'Tradewind' was the US seizure of Morotai island at the northern end of the Halmahera islands group of the Molucca islands archipelago in the Japanese-occupied Netherlands East Indies by Major General John C. Persons’s 31^st Division of Major General Charles P. Hall’s XI Corps of Lieutenant General Walter C. Krueger’s 6^th Army, the main surface combat element of General Douglas MacArthur’s South-West Pacific Area (15 September/4 October 1944).

Located at about the mid-point between the Philippine islands group and the western end of New Guinea, the island of Morotai is part of the Halmahera islands of Maluku archipelago in the eastern part of what was then the Japanese-occupied Netherlands East Indies: the island is 48 miles (77.25 km) long with a maximum width of 28 miles (45 km), and has an area of some 690 sq miles (1785 km²). Most of the island’s interior, rising to a maximum height of 3,575 ft (1090 m), is rugged and covered in thick jungle, and the most extensive of the few lowland areas is the Doroeba plain in the island’s south-western corner. This included a protected anchorage with a good roadstead to the west of the Gila peninsula, but possessed almost no facilities in 1941. The beaches to the east of the Gila peninsula are free of reefs and suitable for landings, while the rest of the island is fringed with reefs, and much of the west coast is mangrove swamp. In 1941 there were no roads and only a few trails created by the local population, which numbered about 9,000 persons.

The Japanese took control of Morotai island early in 1942 during their campaign to take the Netherlands East Indies, but initially neither garrisoned nor developed it. The island first became important to the Japanese early in 1944 when they began to develop the neighbouring and somewhat larger island of Halmahera, to the south-west across the narrow Morotai Strait, as a focal point for the defence of the southern approaches to the Philippines islands group. Under the overall supervision of General Korechika Anami’s 2^nd Area Army, headquartered on Celebes island with responsibility for the defence of Halmahera, Batjan and Morotai islands as well as Celebes island, Lieutenant General Nobuo Ishii’s 32^nd Division arrived on Halmahera in May 1944 to defend the island and its nine airstrips, and two battalions of the division’s 211^th Regiment were deployed to Morotai, where work began on an airstrip on the Doroeba plain near the village of Pitoe. Work on the airstrip was abandoned as a result of drainage problems, however, and both battalions were withdrawn in July 1944 to reinforce the garrison of Halmahera island. The garrison left on Morotai island was no more than 500 men of the army’s 32^nd Division and Rear Admiral Ichihei Yokokawa’s naval 26^th Special Base Force.

General Douglas MacArthur, commanding the South West Pacific Area initially selected Halmahera island as the objective for his forces' next advance toward the Philippine islands group, but a shortage of amphibious warfare vessels, in combination with 'Ultra' decrypts showing that the Japanese were reinforcing Halmahera island, persuaded him in July 1944 to change the objective to Morotai island as the location for air bases and naval facilities which were needed to support the liberation of Mindanao island in the Philippine islands group, a task planned for 15 November within the 'Victor' campaign. While Morotai island was undeveloped, it was preferred to Halmahera island as it was believed that the larger and much better defended island would be very costly for the US forces to capture.

The capture of Morotai island was scheduled to begin with an amphibious assault by the 'Daredevil' Task Force on 15 September 1944, the same day as the 'Stalemate II' landing of Major General William H. Rupertus’s 1^st Marine Division on Peleliu island in the Palau islands group. This would allow elements of Admiral Chester W. Nimitz’s US Pacific Fleet to protect both operations from a Japanese counterattack.

In preparation for 'Tradewind' and 'Stalemate II', the US Navy decided to launch a major carrierborne air offensive into the area using Vice Admiral Marc A. Mitscher’s Task Force 38 in the period between 28 August and 24 September. TF38 sailed from from Eniwetok atoll on 28 August with four carrier task groups 1. On 31 August, 1 September and 2 September TG38.4 attacked Iwo Jima and Chichi Jima, and on 1/2 September the cruisers and destroyers shelled these islands. The Japanese landing ship T-105 was damaged at Chichi Jima, and warplanes from Enterprise severely damaged the fast landing ship T-4 on 1 and 2 September. On 3 September Rear Admiral Allen E. Smith’s TG12.5 (heavy cruisers Chester, Pensacola and Salt Lake City and destroyers Dunlap, Fanning and Reid) shelled Wake island with air escort provided by the carrier Monterey. On 6, 7 and 8 September all four task groups attacked Palau with 16 carriers. On 9 and 10 September TG38.1, TG38.2 and TG38.3 attacked airfields on Mindanao with 12 carriers, meeting very little resistance, and from 12 to 14 September the weight of the attacks was therefore moved to the area of the Visaya islands group in the central part of the Philippine islands group, sinking 21 Japanese vessels and damaging many more.

On this day the aeroplane of Ensign Tillar, one of Hornet's pilots, was shot down, Tillar being rescued by Filipinos and then taken off by a floatplane from the cruiser Wichita: Tillar was able to inform his superior officers that the Japanese force on Leyte was small, and because air reconnaissance showed few airfields there, Halsey therefore proposed that the planned landing on Yap island in the Palau islands group be called off and the 'King II' landing on Leyte brought forward by two months from 20 December to 20 October. This proposed was accepted at the 'Octagon' (2^nd Quebec) conference on 16 September.

The aircraft of TG38.1 attacked Mindanao again on 14 September, when the Japanese fast transport T-5 was sunk. In 2,400 sorties over these three days, US carrierborne aircraft destroyed more than 200 Japanese aircraft. Also on 14 September, the destroyers Farenholt, McCalla and Grayson shelled radar installations at the mouth of the Davao Gulf. After being replenished, the 12 carriers attacked airfields on Luzon on 21 and 22 September, particularly in the area of Manila, and then airfields in the Visaya islands group once again on 24 September. On 21 September carrierborne aircraft sank the destroyer Satsuki, corvette Kaibokan 5, five tankers and 16 freighters, and followed on on 24 September with the minelayer Yaeyama, torpedo boat Hayabusa, seaplane tender Akitsushima, submarine chaser Ch-32, two tankers and seven freighters.

These preliminary air attacks to suppress the Japanese air forces in the vicinity of Morotai island had been triggered by the fact that Allied intelligence at this time estimated the presence of 582 Japanese aircraft, of which 400 were in the objective area, within 400 miles (645 km) of Morotai island. The Allied air forces therefore flew heavy raids on airfields in the Halmahera, Celebes, Ceram, Ambon, Boeroe and other areas even as US Navy carrierborne aircraft attacked Japanese air units based at Mindanao and mounted further attacks on Halmahera and Celebes islands. By 14 September it was estimated that only 60 aircraft remained in the vicinity of Morotai island.

The carrierborne air campaign therefore destroyed more than 1,000 Japanese aircraft, and sank or otherwise rendered unserviceable 150 ships of all sizes. The only US losses were 54 aircraft in combat and 18 in accidents.

To preserve the vital element of surprise, the Allies did not bombard Morotai island before the landing, and undertook only a few photo-reconnaissance flights over the island. An Allied Intelligence Bureau patrol had been landed in the island in June, but the information it collected was not forwarded to Lieutenant General Walter C. Krueger’s US 6^th Army, which had overall responsibility for the US Army forces involved in 'Tradewind'. Although the 'Tradewind' Task Force possessed little information on the invasion beaches or Japanese positions, the 6^th Army did not land any of its own reconnaissance patrols on Morotai island as it was feared that their detection might warn the island’s defenders that an attack was imminent.

The 'Tradewind' Task Force embarked in the shipping of the invasion convoy at several bases in north-western New Guinea, and undertook landing rehearsals at Aitape and on Wakde island at a time early in September. The convoy gathered at Maffin Bay on 11 September, and departed for Morotai island on the following day. The convoy’s voyage was uneventful, and the convoy arrived off Morotai island during the morning of 15 September without having been detected by Japanese forces.

At the time of the 'Tradewind' landing, Morotai was defended by some 500 Japanese troops, of which the most capable were those of Major Takenobu Kawashima’s 2^nd Provisional Raiding Unit. This had reached Morotai in stages between 12 and 19 July 1944 to replace the two battalions of the 32^nd Division, and comprised four companies in which Japanese officers commanded conscripted Formosan soldiers. Small elements of several infantry, military police and support units (including elements of the 26^th Special Base Force) were also present on the island. Kawashima deployed the bulk of his combat force in the south-western sector of the island, while the remaining elements were deployed in look-out posts and detachments around Morotai’s coast. The largest of these outposts was at Cape Sopi, on the island’s north-eastern end, and consisted of about 100 men.

The Allied force to take Morotai outnumbered the Japanese by more than 100/1. The task force had been established on 20 August and numbered 40,105 soldiers and 16,915 men including elements of the USAAF and Royal Australian Air Force. The 'Tradewind' Task Force came under the immediate command of Krueger’s 6^th Army, and its main combat elements were the headquarters of Hall’s XI Corps, Persons’s 31^st Division (124^th, 155^th and 167^th Infantry) and the 126^th Regimental Combat Team of Major General William H. Gill’s 32^nd Division. These were supported by a large anti-aircraft group and several engineer units, and the task force also included large numbers of construction and other line of communications units whose role was the swift development of the island as a major base to support further operations.

Major General Edwin D. Patrick’s 6^th Division was designated as the force’s reserve, but remained on New Guinea.

MacArthur accompanied the 'Tradewind' Task Force on board the cruiser Nashville, but exercised no direct command role. The landing force was supported by powerful air and naval forces. Lieutenant General George C. Kenney’s US 5^th AAF was tasked with direct support of the operation from airfields at Biak, Noemfoor and Cape Sansapor, while Major General Nathan F. Twining’s US 13^th AAF and Air Commodore Arthur H. 'Harry' Cobby’s Australian 1^st Tactical Air Force conducted strategic missions in the Netherlands East Indies and the Philippine islands group.

The naval force which transported and supported the assault formations of the 7^th Amphibious Force was Rear Admiral Daniel E. Barbey’s Task Force 77 and organised into two attack groups, four reinforcement groups, a support group and an escort carrier group. Departing Aitape, Wakde and Hollandia on 10 September, the two attack groups were White Force with Barbey on board the headquarters ship Wasatch, and Red Force with Rear Admiral William M. Fechteler on board the destroyer Hughes. The landing fleet comprised two Australian attack transports, five US troop-carrying destroyer conversions, 45 tank landing ships, 24 infantry landing craft, 20 tank landing craft, and one dock landing ship. Support and escort were provided by 24 destroyers, four frigates, 11 rocket-armed tank landing craft, six patrol craft, two fleet tugs, and four yard minesweepers.

Naval cover for the operation and pre-landing bombardment was provided by Rear Admiral Russell S. Berkey’s TF75 comprising TG75.1 with the US light cruisers Phoenix, Boise and Nashville and US destroyers Hutchins, Beale, Bache, Daly, Abner Read and Bush, and Commodore J. A. Collins’s TG75.2 with the Australian heavy cruisers Australia and Shropshire, Australian destroyers Arunta and Warramunga, and US destroyers Mullany and Ammen.

Air support was provided by Rear Admiral Thomas L. Sprague’s TG77.1 with the escort carriers Sangamon, Suwanee, Chenango, Santee, Saginaw Bay and Petrof Bay, and eight destroyers.

Thus the attack and reinforcement groups responsible for transporting the assault force and subsequent support units comprised 24 destroyers, four frigates, two Australian infantry landing ships, five troop-carrying destroyer conversions, one dock landing ship, 24 infantry landing craft, 45 tank landing ships, 20 tank landing craft, and 11 rocket-armed infantry landing craft. As noted above, the support group comprised two Australian heavy cruisers, three US light cruisers, and eight US and two Australian destroyers. The escort carrier group comprised six escort carriers and 10 destroyer escorts and provided anti-submarine and combat air patrol. A fast carrier group with two fleet carriers, two light carriers and escorting ships was also available to support TF77 if needed.

As little in the way of opposition was expected, the landings on Morotai island were planned for the Gila peninsula, a location as close as possible to the selected airfield sites on the Doroeba plain. Two beaches on the south-western coast of the island were selected as suitable landing sites and designated as Red and White beaches.

The Allied plan called for all three regiments of the 31^st Division to be landed across the Red and White beaches on 15 September, and then to advance inland to secure the airfield sites as quickly as possible. As the island’s interior was of no military value, the Allies intended to advance no farther than the Doroeba plain, on which two airfields (one large and the other small) were then to be constructed.

The landings began at 06.30 on 15 September. Allied warships completed a two-hour bombardment of the landing area to suppress any Japanese forces there: this set some local villages on fire but caused few Japanese casualties as they had no significant units in the area. The first wave of US troops landed at 08.30 and met no opposition. The 155^th and 167^th Regimental Combat Teams landed on Red beach and the 124^th Regimental Combat Team on White beach. The assault troops then re-formed into their tactical units and advanced inland. By the end of the day the 31^st Division had secured all of its D-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 was unable to offer any resistance to the overwhelming Allied force but instead withdrew inland in good order. As a result of the unexpectedly bad beach conditions, the lack of resistance was fortunate for the US forces. While the limited pre-invasion intelligence had suggested that Red and White beaches were capable of supporting an amphibious landing, they were in fact highly unsuitable for this purpose. Both beaches were muddy and difficult for landing craft to approach as a result of rocky ridges and coral reefs. Men and equipment had therefore to be landed through deep surf, which slowed the operation and resulted in the loss of a significant quantity of equipment. Like many of his men, MacArthur had to wade through chest-high surf when he came ashore. On the morning of D-day a survey party determined that a beach on the peninsula’s south-east coast, in the angle of Pitoe Bay opposite White beach, was much better suited to the operation of tank landing ships, and this Blue beach then became the primary landing point from 16 September.

The 31^st Division continued its advance inland on 16 September, met little opposition and secured the planned perimeter round the airfield area during the afternoon of that day. After 16 September, combat operations on Morotai were limited to patrol actions which aimed to hunt down small Japanese parties, though the Japanese did mount an unsuccessful counterattack on 18 September.

The limited nature of the Japanese resistance meant that the US ground troops did not require the heavy air support which was available to them, and the fast carrier group was released for other duties on 17 September. The six escort carriers remained in support, however, but their aircraft saw little action, and four of them were released on 25 September and the last two on 4 October.

From 17 September the 126^th Infantry made a number of landings along Morotai’s coast and offshore islands to establish radar stations and observation posts. These landings were generally unopposed, though US patrols which were landed in the northern part of Morotai made numerous contacts with small Japanese parties.

On 20 September the 31^st Division advanced farther inland to secure an expanded perimeter. This expansion was necessary to accommodate bivouacs and supply installations after MacArthur’s headquarters had decided to expand airfield construction. 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 one company of the 126^th Infantry attacked a well-emplaced Japanese force near Wajaboeta on the island’s west coast and was repulsed. 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. The US casualties during the battle for Morotai totalled 30 dead, 85 wounded and one missing. The Japanese casualties were much higher, with more than 300 being killed and 13 captured.

According to Japanese histories, the Japanese military had quickly recognised the threat which would be posed to their forces in the Philippine islands group should the Allies develop airfields on Morotai island. In an attempt to disrupt the airfield construction programme, therefore, the Japanese commanders on Halmahera island despatched significant numbers of reinforcements across the Morotai Strait to Morotai island between a time late in September and November. These troops included the main body of the 211^th Regiment, the 3/210^th Regiment and three raiding detachments. Colonel Kisou Ouchi, commander of the 211^th Regiment, assumed command of the Japanese forces on Morotai island during 12 October.

Allied codebreakers were often able to warn the forces on Morotai island of Japanese attempts to run the blockade, and PT-boats were therefore able to destroy many of the barges used as troop transports, but were unable to put a complete end to the Japanese build-up. The Japanese counter-offensive on the island was not successful, however, largely as a result of troops' high rates of disease and the their lack of adequate food, ammunition and medical supplies, most of which fell victim to the Allied air and naval blockade.

As a result, while the 2^nd Provisional Raiding Unit attacked the US perimeter on several occasions, the reinforcements were unable to mount larger attacks and thus could not effect any major disruption of the Allies' airfield construction. The surviving Japanese then fell back into the centre of Morotai island, where many soldiers died from disease or starvation. The last Japanese supply barges from Halmahera island reached Morotai island on 12 May 1945.

Late in December 1944 the 136^th Infantry of Major General Percy W. Clarkson’s 33^rd Division was delivered to Morotai island from New Guinea to attack the 211^th Regiment in the west of the island. After landing on the west coast, the 136^th Infantry moved into Japanese-held territory on 26 December and closed on the Japanese position from the south-west and north. The 136^th Infantry was supported by a battalion of the 130^th Infantry advancing overland from the Doroeba plain, artillery on islands off the coast and 100 porters provided by the local population. The 3/167^th Infantry was also committed to the operation, making a notably difficult march from Morotai island’s south coast into the interior to prevent the Japanese from scattering into small groups in the island’s central mountains.

Early in January 1945 the US forces established the fact that two of the 211^th Regiment's battalions were on Hill 40, about 4 miles (6.5 km) to the north of the Allied perimeter. The resulting attack on this position began on 3 January, when the 1 and 2/136^th Infantry advanced from the south-west in the face of determined resistance. The two battalions expended considerable quantities 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 an artillery bombardment, and reached the main Japanese position in the afternoon. During this period the 3/136^th Infantry advanced on Hill 40 from the north, and destroyed the 3/211^th Regiment in a series of engagements. This Japanese battalion had been stationed on the coast to receive supplies from Halmahera island, and had mounted several unsuccessful attacks on the US battalion’s beach-head after it landed in December.

The 136^th Infantry completed its attack on Hill 40 on 5 January as its 1^st and 2^nd Battalions advanced from the west and south-west and the 3^rd Battalion from the north, meeting little resistance. The 1^st and 2^nd Battalions continued to the north in pursuit of Japanese remnants until 14 January 14, by which time the regiment claimed to have killed 870 soldiers and taken another 10 prisoner for the 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 three days earlier. In mid-January the 136^th Infantry was withdrawn to the Allied perimeter, and here rejoined the 33^rd Division, which was staging through Morotai island for the 'Mike I' landing on Luzon in the Philippines islands group.

Lieutenant General Einosuke Sudo’s (from 1 February Lieutenant General Shigeji Hakugin’s) 7^th Air Division continued to raid Morotai island for months after the Allied landing: the formation flew 82 raids (179 sorties) against Morotai island between 15 September 1944 and 1 February 1945. The aircraft used in these raids flew from Ceram and Celebes islands, and staged through airfields on Halmahera island. While 54 of the raids caused no damage, the others resulted in the destruction of 42 and damage to 33 Allied aircraft, and also killed 19 men and wounded 99 more. The most successful of these raids was that of the night of 22/23 November, which destroyed 15 and damaged eight Allied aircraft. Regular air raids ceased at the end of January 1945, though a final attack took place on 22 March.

The US night-fighters had only limited success as the raiders were normally detected only shortly before they entered the zones covered by the US anti-aircraft guns, which downed most of the 26 Japanese aircraft lost over Morotai island.

The initial four squadrons of PT-boats operating from Morotai island were reduced to a single squadron by February 1945, but the boats were active until the end of the war with patrols in the waters round Morotai island, and also with operations into the Japanese-occupied Netherlands East Indies for raids on Japanese positions and to support Australian and Dutch reconnaissance parties. By the end of the war the PT-boats had undertaken nearly 1,300 patrols and destroyed 50 barges and 150 small craft off Morotai and Halmahera islands.

The 31^st Division remained on Morotai island until 12 April 1945, when it departed for service in the 'Victor V' operations in the south-eastern part of Mindanao in the Philippine islands group, and was replaced by Major General Harry H. Johnson’s 93^rd Division, which was a segregated African-American formation used primarily for security and construction tasks. Once established on Morotai island, the division started a programme of intensive patrolling designed to destroy the remaining Japanese units on the island. At this time most of the Japanese were located along the island’s west coast, and generally remained close to the native gardens that were their primary source of food. The 93^rd Division landed patrols along Morotai island’s west and north coasts from April onward, and these were involved in large numbers of scattered skirmishes with small Japanese forces. One of the division’s main goals was the capture of Ouchi, who was taken by a patrol of the 25^th Infantry on 2 August as the highest-ranked Japanese officer to be captured before the end of the war.

The development of Morotai island into a military base began even before the island had been declared secure. Some 12,200 service troops had been landed in 73 tank landing ship loads and 19 Liberty ship loads by the end of September 1944, and work on the completion of the Japanese airstrip as a fighter base began on 16 September but was not completed until 29 September. Meanwhile, work had begun on a much larger bomber base on the south coast on 18 September, and this was completed on 5 October as Wama Drome. Morotai’s permanent fighter garrison arrived as soon as Wama Drome was open and assumed responsibility for the island’s air defence from TF77’s escort carrier group. Another, and even longer, airstrip was built to the north of Wama Drome between 23 September and 17 October as Pitoe Airfield. Although the air base construction required the destruction of villages, the US and Australian airfield engineers working on the airstrips were assisted from 1 October by about 350 local labourers who had been recruited through the Netherlands East Indies civil authorities.

As a result of a revision to Allied plans, Morotai island now played a much more significant role in the liberation of the Philippine islands group than had been originally intended. In September 1944 the planned invasion of Mindanao island in November was postponed in favour of a the 'King II' landing on Leyte island in the central part of the Philippine islands group during October. The air bases on Morotai island were the closest Allied air facilities to Leyte island, and fighters and bombers based on the island attacked targets in the southern part of the Philippine islands group and the Netherlands East Indies in support of the landing on Leyte island during 25 October.

After airfields had been completed on Leyte, Morotai island was also used as a staging base for land-based fighters and bombers flying to the Philippine islands group. Morotai island remained an important Allied base even after Leyte had been secured, however. Aircraft of the US 13^th AAF and Australian 1^st Tactical Air Force 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 Lieutenant General Sir Leslie Morshead’s Australian I Corps for the 'Oboe' operations against Japanese-occupied Borneo. On 9 September 1945 General Sir Thomas Blamey, commander-in-chief of the Australian Military Forces, accepted the surrender of Lieutenant General Fusataro Teshima’s 2^nd Army at a ceremony on Morotai island.