakan was estimated at between 1500 and 4000 troops including l000 naval personnel. Subsequent to the landing it was considered that the Japanese force on Tarakan consisted of 1750 combat troops plus 350 Japanese civilians who were impressed for military duty at the time of the landing. The plan envisaged a landing on Tarakan Island by 26th Brigade Group, commanded by Brigadier D A Whitehead. Included under his command were two RAAF Airfield Construction Squadrons, one boat company of US 593 Engineer Boat and Shore Regiment, and one company of US 727 Amphibian Tractor Battalion and one company of a Netherlands East Indies infantry Battalion. Transport was supplied by ships of Amphibious Group Six and support by units of Task Group 781 and RAAF Command, with 13th US Army Air Force in support.

It was decided to make the landing at Lingkas beach. This would enable heavy mechanical equipment to be hurried up to the airfield along an existing surfaced road linking the port and field. There were several difficulties to be overcome. In addition to offshore obstacles, the gentle slope of the beach and the depth of mud would not permit the landing of heavy vehicles and guns until pontoon causeways had been placed and extensive beach exits constructed. In order to provide artillery support for the actual landing, the brigade commander decided to land one field battery at Sadau Island the day before the main landing, with a protective force made up of 2/4th Commando Squadron. Sadau Island lies some 6000 yards to the north-west of Lingkas beach. As the island had a good landing beach, no known obstacles and was believed to be very lightly held, little difficulty was expected in landing the battery. In fact, the island was found to be bare of Japanese troops.

In outline the brigade commander's plan was as follows: On P-day minus one day, the landing of the field battery on Sadau Island and the breaching of the beach obstacles by the engineers; on P-day, the name given to the day of the landing) an assault landing by two Battalions,2/23rd and 2/48th); 2/24th Battalion and the remainder of the force to be on call. Mine sweeping was to be undertaken during the four days before the operation. It was anticipated that the Japanese would endeavour to use burning oil in his defence of the beaches, but systematic bombing destroyed or breached every oil tank on the island.

P-day was originally fixed for 2g-April but was postponed to the1 May because of more favourable tides. Rehearsals for the operation were held at Morotai and on Kokoja Island off the coast. On 26-April the force allotted for the Sadau Island landing and the breaching of the obstacles sailed from Morotai followed the next day by the main assault convoy. It was not troubled by Japanese aircraft, and the only attempted naval interference was one submarine, which was believed to have been sunk on the night before the main landing) and shore-based torpedoes fired into the transport area early on P-day. One of these torpedoes grazed a ship but did not explode.

The landing at Sadau Island went according to plan, and in three hours the guns of a battery of 2/7th Field Regiment were firing in support of the engineers at Lingkas.

The breaching of the obstacles at Lingkas was a triumph for the sappers. Demolition parties drawn from 2/l3th Field Company were given the task of making eight 30-foot gaps in four rows of underwater obstacles on Red and Green beaches, to let the assault troops through; and four 60-foot gaps on Yellow Beach for the passage of LSTs. Two breaching operations were made on the morning and afternoon of the day before the landings. The sappers moved to the beaches in L.C.V.Ps and LVTs and struggled waist-deep through mud to place their charges. Detachments from 2/3rd Pioneer Battalion acted as gun crews on the LVTs, and covering fire was also given by 25 pounders from Sadau Island and warships Smoke-laying aircraft were also used. Despite the heavy mud and sporadic sniping and mortar fire from the shore, the task was successfully carried out and the thoroughly exhausted sappers were evacuated without casualty. This achievement was one of the most vital contributing factors to the success of the whole operation.

On P-day, for an hour and a half, from first light, cruisers and destroyers poured shells into the beach area. From the land came flashes as rocket-firing gunboats ran close inshore to cover the assault craft, while four flights of heavy bombers dropped their bombs along the foreshore. On both beaches the leading waves of the assault Battalions moved through the gaps in the obstacles to land practically dry-shod. There was no opposition from the beach itself or within the limits of the first objective. It was apparent that the Japanese had withdrawn inland, although he could obviously have put up a very effective resistance to the landing on the beach itself from strongly built concrete pillboxes dug into the embankment.

Within an hour of landing 2/48th Battalion struck some slight opposition on the feature immediately north-east of Lingkas tank farm, but continued to advance and secured its portion of the covering position later in the day. Stiff resistance held up 2/23rd Battalion on a ridge north-west of Milko, which was captured the next day. This enabled the Battalion to advance northward and eastward, one company overcoming Japanese resistance in the King's Goss area. By nightfall on the second day, apart from isolated pockets, the only part of the covering position not held was Hospital Ridge, where the Japanese were strongly entrenched in bunkers and tunnels. This hold-up seriously affected the development of the beach maintenance area, as the road to the north of the contested feature was needed to complete a traffic circuit. The same day 2/48th Battalion occupied Lyons. Against some opposition 2/24th Battalion advanced rapidly through Sturt, Wills, Frank and Essex, making successful use of tanks and flame-throwers. Many mines and booby-traps were encountered-on a far greater scale than previously encountered by Australian troops in the Pacific theatre-and in addition to a bomb-disposal platoon, sappers and RAAF engineers were kept busy clearing mined areas.

In the airfield area the going was hard owing to the terrain, stiff resistance, and the great number of mines and booby traps. One company overcame these difficulties and occupied Airstrip Ridge. Another company cleared Anzac Highway, where the Japanese ineffectively fired oil in a ditch as a defensive measure. In the Peningki-Baroe area two tanks silenced a troublesome nest of heavy and light machine guns which had menaced vehicles moving along a section of Anzac Highway. The Japanese fought desperately and the position was not finally cleared out until the next day. The 2/48th Battalion had patrols advancing on Peter, Sykes and Butch. It was at Sykes that the Japanese made one of his strongest counterattacks, but C Company held the ridge. The main feature in the centre of Tarakan township was strongly attacked by 2/4th Commando Squadron and occupied after two days' heavy fighting. Hospital Ridge was finally cleared on the third day, tanks assisting the infantry. This completed the occupation of the covering position, and opened up Collins Highway as a traffic circuit. On the same day, Brigadier Whitehead obtained approval to withdraw 2/3rd Pioneer Battalion from 2nd Beach Group to relieve 2/23rd Battalion, which then moved to the airfield area and came in contact with the Japanese to the east and north-east.

In the afternoon a patrol of 2/24th Battalion worked round to the west of Rippon, the dominating feature north of the airfield, and reported that the Japanese had apparently abandoned it after two days of heavy artillery fire, giving the Australian control of the airfield. Work began immediately to clear the field of bombs and mines in preparation for the use of mechanical equipment. This ended the first phase of the operation, after four days of hard fighting. The next phase began with 2/4th Commando Squadron and 2/48th Battalion advancing in conjunction to clear the features Jones, Peter and Otway, and the low ground between Otway and the Tarakan feature. A simultaneous attack was then made on the high ground, the commandos moving along Snags Track to reach the objective without opposition; but 2/48th's northward thrust was stopped at a difficult point along the ridge leading to the objective. After patrolling the area for some days, the Battalion outflanked the Japanese positions and in the subsequent attack occupied the ridge.

At the same time 2/3rd Pioneer Battalion advanced with two companies eastward along John's Track and found Japanese positions in depth on each side. Persistent attacks by the pioneers, supported by heavy artillery and naval concentrations and Napalm bomb air strikes, had their reward on 14-May when the features Helen and Sadie were occupied. At the same time elements of the pioneers reached the coast and seized the Japanese defences. In the fight for the Helen feature the Victoria Cross was posthumously won by Corporal John Bernard Mackey. The citation for his award states that:

Corporal Mackey was in charge of a section of the 2/3rd Australian Pioneer Battalion in the attack on the feature known as Helen, East of Tarakan town. Led by Corporal Mackey the section moved along a narrow spur with scarcely width for more than one man when it came under fire from three well-sited positions near the top of a very steep, razor-backed ridge. The ground fell away almost sheer on each side of the track making it almost impossible to move to a flank so Corporal Mackey led his men forward. He charged the first Light machine-gun position but slipped and after wrestling with one enemy, bayoneted him, and charged straight on to the Heavy Machine-Gun which was firing from a bunker position six yards to his right. He rushed this post and killed the crew with grenades.

He then jumped back and changing his rifle for a sub-machine-gun he attacked further up the steep slope another Light Machine-Gun position which was firing on his platoon. Whilst charging, he fired his gun and reached within a few feet of the enemy position when he was killed by Light Machine-Gun fire but not before he had killed two more enemy. By his exceptional bravery and complete disregard for his own life, Corporal Mackey was largely responsible for the killing of seven Japanese and the elimination of two machine-gun posts, which enabled his platoon to gain its objective, from which the Company continued to engage the enemy. His fearless action and outstanding courage were an inspiration to the whole battalion. (London Gazette: 8 November 1945.)

Patrols of 2/24th Battalion fanned out over a wide area to the west, north and east. Within four days one platoon had penetrated along the Anzac Highway as far as Djoeata, where they encountered Japanese troops but cleared the village without much trouble. The Netherlands infantry company had advanced southward along the road from Peningki area to Karoengan and by 10 May had reached the sawmills at Karoengan without seeing the Japanese. This meant that the right flank was clear from District IV to Karoengan. On 13-May the company landed at Cape Pasir jetty without opposition and cleared the features Spike, Spear and Peach. Sixteen days after the landing the Australian forces had cut through to the east coast, the Netherlands East Indies troops occupied the southern peninsula, and two-thirds of the island, including the Pamoesian and Djoeata oil fields, was in Australian hands.

At this stage a policy of extensive patrolling and ambushes coupled with harassing fire had the effect of confining Japanese activities to very definite and limited areas, and threatening his freedom of movement above ground. A feature of the attacks on Japanese strongholds was the co-operation and accuracy of supporting aircraft and artillery, and naval bombardment. In particular the dropping of inflammable belly tanks on Japanese positions proved very effective as large burnt-out patches in vacated areas testified. At night the Japanese employed infiltration attacks extensively. Small parties, usually armed with explosives, endeavoured to pierce Australian lines with the intention of damaging installations, but they had very little success. Japanese positions were steadily and progressively overcome, and by the end of May the Japanese had been beaten back to the Fukukaku positions. On 30-May the brigade came under direct command of First Corps, as the 9th Division was about to undertake the invasion of the Brunei Bay area on the north-west coast.

After a period of softening up a general advance began in all sectors on 14-June. The main drive from the south-west by 2/23rd Battalion penetrated the area, while co-ordinated attacks from the north-west by 2/24th Battalion and from the south-east by 2/48th Battalion cleaned out remaining Japanese positions. By the evening of the Is-June the Fukukaku area was completely over-run and mopping up was almost complete. Organised resistance by the Japanese as a force was ended and survivors retreated in independent groups to the north and the north-east. The remaining Japanese were hunted by patrols, and many were captured attempting to leave by improvised rafts.

On the morning of 27-June a colourful religious ceremony was held in the Pamoesian oil fields at the first pump to be restored. In accordance with the native practice a cow was slaughtered and its head buried near the pump house, the object of this being to bury all the evil spirits and ensure that no bad accidents occurred in the field. Shortly after 10 am on 29-June, the first plane-excluding the tiny Auster reconnaissance aircraft-landed on the Croydon strip, to be followed during the day by twenty Kittyhawks. Next day twelve Spitfires arrived, while two Lightnings, which had been providing air cover for the great 7th Division convoy en route to Balikpapan came in to refuel. In two months of unrelenting fighting 26th Brigade had achieved its main objects, and by 31 July, 1499 Japanese dead had been counted, with an estimated additional dead of 235. Guerrilla forces dispatched thirty-nine and 314 had been taken prisoner, a total of 2087.

The cost to Australian forces, however, had been considerable. The killed, (including Lt T C Derrick, VC, DCM of 2/48th Battalion) totalled 233, wounded 644, while 1434 had been evacuated through sickness.