The 'Battle of Morotai' was a campaign fought largely between US and Australian forces against Japanese forces on Morotai, a small island just to the north of Halmahera in the Japanese-occupied Netherlands East Indies (15 September/4 October 1944).

However, although the campaign was officially deemed to have ended in October 1944, intermittent fighting continued on the island to the end of World War II in August 1945.

The battle began when US and Australian forces landed on the south-western corner of Morotai, which the Allies needed as a base to support their campaigns to liberate the Philippine islands group from October 1944. The landed forces greatly outnumbered the island’s Japanese defenders and secured their objectives in two weeks, but the Japanese landed reinforcements on the island between September and November, but lacked the supplies needed for any effective attack on the Allied defensive perimeter. Intermittent fighting continued until the end of the war, with the Japanese troops suffering heavy loss of life from disease and starvation.

Morotai is a rugged and densely forested island lying to the north of Halmahera. It has an area of some 902 sq miles (2337 km²), including the little Rao island that lies to the west of Morotai proper. The island stretches 50 miles (80 km) on its north-south axis and no more than 26 miles (42 km) on its east/west axis. The island’s largest town is Daruba, on the southern coast, and almost all of Morotai’s numerous villages are coastal settlements. Between Halmahera and the islets and reefs of the western coast of Morotai is the Morotai Strait, which is about 6.2 miles (10 km) wide. The Doroeba plain in Morotai’s south-western corner is the largest of the island’s few lowland areas. Before the outbreak of war, Morotai had a population of 9,000 and had not been commercially developed. It formed part of the Netherlands East Indies and was ruled by the Dutch through the Sultanate of Ternate. The Japanese occupied Morotai early in 1942 but did not garrison or develop it.

Morotai’s development into an Allied base began shortly after the landing, and two major airfields were ready for use in October. These and other base facilities played an important role in the liberation of the Philippine islands group during 1944 and 1945. PT-boats and aircraft based at Morotai also harassed Japanese positions in the occupied Netherlands East Indies. The island’s base facilities were further expanded in 1945 to support the Australian-led 'Oboe' campaigns on Borneo, and Morotai remained an important logistical hub and command centre until the Dutch re-established their colonial rule.

Early in 1944, Morotai became an area of importance to the Japanese military when it started developing the neighbouring and considerably larger Halmahera island as a focal point for the defence of the southern approaches to the Philippine islands group. In May 1944, the Imperial Japanese army’s 32^nd Division arrived on Halmahera to defend the island and its nine airstrips. The division had suffered heavy losses when the 'Take' convoy carrying it from China came under attack by US submarines. Two battalions of the 32^nd Division's 211^th Regiment were initially deployed to Morotai to develop an airstrip on the Doroeba plain, but were both withdrawn to Halmahera in the middle of July when the airstrip was abandoned as a result of drainage problems. Allied codebreakers detected the Japanese build-up on Halmahera and also Morotai’s weak defences, and passed this information to the relevant planning staff.

In July 1944, General Douglas MacArthur, commander of the South-West Pacific Area, selected Morotai as the location for air bases and naval facilities needed to support the liberation of Mindanao in the Philippine islands group, currently scheduled for 15 November. While Morotai was undeveloped, it was preferred over Halmahera as the larger and much better-defended island was judged too difficult to capture and secure. The occupation of Morotai was designated 'Tradewind' and the landing was scheduled to take place on 15 September 1944, the same day as the 1^st Marine Division landed on Peleliu, in the Palau islands group, in 'Stalemate II'. This schedule allowed the main body of Admiral Chester W. Nimitz’s US Pacific Fleet to undertake the simultaneou protection of both operations against potential Japanese counterattacks.

As little opposition was expected on Morotai, Allied planners decided to land the invasion force close to the intended airfield sites on the Doroeba plain. Two beaches on the south-western coast of the island were selected as suitable landing sites, and were designated Red Beach and White Beach. The Allied plan called for all three infantry regiments of Major General Clarence A. Martin’s 31^st Division to be landed across these beaches on 15 September to drive swiftly inland and secure the plain. As Morotai’s interior had no military value, the Allies did not intend to advance beyond a perimeter needed to defend the airfields. Planning for the construction of airfields and other base installations was also undertaken before the landing, and tentative locations for these facilities had been selected by 15 September.

At the time of the Allied landings, Morotai was defended by some 500 Japanese soldiers. The main unit was the 2^nd Provisional Raiding Unit, which had arrived on the island piecemeal between 12 and 19 July 1944 to replace the 32^nd Division's battalions when the latter were withdrawn. The 2^nd Provisional Raiding Unit comprised four companies of Japanese-officered Formosan soldiers. Small elements of several other infantry, military police and support units were also present on the island. The 2^nd Provisional Raiding Unit's commander, Major Takenobu Kawashima, deployed his unit in the south-western sector of the island and used the smaller units to establish look-out positions and detachments around Morotai’s coast. The largest of these outposts was on the island’s north-eastern end at Cape Sopi, which numbered about 100 men. The Japanese force was too small and widely dispersed to be able to mount an effective defence, so the 32^nd Division instructed it to build dummy camps and use other deceptions in an attempt to trick the Allies into thinking that Morotai was held in strength.

The Allied force assigned to Morotai outnumbered the island’s defenders by more than 100/1. The 'Tradewind' Task Force was created on 20 August under the command of Major General Charles P. Hall and numbered 40,105 US Army soldiers and 16,915 US Army Air Forces and Royal Australian Air Force personnel. The 'Tradewind' Task Force came under the overall command of Lieutenant General Walter C. Krueger’s US 6^th Army, and its main combat elements were the headquarters of Hall’s XI Corps, the 31^st Division and the 126^th Regimental Combat Team of the 32^nd Division. These units were supported by engineers and a large anti-aircraft group. The 'Tradewind' Task Force also included large numbers of construction and other line of communications units, whose task it was to complete the swift development of the island into a major base. The 6^th Division was designated the force reserve but remained on the mainland of New Guinea. MacArthur accompanied the force on board the large light cruiser Nashville, but was not in direct command.

The landing force was supported by powerful air and naval forces. Lieutenant General George C. Kenney’s US 5^th Army Air Force provided direct support while Major General Paul B. Wurtsmith’s US 13^th Air Force and the RAAF’s No. 10 Operational Group undertook strategic missions in the Netherlands East Indies and the Philippine islands group. The naval force was designated Task Force 77 and was organised into two attack groups, four reinforcement groups, one support group and one escort carrier group. The attack and reinforcement groups were responsible for transporting the assault force and subsequent support units, and comprised 24 destroyers, four frigates, two Australian LSIs, five APDs, one LSD, 24 LCIs, 45 LSTs, 20 LCTs and 11 rocket-armed LCIs. The support group was made up of two Australian heavy cruisers, three US light cruisers, eight US destroyers and two Australian destroyers. The escort carrier group comprised six escort carriers and 10 destroyer escorts, and provided anti-submarine and combat air patrol capabilities. TF38.4 with two fleet carriers, two light carriers, one heavy cruiser, one light cruiser and 13 destroyers was also available to support TF77 if required.

Preliminary air attacks to suppress the Japanese air forces in the Morotai region began in August 1944. At this time, the Allied intelligence services estimated that there were 582 Japanese aircraft within 400 miles (640 km) of Morotai, of which there were 400 in the objective area. The Allied air forces conducted heavy raids on airfields in the Halmahera, Celebes, Ceram, Ambon, Boeroe and other areas. US Navy carrierborne aircraft also attacked Japanese air units based on Mindanao in the Philippine islands group and mounted further attacks on Halmahera and Celebes. These attacks were successful, and by 14 September it was estimated that only 60 aircraft remained in the Morotai region.

To preserve surprise, the Allies undertook no pre-landing bombardment of Morotai and conducted only a few photographic reconnaissance flights over the island. An Allied Intelligence Bureau patrol had been landed on the island in June but the information it collected was not passed on to the 6^th Army. Although the 'Tradewind' Task Force had little information on the invasion beaches or Japanese positions, the 6^th Army did not land any of its own reconnaissance patrols on Morotai for feat that this could warn the island’s defenders that an attack was imminent.

The 'Tradewind' Task Force embarked in the ships of the invasion convoy at several bases in north-western New Guinea, and made landing rehearsals at Aitape and Wakde island early in September. The convoy gathered in Maffin Bay on 11 September and departed for Morotai on the following day. The passage was without undue incident, and the convoy arrived off Morotai on the morning of 15 September without having been detected by the Japanese.

The 'Battle of Morotai' began at 06.30 on 15 September. Allied warships conducted a two-hour bombardment of the landing area to suppress any Japanese forces there. The bombardment set several villages on fire, but caused few Japanese casualties as they did had few troops in the area.

The first wave of US troops landed at 08.30 and did met no opposition. The 155^th and 167^th Regimental Combat Teams landed on Beach Red on the left flank and the 124^th Regimental Combat Team on Beach White on the right. Once ashore, the assault troops assembled into their tactical units and rapidly advanced inland. By the end of the day the 31^st Division had secured all its first-day objectives and held a perimeter 2,000 yards (1830 m) inland. There was little fighting and casualties were very low on each side. The 2^nd Provisional Raiding Unit could offer no resistance to the overwhelming Allied force, and withdrew inland in good order. Aircraft of Lieutenant General Einosuke Sudo’s 7^th Air Division, based on Ceram and Celebes, began a series of nightly air raids against Morotai on 15 September, but these had little effect.

The lack of resistance was fortunate for the Allies as a result of the unexpectedly poor beach conditions. While the limited pre-invasion intelligence suggested that Beaches Red and White were capable of supporting an amphibious landing, they were in fact highly unsuitable. Both beaches were muddy and difficult for landing craft to approach because of the presence of rocky ridges and coral reefs. As a result, soldiers and equipment had to be landed through deep surf. This delayed the operation and caused a large quantity of equipment to be damaged. On the morning of 15 September, a survey party determined that a beach on Morotai’s southern south was altogether better suited to LST operations and, designated Beach Blue, this became the primary Allied landing point from 16 September.

The 31^st Division continued its advance inland on 16 September, still meeting little opposition, and secured the planned perimeter line around the airfield area that afternoon. From 17 September, the 126^th Infantry landed at several points on Morotai’s coast and offshore islands to establish radar stations and observation posts. These operations were generally unopposed, although patrols landed in northern Morotai made numerous contacts with small Japanese groups. The 2^nd Provisional Raiding Unit attempted but failed to infiltrate into the Allied perimeter on the night of 18 September.

A detachment of the Netherlands Indies Civil Administration was responsible for civil affairs on Morotai. This detachment landed on 15 September, and re-established Dutch sovereignty over Morotai’s civilian population. Many local civilians subsequently provided the team with intelligence on Japanese dispositions on Morotai and Halmahera and others acted as guides for US patrols.

On 20 September, the 31^st Division advanced farther inland to secure an expanded perimeter. This was necessary to provide room for additional bivouac areas and supply installations after MacArthur’s headquarters had decided to expand airfield construction on the island. The advance met little resistance and was completed in one day. On 22 September, a Japanese force attacked the headquarters of the 1/167^th Infantry but was easily repulsed. On the following day, a company of the 126^th Infantry unsuccessfully attacked a fortified Japanese unit near Wajaboeta on the island’s western coast. The 126^th Infantry resumed its attack on 24 September and secured the position. US forces continued intensive patrolling until 4 October when the island was declared secure. US casualties during the initial occupation of Morotai island totalled 30 men killed, 85 wounded, and one missing. Japanese casualties were much higher, numbering more than 300 men killed and 13 taken prisoner.

The US ground force did not require the heavy air support available to it, and the fast carrier group was released for other duties on 17 September. The six escort carriers remained in support, but their aircraft saw little action. Four of the escort carriers were released on 25 September, and the remaining two departed on 4 October. The destroyer escort Shelton was sunk by the Japanese submarine Ro-41 on 3 October while escorting the escort carrier group. Several hours later, a Grumman TBF Avenger single-engined bomber from the escort carrier Midway attacked Seawolf 20 miles (32 km) to the north of the point at which Shelton had been torpedoed in the mistaken belief that this was the submarine responsible. After dropping two bombs, the TBF guided Richard M. Rowell to the area and the destroyer escort sank Seawolf after five attempts, killing all the submarine’s crew. It was later determined that while Seawolf was in a designated 'submarine safety lane', the escort carrier pilots had not been properly briefed on the lane’s existence and location, and that the submarine’s position had not been provided to Richard M. Rowell.

The US Navy established a PT-boat base at Morotai on 16 September when the tenders Mobjack and Oyster Bay arrived with the 41 boats of PT-boat squadrons 9, 10, 18 and 33. The PT-boats' primary mission was to prevent the Japanese from moving troops from Halmahera to Morotai, and established a blockade of the strait between the two islands.

Elements of the 31^st Division embarked from Morotai in November to capture several islands off New Guinea from which Japanese outposts could observe Allied movements. On 15 November 1,200 men of the 2/167^th Infantry and attached units were landed at Pegun island in the Mapia islands group; on the next day, Bras island was attacked. The Mapia islands group was declared secure on 18 November after resistance from 172 Japanese of the 36^th Division had been overcome. On 19 November, a force of 400 US troops built around Company F, 124^th Infantry, occupied the Asia islands group without meeting any opposition. These were the first offensive operations overseen by Lieutenant General Robert L. Eichelberger’s US 8^th Army, and the naval commander for both operations was Captain Lord Ashbourne of the Royal Navy on board the British minelayer Ariadne. Radar and LORAN navigation stations were later established on the islands.

The rapid development of Morotai into a major military base, designated as Naval Base Morotai, was a key goal of the operation. Pre-invasion plans called for the completion of three large airstrips within 45 days of 15 September, with the first to be operational immediately after the landing. The plans also included accommodation and supply facilities for 60,000 air force and army personnel, a 1,900-bed hospital, bulk fuel storage and handling installations and ship docking facilities. To construct these facilities, the 'Tradewind' Task Force included 7,000 engineer service troops, of whom 84% were American and 16% Australian.

Work began on base facilities even before Morotai had been declared secure. Survey parties began transit surveys of the airfield sites on 16 September, and determined that their planned alignment was unworkable. Plans to complete the Japanese airfield were also abandoned, as it would have interfered with larger airfields to be built to the east. It was instead cleared and used as an emergency strip. Work on the first new airstrip, called Wama Drome, began on 23 September after the site had been cleared. By 4 October Wama Drome’s runway was operable for 5,000 ft (1525 m) and was supporting heavy bomber raids on Balikpapan in Borneo. Construction of the even larger Pitu Drome, which was to have two runways parallel to Wama Drome, began late in September, and by 17 October the new airfield had a usable 7,000-ft (2135-m) runway. Construction work was accelerated from 18 October after Admiral Raymond A. Sprance’s US 3^rd Fleet was withdrawn from the provision of direct support for the 'King II' landing in Leyte island in the Philippine islands group. When the two airstrips were completed in November they possessed three large runways and hardstandings for 253 aircraft, including 174 heavy bombers. Although the air base construction required the destruction of villages, the US and Australian engineers were aided from 1 October by about 350 labourers locally recruited by the Dutch civil affairs detachment.

Other base facilities were erected in parallel with the construction of the airstrips. Work on fuel storage facilities began shortly after the landing, and the first of these was ready on 20 September. A jetty for oil tankers and a larger tank farm were completed early in October, and the enlargement of storage facilities continued until November, when capacity for 129,000 barrels (20500 m³) of fuel was available. Several docks capable of accommodating Liberty ships were constructed on Morotai’s western coast, the first of them being completed on 8 October. In addition, 20 LST landings were constructed on Beach Blue to facilitate the loading and unloading of these ships. Other major construction projects included an extensive road network, a naval installation, 28,000 sq ft (2600 m²) of warehousing, and clearing land for supply dumps and bivouacs. A 1,000-bed hospital was also built after the original plans for a 1,900-bed facility had been revised. The main difficulties encountered in this entire process were those associated with overcoming the mud resulting from unusually heavy rains and finding sufficient fresh water supplies.

A revision to Allied plans meant that Morotai played a much greater role in the liberation of the Philippine islands group than had been originally envisaged. The invasion of Mindanao was postponed in September 1944 in favour of a landing on Leyte in the central part of the island group on 25 October. The air bases at Morotai were the closest Allied airstrips to Leyte, and fighters and bombers based on the island attacked targets in the southern Philippines and Netherlands East Indies in support of the Leyte landing. After airfields had been completed on Leyte, Morotai was also used as a staging point for fighters and bombers on their way to the Philippine islands group.

The Japanese military had for some time recognised that its forces in the Philippine islands group would be threatened if the Allies developed airfields on Morotai. In an attempt to disrupt the airfield construction programme, therefore, the Japanese army commanders on Halmahera sent large numbers of reinforcements to Morotai in the period between late September and November. These troops included the main body of the 211^th Regiment, the 3/210^th Regiment and three raiding detachments. The commander of the 211^th Regiment, Colonel Kisou Ouchi, assumed command of the Japanese forces on Morotai on 12 October. Allied codebreakers were often able to warn the forces on Morotai of attempts to run the blockade, and PT-boats destroyed a large number of the barges the Japanese used to transport troops from Halmahera. The Allies were, however, unable to being the Japanese build-up to a complete halt.

The Japanese counter-offensive on Morotai was not successful. The troops brought to the island suffered from high rates of disease and it proved impossible to bring sufficient supplies through the Allied air and naval blockade. As a result, while the 2^nd Provisional Raiding Unit raided the US perimeter on several occasions, the reinforcements were unable to mount larger attacks and did not impede Allied airfield construction activities. The Japanese force subsequently withdrew into the mountain area of central Morotai where many soldiers died of disease or starvation. The last Japanese supply barges from Halmahera reached Morotai on 12 May 1945.

Later in December 1944, the US 33^rd Division’s 136^th Infantry was shipped to Morotai from New Guinea to destroy the 211^th Regiment in the west of the island. After landing on the island’s western coast, the US regiment moved into Japanese-held territory on 26 December and advanced on the Japanese position from the south-west and north. The 136^th Infantry was supported by one battalion of the 130^th Infantry advancing overland from the Doroeba plain, artillery units stationed on islands off Morotai’s coast and 100 civilian porters. The 3/167^th Infantry also participated in this operation and made a difficult march from Morotai’s southern coast into the interior to prevent the Japanese from scattering into small groups in the island’s mountains.

Early in January 1945, the US force determined that two battalions of the 211^th Regiment were at Hill 40, about 4 miles (6.4 km) to the north of the Allied perimeter. The attack on this position began on 3 January when the 1 and 2/136^th Infantry advanced from the south-west and encountered strong resistance. The regiment used a large quantity of ammunition in this attack, and aerial resupply was needed to replenish its supplies. Both US battalions resumed their attack on the following day with the support of a highly effective artillery bombardment, and reached the main Japanese position in the afternoon. During this period. the 3/136^th Regiment advanced on Hill 40 from the north, and destroyed the 3/211^th Regiment in a series of actions. This Japanese battalion had been stationed on the coast to receive supplies from Halmahera and mounted several unsuccessful attacks on the US battalion’s beach-head after it had landed in December.

The 136^th Infantry completed its attack on Hill 40 during 5 January. The 1 and 2/136^th Infantry advanced from the west and south-west and the 3/136^th Infantry from the north, meeting little resistance. The 1 and 2/136^th Infantry continued to the north in pursuit of Japanese remnants until 14 January, by which time the regiment claimed to have killed 870 Japanese soldiers and captured 10 for a loss of 46 killed and 127 wounded and injured. The 3/167^th Infantry linked with the 136^th Infantry on 7 January after overrunning the main Japanese radio station on the island on 4 January. In the middle of January, the 136^th Infantry was withdrawn to the Allied perimeter, where it rejoined the 33^rd Division, which was staging through Morotai en route for the Allied 'Mike I' landing on Luzon island.

The 7^th Air Division continued to raid Morotai for months after the Allied landing, this campaign involving 179 sorties between 15 September 1944 and 1 February 1945. The aircraft used in these raids flew from Ceram and the Celebes and landed at airfields on Halmahera before proceeding to their targets. While 54 of the raids caused no damage, the others resulted in the destruction of 42 Allied aircraft and damage to another 33. Allied casualties from air attack were 19 men killed and 99 wounded. The most successful of these raids was that of the night of 22 November, when 15 Allied aircraft were destroyed and eight damaged. The regular Japanese air raids ceased at the end of January 1945, though a final attack took place on 22 March. USAAF night-fighters had only limited success as the raiders were usually detected only shortly before they entered anti-aircraft gun defended zones: these guns shot down most of the 26 Japanese aircraft lost over Morotai. The official history of the USAAF’s night-fighter force states that Morotai 'was probably the most difficult task undertaken by American night fighters during World War II' as a result of the difficulty of detecting incoming raiders.

The PT-boat force at Morotai had been reduced to a single squadron by February 1945, but remained active until the end of the war. As well as patrolling around Morotai, the boats operated in the eastern part of the Netherlands East Indies to raid Japanese positions and support Australian and Dutch scouting parties. In May 1945 PT-boats and the Australian 'Z' Special Unit rescued the Sultan of Ternate along with his court and harem during an operation codenamed 'Project Opossum' after he had been mistreated by the Japanese. By the end of the war the PT-boats had conducted nearly 1,300 patrols and destroyed 50 barges and 150 small craft off Morotai and Halmahera.

The 31^st Division remained on Morotai until 12 April 1945, when it departed for commitment in the 'Victor IV' and 'Victor V' elements of the liberation of Mindanao, and was replaced by Major General Harry H. Johnson’s 93^rd Division, which was a segregated African American formation, and was used mainly for security and labour tasks during the war. Once established on Morotai, the division undertook intensive patrols with the aim of destroying the Japanese force remaining on the island. At this time most of the Japanese on Morotai were located along the island’s western coast, and generally stayed close to civilian gardens. The 93^rd Division landed patrols along Morotai’s western and northern coasts from April onward, and fought scattered skirmishes with small Japanese forces. One of the division’s main goals was to capture Ouchi, and this was achieved by a patrol of the 25^th Infantry on 2 August. The US force also used propaganda broadcasts and leaflets, with some success, to encourage Japanese soldiers on Morotai to surrender.

Morotai remained an important Allied base after Leyte had been captured. Aircraft of the 13^th AAF and Australian 1^st Tactical Air Force (formerly No. 10 Operational Group) were based at Morotai and attacked targets in the Netherlands East Indies and southern part of the Philippine islands group until the end of the war. From April 1945, the island was also used by the Australian I Corps to mount the 'Oboe' landings of the Borneo campaign. Australian army engineers expanded the base facilities on Morotai to support these. As a result of overcrowding, some Australian camp sites were located outside the US perimeter.

Morotai was the scene of a number of surrenders following the surrender of Japan. About 660 Japanese on Morotai capitulated to the Allied forces after 15 August. The 93^rd Division also accepted the surrender of the 40,000 Japanese troops on Halmahera on 26 August after the Japanese commander had been brought to Morotai on a PT-boat. On 9 September, the Australian army’s commander, General Sir Thomas Blamey, accepted the surrender of the Japanese 2^nd Army on the Australian I Corps' sports ground at Morotai. Private Teruo Nakamura, the last confirmed Japanese hold-out on Morotai or elsewhere, was captured by Indonesian air force personnel on 18 December 1974.

The facilities on Morotai continued to be used extensively by the Allies in the months after the war. The Australian force responsible for the occupation and military administration of the eastern part of the Netherlands East Indies was headquartered on Morotai until April 1946, when the Dutch colonial government was re-established.