This was the US seizure of the Admiralty islands group in the Bismarck archipelago some 200 miles (320 km) to the north of New Guinea and to the west of New Ireland (29 February/18 May 1944).
In July 1942 the US Joint Chiefs-of-Staff had authorised a series of operations against the Japanese bastion at Rabaul, which flanked and thereby effectively blocked any Allied advance to the north-west along the north coast of New Guinea island toward the Philippine islands group or to the north in the direction of the main Japanese naval base at Truk in the Caroline islands group. In keeping with the Allied 'Germany first' overall grand strategy, the immediate aim of these operations was not the defeat of Japan but merely the reduction of the threat posed by Japanese aircraft and warships based at Rabaul to air and sea communications between the west coast of the USA and Australia.
An inter-Allied agreement of March 1942 had divided the Pacific theatre into two main elements, the South-West Pacific Area under General Douglas MacArthur, and the Pacific Ocean Areas (North Pacific Area, Central Pacific Area and South Pacific Area) under the overall command of Admiral Chester W. Nimitz. Rabaul fell within MacArthur’s area of responsibility, but the initial US offensive operations in the south-eastern part of the Solomon islands group came under Nimitz, one of whose sub-areas was the South Pacific Area commanded first by Vice Admiral Robert L. Ghormley, then from 18 October 1942 by Admiral William F. Halsey.
The Japanese reaction to the US 'Watchtower' offensive on Guadalcanal was more violent than had anticipated, and it was February 1943 before the Guadalcanal campaign was brought to a successful conclusion.
Meanwhile MacArthur’s land forces, most of them Australian, fought off a series of Japanese offensives in Papua in the Kokoda Track campaign, Battle of Milne Bay, Battle of Buna and Gona, and Battle of Wau.
At a conference of March 1943 to fix the plans for forthcoming operations in the Pacific theatre, the US Joint Chiefs-of-Staff approved 'Elkton III', the latest iteration of MacArthur’s 'Elkton' basic plan for an advance on Rabaul, and decided, as a result of the limited resources available to the South-West Pacific Area, especially heavy bombers, to postpone the final stage of the plan, namely the capture of Rabaul, into 1944. By July 1943, the Joint Chiefs-of-Staff had revised their strategic thinking to consider not the capture of Rabaul but rather the bypassing of this Japanese base area, although the US Navy would still require a forward fleet base in the region. The Admiralty islands group, which was already part of the 'Elkton' plan, could serve this purpose, as the islands included substantial areas of flat land suitable for the construction of airstrips and the location of other military installations, as well as Seeadler Harbour, which was an anchorage large enough to accommodate a naval task force. On 6 August 1943, therefore, the Joint Chiefs-of-Staff formally adopted a plan based on the neutralisation rather than capture of Rabaul, and scheduled the invasion of the Admiralty islands group for 1 June 1944.
Throughout January 1944, aircraft of the US Air, Solomons (AirSols) command based in the Solomon islands group to the south-east of New Britain, together with aircraft of the Royal Australian Air Force based on Kiriwina island in the Trobriand islands group to the south of New Britain, maintained a steady air offensive against Rabaul. Under this pressure, Vice Admiral Jinichi Kusaka’s 11th Air Fleet and Lieutenant General Kumaichi Teramoto’s 4th Air Army began to weaken, allowing the 'Squarepeg' landing to be made on 15 February on the Green islands group, which lies little more than 100 miles (160 km) from Rabaul. On 16/17 February, the US Pacific Fleet’s Task Force 58, under the command of Vice Admiral Marc A. Mitscher, attacked the main Japanese base at Truk in 'Hailstone'. Most Japanese aircraft were recalled to defend Truk, and 19 February saw the last significant interception of Allied aircraft over Rabaul.
Meanwhile, on 13 February, MacArthur had issued orders for the 'Brewer' assault against the Admiralty islands group on 1 April under the control of Lieutenant General Walter C. Krueger’s 6th Army, which was to use Major General Innis P. Swift’s 1st Cavalry Division (13,600 men), the 592nd Engineer Boat and Shore Regiment, and the 1st Marine Amphibian Tractor Battalion, totalling 25,974 men. Air support was to be provided by the RAAF’s No. 73 Wing (2,488 men), and 9,545 navy construction troops and and 7,103 army service troops were then to build the base. The 1st Cavalry Division had no previous combat experience, but was nonetheless seen as an elite formation, with a large number of regular officers and men.
Constituting the final target of the 'Elkton III' plan of March 1943, the Admiralty islands group of about 20 volcanic islands lies 200 miles (320 km) to the north of the mainland of North-East New Guinea and 360 miles (580 km) to the west of Rabaul on New Britain island, and is just to the south of the equator. The climate is therefore tropical, with temperatures and humidity which are always high, and an annual rainfall of 154 in (3.91 m). Tropical thunderstorms are common, and the period between December and May is that of the north-west monsoon, with the prevailing winds from that direction.
The islands of the Admiralty group have a total land area of about 800 sq miles (2020 km²), and are rugged and covered with jungle. Most of the coasts are fringed with coral reefs, leaving only a few small beaches suitable for landing operations. The largest of the islands is Manus, which is 49 miles (79 km) long on its east/west axis and 16 miles (26 km) wide on its north/south axis, with a central mountain range reaching 2,356 ft (718 m) and covered with tropical rain forest. The coast, which was at the time largely uncharted, has numerous reefs, and the shore comprises mangrove swamp for the most part. Separated from Manus by the narrow Loniu Passage, Los Negros island is almost contiguous with Manus island and contains two important harbours in the form of Papitai on its west coast, which connects with Seeadler Harbour, and Hyane on its east coast. The two are separated by a sandy spit a mere 50 yards (46 m) wide. Los Negros is curved like an eccentric horseshoe on its side with the open end facing to the west, and constitutes a natural breakwater for Seeadler Harbour, the large bay which is otherwise enclosed by Manus to the south and a string of smaller islands (including Ndrilo, Hauwei and Pityilu) to the north. The main entrance was through a passage, 1.5 miles (2.4 km) wide, between Hauwei and Ndrilo islands. A superb natural anchorage, Seeadler Harbour is about 20 miles (32 km) across from east to west, and 6 miles (9.7 km) wide from north to south, with a maximum depth of 120 ft (37 m), and was of great strategic value in the South-West Pacific campaign.
The main settlement was Lorengau to the south of Seeadler Harbour.
The group had been a German possession before World War I, but was taken by Australian forces early in that conflict and then mandated to Australia in 1920 by the League of Nations. In 1939 there were only 44 Westerners, mostly plantation managers, on the islands, which had an indigenous Melanesian population of about 13,000. The islands produced small quantities of copra, turtle shells and pearls, the latter heavily exploited before the war by Japanese divers from the Caroline islands group to the north. The islands were also completely undeveloped, with no roads outside the immediate vicinity of Lorengau. A native trail ran along the north coast of Manus, and three trails crossed the interior mountains to the south coast.
In 1942 the Japanese had bombed Lorengau on 21 January, occupied Manus on 8 April with Colonel Yoshio Ezaki’s 51st Transport Regiment of Lieutenant General Hidemitsu Nakano’s 51st Division detached from Lieutenant General Takashi Sakai’s 23rd Army in China, and completed a 4,000-ft (1220-m) airstrip at Momote on Los Negros to the east of Seeadler Harbour. In 1943 the Japanese built a 3,300-ft 1005-m) airstrip to the north-west of Lorengau.
The Japanese defence of the Admiralty islands group was a responsibility of General Hitoshi Imamura’s 8th Area Army, which had its headquarters at Rabaul. During September 1943, as a result of its forces' failure to halt the Allied advances in New Guinea and the Solomon islands group, the Imperial General Headquarters had decided to withdraw Japan’s defensive perimeter in the south and central Pacific to a new line extending anti-clockwise from the Banda Sea to the Caroline islands group. Within this new scheme Imamura was to hold his portion of the new line, which included the Admiralty islands group, for as long a time as was possible in order to buy the time needed for the Japanese navy and army time to prepare 'decisive' counter-offensives against the Allied forces. Holding the Admiralty islands group was vital to the Japanese defensive plan as Allied possession of these islands would put the key Japanese stronghold at Truk within heavy bomber range. It seems that Imperial General Headquarters did not expect the Allies to move on the Admiralty islands group as quickly as they did, however, for Imamura was given until the middle of 1944 to complete the defensive preparations for his command.
Imamura looked for ways to reinforce the Admiralty islands group at a time between late 1943 and early 1944. In October 1943 he requested an infantry division for the islands, but no such formation was available. A subsequent proposal to transfer the 66th Regiment from the Palau islands group, where it was being rebuilt after suffering heavy losses, was also rejected as Imperial General Headquarters believed that Lieutenant General Hatazo Adachi’s 18th Army on New Guinea had greater need for this unit. The Japanese navy also rejected Imamura’s suggestion that a special naval landing force unit be dispatched to the islands. Imperial General Headquarters had a change of heart in January 1944, after the navy had decided that Seeadler Harbour would be an ideal forward base, and agreed to deploy the 66th Regiment to the Admiralty islands group following the Allied 'Director' landing at Arawe on 15 December 1943 and 'Dexterity' landing at Saidor on 2 January 1944, but the regiment’s deployment was cancelled after a ship carrying reinforcements for the regiment was sunk by the US submarine Whale with heavy loss of life on 16 January. Following this disaster Imamura directed Lieutenant General Sadaaki Kagesa to despatch one battalion of his 38th Division from New Guinea to the islands, and 750 men of the 2/1st Independent Mixed Regiment arrived there on the night of 24/25 January. A subsequent attempt to ship single infantry and artillery battalions to the islands was frustrated by Allied air and submarine attacks, but 530 soldiers of the 38th Division's 1/229th Regiment arrived on the night of 2 February, thereby increasing Ezaki’s strength to about 4,600 men. Most of these troop movements were detected by Allied intelligence.
As indicated above, during July 1943, after the decision had been taken not to assault and capture Rabaul, MacArthur was encouraged by the Joint Chiefs-of-Staff, who had discussed the strategy at the 'Quadrant' conference at Quebec in May 1943, to seize the Admiralty islands group. This was strategically located, had a magnificent anchorage at Seeadler Harbour, and possessed ample flat ground for the construction of airfields on Los Negros, to the east of the harbour. Moreover, the seizure of the Admiralty islands group would make its possible for MacArthur’s South-West Pacific Area command to avoid the planned 'Anchorage' by bypassing the major Japanese base area at Hansa Bay on New Guinea’s coast.
A target date of 1 January 1944 was initially set, but this was pushed back to 1 April by the 'Backhander' seizure of the Cape Gloucester at the western tip of New Britain, and by a dispute over the appropriate command arrangements as Halsey’s South Pacific Area command controlled the 'Seabee' construction units needed to build the naval base. The decision to make Halsey responsible for developing the base was not made until 28 February.
Aircraft of the US 5th AAF, which was commanded by Lieutenant General George C. Kenney, also heading the Allied Air Forces in the South-West Pacific Area, undertook a bombing campaign in January and early in February against both the Admiralty islands group any nearby airfields that might provide air support for the Japanese on the islands, in the process destroying an estimated 80 Japanese aircraft on the ground in the Admiralty islands during a single attack early in February.
On 22 February three North American B-25 Mitchell medium bombers of Kenney’s 5th AAF flew at low altitude over Los Negros, and the crews later reported that they had seen no signs of Japanese activity and believed that the islands had been evacuated as the airstrip was overgrown and there were no signs of men or vehicles. Kenney went to MacArthur and proposed that the apparently unoccupied islands be quickly taken by a small force. MacArthur chose to disregard intelligence, derived from radio intercepts, that there were between 4,000 and 5,000 Japanese still on the island. MacArthur therefore authorised a reconnaissance in force which could be developed into a full-scale assault if resistance proved light. Orders were therefore issued at 15.00 on 24 February for a reinforced squadron of the 1st Cavalry Division to carry out a reconnaissance in force in just five days time and, if this discovered that the Admiralty islands had indeed been evacuated, the islands would be occupied and a base developed. If the Japanese were still there in strength, the force could be withdrawn. MacArthur and Vice Admiral Thomas C. Kinkaid, commanding the Allied Naval Forces, South-West Pacific Area, would be present to make this decision, but otherwise delegated command to Rear Admiral William M. Fechteler, the commander of Amphibious Group 8 of Rear Admiral Daniel E. Barbey’s 7th Amphibious Force.
The target date was set for 29 February despite the fact that MacArthur’s forces could now expect to receive no aircraft carrier support from the Pacific Ocean Areas of Nimitz, who was not expecting the assault on the Admiralty islands group for another month.
Krueger and Swift had serious doubts about the assault, the latter believing that an initial force of at least 2,200 men was required. Krueger accordingly increased the initial landing force from MacArthur’s recommended 800 men to more than 1,000 men, the most that could be landed in a single lift with the shipping which was currently available. Krueger also ensured that there would be shipping available for a large follow-up force, which was the key to the operation if the reconnaissance in force became a serious invasion attempt. Rear Admiral Daniel E. Barbey’s VII Amphibious Force assembled a force of destroyers and destroyer transports for the reconnaissance force, assigning the slower tank landing ships and infantry landing craft for the delivery of the follow-up force.
Brigadier General Charles A. Willoughby’s South-West Pacific Area intelligence section did not agree with the airmen’s assessment that the islands were unoccupied and, drawing on 'Ultra' and Allied Intelligence Bureau reports from interrogations of local civilians, reported on 15 February that there were 3,000 Japanese troops in the Admiralty islands group, and on 24 February revised the estimate to 4,000. The intelligence staff attributed the lack of anti-aircraft fire to the Japanese logistical situation, believing it was a measure to conserve ammunition.
Krueger also believed that the islands had not been evacuated. In the original plan a team of 'Alamo' Scouts was to have undertaken a thoroughly reconnaissance of Los Negros island before the landing was committed, and Krueger now had a six-man party of 'Alamo' Scouts delivered to the south coast of Los Negros island by a Consolidated PBY Catalina flying boat under cover of a bombing raid on 27 February. After paddling ashore on a rubber raft, the the 'Alamo' Scouts reported at 06.45 that the south coast was 'lousy with Japs'. The reconnaissance patrol was extracted on the following day. Kenney doubted the reconnaissance patrol’s report, however, and MacArthur felt it was now too late to cancel the operation.
Fechteler’s Task Force 76 had set out on 27 February with Captain Jesse H. Carter’s Task Group 76.3, comprising the destroyers Drayton, Reid, Flusser, Mahan, Smith, Bush, Welles, Stevenson and Stockton each carrying some 57 troops, escorting TG76.2, comprising the troop-carrying destroyer conversions Humphreys, Brooks and Sands each carrying 170 troops. Fire support was provided by Berkey’s TG74.2, comprising the light cruisers Phoenix (with MacArthur and Kinkaid on board) and Nashville, and destroyers Daly, Hutchins, Bache and Beale.
The high-speed transport conversions of old destroyers were required in order to achieve surprise by reaching the Admiralty islands group in just five days, tank landing ships and infantry landing craft being too slow to cover the required distance in the time available.
This initial reconnaissance force was led by Brigadier General William C. Chase, commander of the 1st Cavalry Division’s 1st Cavalry Brigade, and included the three infantry troops and the heavy weapons troop of the 2nd Squadron, 5th Cavalry; one platoon of Battery B, 99th Field Artillery Battalion with two 75-mm (2.95-in) pack howitzers; the 673rd Anti-Aircraft Machine Gun Battery (Airborne); and 29 Australians of the Australian New Guinea Administrative Unit (ANGAU), who were to assist in gathering intelligence and dealing with the islanders.
If and when the decision to remain had been made, a follow-up force with the rest of the 5th Cavalry, 99th Field Artillery Battalion, 211th Anti-Aircraft Artillery Battalion and the 428-man 40th Naval Construction Battalion, and 2,500 tons of stores would depart Finschhafen under Swift’s command in six tank landing ships each towing one medium landing craft of Company E, 592nd Engineer Boat and Shore Regiment. These would be escorted by the destroyers Mullany, Ammen and Australian Warramunga, destroyer minesweepers Hamilton and Long, six tank landing ships and six mechanised landing craft. A third lift would see the reuse of these naval assets to deliver Brigadier General Verne D. Mudge’s 2nd Cavalry Brigade and the 7th Cavalry as and when required.
At the time of the US landing, the Japanese army forces in the Admiralty islands group comprised the 51st Transport Regiment, 2/1st Independent Mixed Regiment, 1/229th Regiment, and naval elements in the form of the 14th Base Force . Allied intelligence had identified the presence of all these units, although the designation of some of the units was not known. While the 1/229th Regiment was a veteran unit, it was short of equipment and lacked its battalion artillery. The 2/1st Independent Mixed Regiment was led by reserve officers who had seen service in the Chinese theatre, and most of its men were also reservists recalled to service but had seen no combat.
As noted above, the 51st Transport Regiment had built an airstrip near Lorengau on the north-eastern end of Manus island and had begun work on another on the Momote Plantation on Los Negros island. Lorengau was used as a staging point for aircraft moving between Rabaul and the several airstrips in North-East New Guinea. The importance of the Admiralty islands group to the Japanese increased as the result of Allied advances in New Guinea and New Britain, which closed other air routes. By February, both airstrips in the Admiralty islands group were unserviceable, however, and the anti-aircraft guns remained unused in an effort to conserve ammunition and conceal their positions. Ezaki had ordered his men not to move or fire in daylight.
The location selected for the landing on Los Negros island was a small beach on the south shore of Hyane Harbour near the Momote airstrip. The airstrip could be seized quickly, but the surrounding area was mangrove swamp, and the harbour entrance was only about 750 yards (700 m) wide. This made the undertaking somewhat problematical, but the US gamble was successful. The Japanese had not expected a landing in this location, and had concentrated their main strength for the defence of the beaches of Seeadler Harbour on the other side of the island.
The weather on 29 February was overcast with a low cloud ceiling that prevented most of the sorties which had been planned to provide air support, and in fact only three Consolidated B-24 Liberator heavy bombers and nine B-25 Mitchell medium bombers found the target. To compensate for the weakening of the air effort, the naval bombardment was extended for 15 minutes more than the planned duration. After arriving off the assault area, each destroyer transport lowered four Landing Craft, Personnel, Ramped (LCPRs), each of which carried its maximum load of 37 men who boarded by climbing over the parent vessel’s side and scrambling down cargo nets. The unarmoured LCPRs were still used because the destroyer transports' davits had not been strengthened to carry the armoured and therefore heavier Landing Craft, Vehicle, Personnel (LCVP).
The first wave landed without loss at 08.17, but once the naval bombardment lifted the Japanese emerged from their dug-outs and opened fire with machine guns and artillery. On returning with the men of the second wave, the landing craft came under a cross-fire from machine guns on each side of the harbour, and this fire became so heavy that the second wave was forced to turn back until the Japanese fire had been suppressed by the fire of the 5-in (127-mm) guns of destroyers. The third and fourth waves also came under fire.
Four of the 12 LCPRs had been damaged. Three were soon repaired, but could not be risked further, as the reconnaissance force could not be evacuated without them: an emergency plan provided for an APD to enter the harbour and lift the troops off from a jetty, but clearly this would be a measure of extreme desperation. Over the next four hours, the boats made trips to the beach, but only when it was believed destroyers had suppressed the Japanese fire, and heavy rain made the task less risky by reducing visibility. The last destroyer was unloaded at 12.50, and by this time the US Navy had lost two men dead and three wounded.
For the moment it was safer ashore, where the cavalrymen overran Momote airstrip. Sporadic opposition was not sufficient to prevent them from establishing their anti-aircraft machine guns on the beach, unload supplies, and send patrols inland. Two soldiers were killed and three wounded. At 16.00 MacArthur and Kinkaid came ashore, and after inspecting the position MacArthur decided that the assault would continue. After ordering Chase to hold his position until the follow-up force arrived, MacArthur returned to Phoenix. Fechteler’s ships departed at 17.29, the transports having unloaded and most of the bombardment force having exhausted its ammunition. Bush and Stockton remained to provide naval fire support as required.
At this time Chase concentrated his men into a tight perimeter. There was no barbed wire for the creation of passive defences, so the whole area had to be covered with fire for active defence. The ground was hard coral, which was good for runway construction but made the digging of foxholes difficult. The cavalrymen’s 12 0.5-in (12.7-mm) heavy machine guns were positioned in the front line. Fighting continued through the night as small groups of Japanese attempted to infiltrate the US position, and the expenditure of ammunition was so great that an ammunition airdrop was requested, and a break in the weather allowed three B-25 aircraft of Lieutenant Colonel Lawrence Tanberg’s 38th Bombardment Group to make a supply drop at 08.30. Four Boeing B-17 Flying Fortress aircraft of Colonel Joel G. Pitts’s 375th Troop Carrier Group each dropped three tons of supplies, including blood plasma, ammunition, hand grenades and barbed wire. Part of the ammunition drop fell outside the US perimeter, but for some reason the men who moved out to retrieve did not come under fire.
The Japanese were not expected to make another effort until night had fallen, but at about 16.00 it was discovered that a Japanese patrol had managed to infiltrate the perimeter in broad daylight and reach a point only 35 yards (32 m) of Chase’s command post. After a Japanese sniper had fired on the command post, Major Julio Chiaramonte, the task force’s intelligence officer, led four other men out to silence the sniper. As his party closed in, there was a series of explosions: three Japanese had committed suicide with hand grenades, while another had killed himself with his sword. The US cavalrymen counted 15 dead officers and sergeants, the former including Captain Baba, commander of the Japanese battalion which made the attack the preceding night. The Japanese launched another attack on the perimeter at 17.00, but could make little progress in the face of the now reinforced US firepower.
The following morning saw the arrival of the second echelon of some 1,500 cavalrymen and 428 naval construction personnel in six tank landing craft each towing one medium landing craft, escorted by Captain Emile Dechaineux’s three destroyers and two destroyer minesweepers. Supported by the fire of the destroyers Bush, Stockton and Welles, the landing ships and craft entered Hyane Harbour and beached, coming under mortar fire as they did so. LST-202, manned by a US Coast Guard crew, replied with 3-in (76.2-mm) and 40-mm Bofors guns. The LSTs were unloaded over the next seven hours. As ammunition, construction equipment and stores began to accumulate on the beach it became difficult to accommodate and make the correct dispersal of all these stores, and Chase ordered an attack to expand the perimeter.
Air support was requested. The B-25 bombers of Colonel Clinton U. Clue’s 345th Bombardment Group were intercepted by an estimated 15 Japanese fighters, but these were driven off by eight escorting Republic P-47 Thunderbolt fighters, whose pilots claimed eight Japanese aircraft shot down. Two B-17 bombers of the 69th Troop Carrier Squadron on a supply dropping run were also attacked, and the crews claimed to have shot down one of their attackers. Two of the four B-25 squadrons dropped their bombs in areas occupied by US troops, of whom two were killed and four wounded before the 12th Air Liaison Party could correct the error.
Both squadrons of the 5th Cavalry attacked at 15.00, taking all their objectives, and this allowed a larger defensive perimeter to be established. The 40th Naval Construction Battalion had landed expecting to work on Momote airstrip, but instead was ordered to use its equipment to clear fields of fire and construct fortifications; the battalion was also given a section of the perimeter to defend.A bulldozer dug out six trenches, and 10 men were allocated to each of these. The 'Seabee' ditch digger scooped out a 300-yard (270-m) trench as a second line of defence, and the airstrip’s revetments were transformed into heavy machine gun posts.
It was intended that the two destroyer minesweepers should sweep the entrance to Seeadler Harbour between Hauwei and Ndrilo islands, but fire from at least one Japanese 4-in (101.6-mm) gun on Hauwei island prevented the ships from entering the harbour. As commander of the destroyers supporting the forces ashore, Dechaineux then brought Ammen, Bush, Mullany and Warramunga around and bombarded the island. The Japanese guns ceased fire, but came back into action when another attempt was made to sweep the channel. Dechaineux then called off the effort, ordering the destroyer minesweepers join him. The destroyers bombarded the Japanese guns covering the entrance to Hyane Harbour to allow the tank landing ships to leave unmolested, though one of these ships left with between 20 and 30 truckloads of stores still aboard in the haste of a departure reflecting as desire not to remain after dark as a Japanese attack was expected. Dechaineux escorted the landing ships part of the way until ordered by Barbey to leave Ammen, Mullany, Warramunga and Welles off Los Negros. Ammen and Mullany shelled Hauwei island again in the morning, setting off a couple of ammunition dumps, but still came under accurate fire from four or five guns, and Dechaineux was forced to inform Barbey that he was unable to overcome the island’s guns.
On 5 March the third echelon of 1,410 troops arrived with TG76.1, comprising the destroyers Flusser, Drayton, Smith, Wilkes, Swanson, Nicholson, Stevenson, Thorn and Australian Arunta, and troop-carrying destroyer conversions Humphreys, Brooks and Sands. On 6 March Nicholson was damaged by the still unsilenced batteries at the entrance of Seeadler Bay, and TF74’s ships again shelled the islands on 7 March, raining a total of 64 8-in (203-mm), 4-in (102-mm) shells onto the Japanese positions.
By this time Krueger had become highly worried about the situation on Los Negros. In response to urgent request from Chase, Krueger arranged with Barbey for the movement of the rest of the 1st Cavalry Division to be accelerated as rapidly as possible. At Krueger’s request, the 2nd Squadron, 7th Cavalry would travel in the three destroyer transports, and other elements of the division were now scheduled to arrive on 6 and 9 March instead of 9 and 16 March. Krueger realised that Hyane Harbour was too small to allow the support of the whole of the 1st Cavalry Division, but there were good beaches around the Salami Plantation on Los Negros’s west coast, but before these beaches could be used, and a shore-to-shore operation against Manus from Los Negros also become possible, Seeadler Harbour had to be opened.
From the Japanese point of view, the battle was not going well. The Japanese had expected a landing inside Seeadler Harbour as this was the logical US objective, and had therefore concentrated their main strength around Lorengau airfield. The defence of the Momote airstrip and Hyane Harbour was the responsibility of 'Baba' Force, built around Baba’s 1/229th Regiment, and Ezaki ordered Baba to attack the beach-head. However, Ezaki feared that the Hyane Harbour landing was merely a diversion and, in combination with false reports of US activity at Salami, this persuaded him to retain the 2/1st Independent Regiment there instead of sending it to assist the 'Baba' Force. By 2 March, Ezaki had resolved to attack the Hyane Harbour beach-head with his whole force, but terrain difficulties and disruption by US artillery and Allied naval gunfire forced a postponement of the attack to the night of 3 March.
At 21.00, a single Japanese warplane dropped eight bombs, cutting telephone wires. Once the aeroplane had departed, yellow flares signalled the start of the Japanese assault in which the infantry was supported by mortar fire. Offshore, Dechaineux’s destroyers came under attack from four Mitsubishi G4M 'Betty' bombers.
The 1st Squadron, 5th Cavalry, was attacked by about two reinforced platoons, which were met by heavy automatic weapons and mortar fire. The thick jungle in this sector permitted a measure of Japanese infiltration, but the Japanese lacked the strength to overrun the position. The main Japanese attack was delivered by the 2/1st Independent Mixed Regiment from the direction of the canoe and boat skidway which the local population had earlier built to connect Hyane Harbour with Seeadler Harbour, together with detachments from the Porlaka area, and fell on the 2nd Squadron, 5th Cavalry. At this point the cavalrymen noticed a change in the Japanese tactics: instead of infiltrating silently as they had done before, they now advanced across the open, talking and in some cases singing. Their advance took them straight into anti-personnel mines and booby traps, which duly exploded, and then into the fields of fire of the US automatic weapons, including several 0.3-in (7.62-mm) Browning water-cooled machine guns, but nonetheless continued to advance. The guns of the 211th Coast Artillery (Anti-Aircraft) Battalion and 99th Field Artillery Battalion fired through the night, attempting to break up the Japanese attack from Porlaka.
Shortly after 24.00 Japanese barges attempted to cross Hyane Harbour, but these were engaged by anti-aircraft guns and did not reach the US positions. A 40-mm Bofors gun position was captured by the Japanese, but these were then driven off by the 'Seabee' personnel. The 5th Cavalry’s machine gunners killed so many Japanese that the 0.3-in (7.62-mm) machine guns had to be moved to get clear fields of fire.
By dawn, the Japanese attack had ended, and the Americans counted more than 750 Japanese dead in and around their positions; no prisoners had been taken. The US losses were 61 dead and 244 wounded, these figures including 'Seabee' losses of nine dead and 38 wounded. The night battle had resulted in the expenditure of very large quantities of ammunition, and Chase requested an airdrop. He also asked for Warramunga to fire on the skidway.
In the morning of 4 March there arrived the 2nd Squadron, 7th Cavalry, to relieve the 2nd Squadron, 5th Cavalry. On 5 March the divisional commander, Swift, arrived on board Bush and assumed command. He ordered the 2nd Squadron, 7th Cavalry, to attack across the skidway, and this meant that the 2nd Squadron, 5th Cavalry, had to be sent back into the line to relieve them. While the relief was taking place, however, the Japanese launched a daylight attack. This was repulsed by the cavalrymen, with the help of artillery and mortar fire, but the US attack had to be delayed until a time late in the afternoon. The attack ran into a Japanese minefield and was so slowed that by dawn the advance had managed top penetrate only as far as the skidway.
On 5 March a third wave arrived with TG76.1, comprising the destroyers Flusser, Drayton, Smith, Wilkes, Swanson, Nicholson, Stevenson, Thorn and Australian Arunta, and troop-carrying destroyer conversions Humphreys, Brooks and Sands, and during the morning of 6 March five tank landing ships, each of them again towing one medium landing craft, delivered into Hyane Harbour these 1,410 men of the the 12th Cavalry, other units and equipment including five tracked landing vehicles of the 592nd Engineer Boat and Shore Regiment, three M3 light tanks of the 603rd Tank Company, and 12 105-mm (4.13-in) howitzers of the 271st Field Artillery Battalion.
The 12th Cavalry was ordered to follow the 2nd Squadron, 7th Cavalry, in its advance to the north, and to capture Salami Plantation. The road to Salami Plantation was little more than a muddy track in which vehicles soon became bogged, however, and the Japanese also obstructed the route with ditches, felled trees and booby traps, all covered by snipers. But Warrant Officer 2nd Class R. J. Booker of the ANGAU used his local knowledge to guide the 12th Cavalry and the three tanks to Salami, where the Japanese put up a determined resistance which lasted for more than one hour. The tanks fired canister rounds into buildings and high explosive shells into the slits of Japanese bunkers.
The inhabitants of the area informed the ANGAU detachment that the Japanese had retreated across Seeadler Harbour to Papitalai Mission, which thus became the US force’s next objective: the 5th Cavalry was to attack the Papitalai Plantation from the east while the 2nd Squadron, 12th Cavalry, moved on Papitalai Mission. The 5th Cavalry captured Porlaka without opposition and crossed Lemondrol Creek in canvas and rubber boats.
The presence of a coral reef meant that conventional landing craft could not be used for the landing at Papitalai Mission. The five tracked landing craft (one combat and four cargo-carrying) set out from Hyane Harbour to Salami Plantation, but the road was so bad that only the combat vehicle and one of the cargo carriers were available in time. The attack nonetheless started, preceded by an air attack and artillery bombardment by the 271st Field Artillery Battalion. The combat LVT fired 24 M8 4.5-in (114.3-mm) rockets. Return fire was received from Japanese mortars and machine guns, and also one 75-mm (2.95-in) howitzer. The men of the first US assault wave had to hold alone in the face of fire from Japanese bunkers for 45 minutes until the LVTs returned with the men of the next wave. Later, they fought off a counterattack by about 30 Japanese. Joined by a third LVT which had eventually managed to make it to Salami, the LVTs made 16 trips across the harbour before the fall of darkness forced a halt, and by this time they had delivered part of the 2nd Squadron, 12th Cavalry, together with rations, water and ammunition, and evacuated the dead and wounded.
Ezaki reported the US attack on Papitalai Mission to the the 8th Area Army in Rabaul, promising a night counterattack on the position, but in he event no attack was made. The Japanese withdrew, and no further message was received from Ezaki.
The task of silencing the Japanese guns guarding Seeadler Harbour fell to Rear Admiral V. A. C. Crutchley’s Task Force 74, comprising the Australian heavy cruiser Shropshire, US light cruisers Phoenix and Nashville, and US destroyers Bache, Beale, Daly and Hutchins. TF74’s ships bombarded Hauwei island for one hour on 4 March, but on 6 March the US destroyer Nicholson was hit by a Japanese shell fired from Hauwei. With minesweepers scheduled to attempt to enter Seeadler Harbour again on 8 March, Kinkaid ordered Crutchley to make another attempt, and during the afternoon of 7 March TF74 bombarded Hauwei, Ndrilo, Koruniat, Pityilu and northern Los Negros. Shropshire fired 64 8-in (203-mm) and 92 4-in (101.6-mm) rounds, while the US cruisers and destroyers expended 1,144 6-in (152-mm) and 5-in (127-mm) rounds. On the following day, two destroyers, two minesweepers, a medium landing craft outfitted as a floating anti-aircraft vessel and six medium landing craft carrying trucks and supplies entered Seeadler Harbour without being engaged by Japanese artillery. This cleared the way for the 2nd Cavalry Brigade of the 1st Cavalry Division to land at Salmi on 9 March.
By 7 March, the 'Seabee' unit had the Momote airfield ready for operation, and indeed artillery spotting aircraft had already begun to use the strip on the previous day. Guided by a B-25, 12 Curtiss P-40 Kittyhawk fighter-bombers of No. 76 Squadron, RAAF, arrived from Kiriwina via Finschhafen on 9 March, the squadron’s other 12 aircraft following the next day. They were joined by the ground crew of No. 77 Squadron, RAAF, which had arrived by tank landing ship on 6 March. The rest of No. 73 Wing, RAAF, arrived during the next two weeks, this including the Kittyhawk aircraft of No. 77 Squadron and Supermarine Spitfire fighters of No. 79 Squadron. Operations began on 10 March, and henceforth ships and ground units in the Admiralty islands group had air support just minutes away.
The ANGAU detachment reached the town of Mokerang on 9 March and found 50 inhabitants. The men of the detachment was relieved to find islanders had not been deliberately ill-treated by the Japanese, but in their retreat the latter had stripped their gardens of food, leaving the civilian population hungry, so ANGAU arranged for them to be provisioned by the Americans.
By this time operations on Los Negros had now reached the mopping-up stage, but an estimated 2,700 Japanese troops remained on Manus island. Swift decided to land Brigadier General Verne D. Mudge’s 2nd Cavalry Brigade at Lugos Mission, to the west of Lorengau. Known to be heavily fortified, Lorengau was an important objective as it possessed an airfield, and four roads converged there. As a preliminary, the 302nd Cavalry Reconnaissance Troop was ordered to locate sites from which artillery could cover landings on Manus. Three patrols were sent out by LCVP on 11 March. The first found Bear Point on Manus free of Japanese but lacking sites for artillery emplacements. The second scouted the Butjo Luo islands, which they found apparently unoccupied and with good sites on the northern island.
The third patrol, of 25 officers and men of the 302nd Cavalry Reconnaissance Troop, two officers from the 99th Field Artillery Battalion, with Warrant Officer 2nd Class A. L. Robinson of ANGAU and Kaihu, a native of Mokerang, as guides, set out for Hauwei in an LCVP, escorted by PT-329, one of the PT boats now operating from the tender Oyster Bay in Seeadler Harbour. As the patrol moved ashore, Major Carter S. Vaden spotted a well camouflaged bunker and threw two hand grenades into it. When they exploded, concealed Japanese mortars and machine guns opened fire on the patrol and the craft offshore. The PT-boat was hit, its commander being wounded, and the boat withdrew. The LCVP headed toward the shore, where it picked up five men, including Robinson and Kaihu, backed off the beach and headed out to sea, but then sighted another group on the beach. The boat headed back to collect them, despite her commander being wounded, and succeeded in this task. As the boat backed off the beach again, it was holed by a mortar round and began taking on water. Meanwhile the damaged PT-boat had reported events and a bomber was sent to investigate. Flying low, it spotted the men in the water, and another PT-boat was sent to the rescue, covered by the Australian destroyer Arunta. After three hours in the water, the LCVP’s survivors were picked up by the PT-boat. Eight Americans, including Vaden, had been killed and 15 wounded, including the entire LCVP crew. Kaihu was missing and Robinson was contemplating how he would break the news to his family when Kaihu walked in, having swum back to Los Negros.
Swift postponed the landing on Lugos and ordered the 2nd Squadron, 7th Cavalry, to capture Hauwei. Once again, Robinson acted as guide, notwithstanding severe sunburn from his time in the water during the previous day. The landing was covered by the destroyers Arunta, Bush, Stockton and Thorn; two rocket-firing LCVPs and the LCM (Flak), which fired 168 4.5-in (114.3-mm) rockets; the guns of the 61st Field Artillery Battalion on Los Negros; and six Kittyhawk fighter-bombers of No. 76 Squadron, which dropped 500-lb (227-kg) bombs. The assault was made from three cargo-carrying LVTs which, to reduce wear and tear, were towed across Seeadler Harbour by LCMs and cut loose for the final run in to shore.
Here the cavalrymen found bunkers which were both well sited and well constructed, with interlocking fields of fire covering all approaches, and carefully positioned snipers. The next morning an LCM brought over a medium tank, which the Japanese lacked the weapons to destroy, and the cavalrymen were able to overcome the defenders at a cost of eight killed and 46 wounded; 43 dead Japanese naval personnel were counted. The 61st and 271st Field Artillery Battalions were then moved to Hauwei, while the 99th Field Artillery Battalion established itself on Butjo Luto.
On 12 March there arrived a fourth convoy, this comprising six tank landing ships and the destroyers Flusser, Reid, Kalk, Gillespie, Hobby and Warramunga.
The attack on Manus began on 15 March. Before dawn, two troops of the 8th Cavalry, six cargo-carrying LVTs and the one combat LVT were loaded on board an LST for the 11-mile (18-km) passage across Seeadler Harbour from Salami. Beaches at Lugos, about 2.5 miles (4 km) to the west of Lorengau, were chosen in preference to those nearer Lorengau, which were known to be heavily defended. The US destroyers Gillespie, Hobby, Kalk and Reid shelled the area with their 5-in (127-mm) guns; the two rocket-firing LCVPs, the LCM (Flak) and the combat LVT raked the shoreline with rockets; the artillery on Hauwei and Butjo Luo engaged targets; and 18 B-25 bombers of the 499th and 500th Bombardment Squadrons dropped 81 500-lb (227-kg) bombs and strafed the area.
The Japanese had evidently not expected a landing at Lugos, and their positions there were quickly overrun. The 1st Squadron, 8th Cavalry, then advanced to the east until it was stopped by a Japanese bunker complex on the edge of the Lorengau airstrip. An artillery barrage was brought down, followed by an air attack by Kittyhawk fighter-bombers. The cavalry then resumed the advance and occupied a ridge overlooking the airstrip without opposition. Meanwhile the 7th Cavalry had been landed at Lugos from the LST on its second trip, and assumed responsibility for defence of the area, freeing the 2nd Squadron, 8th Cavalry, to join the attack on Lorengau. The first attempt to capture the airstrip was checked by a Japanese bunker complex. A second attempt on 17 March, reinforced by the 1st Squadron, 7th Cavalry, supplemented by tanks, made good progress, and the advance then resumed, with Lorengau itself falling on 18 March.
Despite the fact that they had seen considerable combat, the Americans had yet to locate the main Japanese force on Manus. Advancing inland toward Rossum, the 7th Cavalry found the main Japanese body on 20 March, and there followed six days of fighting before the 7th and 8th Cavalry reduced the entrenched Japanese positions in the Rossum area. As always, the Japanese bunkers, constructed of logs and packed earth, proved highly resistant to artillery fire.
As the Japanese on Los Negros ran out of food and ammunition, the fight became increasingly unequal, and a last stand by 50 Japanese in the Papitalai hills on 24 March marked the end of organised Japanese resistance on Los Negros. The end of organised resistance on Los Negros and Manus still left a number of outlying islands in Japanese hands. To minimise civilian casualties, the ANGAU quietly evacuated these islands in advance of the US operations. Pityilu was believed occupied by about 60 Japanese, and on 30 March the 1st Squadron, 7th Cavalry, was transported there from Lorengau by 10 LCMs towing seven LVTs. With the lessons of Hauwei in mind, the landing was covered by bombardment by destroyers, artillery, and two support landing craft, as well as air attacks by Kittyhawk and Spitfire warplanes. The landing itself was unopposed, but the cavalrymen then encountered a strong Japanese position which was overcome with the aid of artillery and tanks. Some 59 Japanese were killed, while the Americans lost eight men killed and six wounded.
The same assault pattern was used on Ndrilo and Koruniat islands on 1 April, but the 1st Squadron, 12th Cavalry, found these two islands to be unoccupied. The last landing was that on Rambutyo island during 3 April by the 2nd Squadron, 12th Cavalry. This time, six LCMs and six LCVPs were used instead of the LVTs. As a result, the first waves grounded on a reef and troopers had to wade ashore through the surf. Fortunately for them there was no opposition. The Japanese, hiding in the interior, were eventually located by the ANGAU and 30 Japanese were killed and five captured. Patrols continued hunting for Japanese throughout the islands as, increasingly, the cavalry pursued sightings by the native population. On Los Negros, the 302nd Cavalry Reconnaissance Troop killed 48 and captured 15 Japanese during May. On Manus, some 586 Japanese dead were counted and 47 prisoners taken. Krueger officially declared the campaign over on 18 May.
Ultimately, it was air and naval superiority which made it possible for the Allies to make a major reinforcements of their strength on Los Negros, and from here Swift’s 1st Cavalry Division could then sweep to the west and overrun the islands. Though the campaign ended officially on 18 May, mopping-up operations lasted for a short time longer. The Allied success in 'Brewer' had strategic ramifications inasmuch as it completed the isolation of the major Japanese base at Rabaul that was the ultimate objective of the South-West Pacific Area command’s campaigns of 1942 and 1943. A major air and naval base was then developed in the Admiralty islands group, which thus became an important launching point for the campaigns of 1944 in the western Pacific.
The only other route toward the Japanese bases on New Britain and New Ireland had been closed on 20 March when Major General Harry Schmidt’s 4th Marine Division landed unopposed in 'Beefsteak' on Emirau and Mussau islands in the St Matthias islands group to the east of the Admiralty islands group, the effect being to trap Imamura’s 8th Area Army on New Ireland and the eastern end of New Britain, and Lieutenant General Harukichi Hyakutake’s 17th Army on Bougainville farther down the chain of the Solomon islands, where it was hotly engaged with Major General Oscar W. Griswold’s US XIII Corps.
At this time the Joint Strategic Survey Committee was advocating that 'the primary effort against Japan be made from the east across the central Pacific, with a view to the early seizure of the Formosa, Luzon, China coast area as a base to attack Japan', and that the South-West Pacific Area should support the primary effort with whatever resources could be spared for it. Strategic thinking in Washington began to change after the success of 'Brewer', however, and MacArthur capitalised on this fact by proposing a few days later that his forces should bypass Hansa Bay, scheduled for attack in late April 1944, and instead made the 580-mile (935-km) jump straight to Hollandia, this 'Reckless' operation isolating 40,000 Japanese troops along the north coast of New Guinea. The proposal was part of the far-reaching 'Reno IV' scheme which MacArthur submitted to Washington in early March 1944 through his chief-of-staff, Lieutenant General Richard K. Sutherland. This plan called for the South-West Pacific Area command to retain control of many of the resources of Halsey’s South Pacific Area command, which was about to wind up its operations, and also enjoy the support of some of Nimitz’s Central Pacific Area carrier task forces for the object of returning to Luzon in the Philippine islands group by January 1945. Nimitz objected that this would destroy the impetus of his central Pacific offensive, but the Joint Chiefs-of-Staff on 12 March issued a directive ordering MacArthur to press ahead along the northern coast of New Guinea to the Vogelkop peninsula in preparation for an invasion of Mindanao in the Philippine islands group during November 1944, and Nimitz to neutralise Truk in the centre of the Caroline islands group, capture the Mariana islands in mid-June, and seize the Palau islands group in mid-September to provide a base only 600 miles (965 km) to the east of Mindanao.
The strategic and operational importance of 'Brewer', which was by any standards an operational risk, is attested by the developments that were set in hand even even before the land operation had been completed. Discussions concerning the scope and nature of base development in the Admiralty islands group were held in early February between representatives of South-West Pacific Area and Halsey neighbouring South Pacific Area. The original intention had been for forces if the South-West Pacific Area to take the islands and construct the airbase, while the South Pacific Area would be responsible for the development of the naval base. Then the South Pacific Area indicated that it would not be able to supply troops or materials in the early stages, so it was decided that the South-West Pacific Area would also undertake the initial stages of naval base development.
Nimitz recommended to the Joint Chiefs-of-Staff that development and control of the base facilities be placed under the South Pacific Area by extending this command’s border westward to include the Admiralty islands group, and this angered MacArthur. Moreover, the South-West Pacific Area’s boundary could not be changed without Australian government approval. Nimitz’s proposal was eventually rejected by the Joint Chiefs-of-Staff, but not before MacArthur restricted access to the facilities to ships of Vice Admiral Thomas C. Kincaid’s US 7th Fleet and Admiral Sir Bruce Fraser’s British Pacific Fleet. Halsey was summoned to MacArthur’s headquarters in Brisbane on 3 March, and the two commanders then agreed to a compromise. Responsibility for the development of the base passed from Krueger’s 'Alamo' Force to Kinkaid’s Allied Naval Forces on 18 May, and while it was also proposed that control would ultimately pass to the South Pacific Area command it never did so.
Momote airfield was found to have been constructed on a coral sub-base covered with coconut palm humus, over which the Japanese had laid a thin layer of coral and coral sand. This was incapable of surviving heavy use, so 40th Naval Construction Battalion, 8th Engineer Squadron, and Shore Battalion of the 592nd EBSR had to strip away the humus and lay a new coral surface. Just 3,600 ft (1100 m) of runway was sufficient for the Kittyhawk and Spitfire tactical fighters, but the runway had been lengthened to 7,800 ft (2375 m) by a time late in April. This allowed the B-24 heavy bombers of Colonel Thomas C. Musgrave’s (from 21 April Colonel Joseph E. Reddoch’s) 5th Bombardment Group to arrive on 18 April 1944, and the group flew its first mission two days later against Woleai.
Plans called for a second airfield to be built at Salami Plantation, but surveys then revealed that the site was unsuitable and a new site was found in a coconut plantation near Mokerang. While the 46th Naval Construction Battalion cleared an access road, the 836th Engineer Aviation Battalion constructed the runway, and the 104th and 46th Naval Construction Battalions built the taxiways and dispersal areas. As at Momote, the humus had to be removed to reach the coral substrate, which was then graded and compacted. In places the coral was so hard explosives had to be used. The work required the clearing of 1,100 acres (4445 hectares) and the removal of 18,000 coconut trees.The B-24 bombers of Colonel Robert F. Burnham’s 307th Bombardment Group arrived on 21 April 1944, and this group later participated in raids on Biak and supported the Battle of Biak in May.
A base to provide repair and overhaul facilities for carrierborne fighters was constructed by the 78th Naval Construction Battalion on Ponam island. As half of the area was swamp, coral was blasted and dredged from the sea and used as landfill. Another facility for carrierborne aircraft was built on Pityilu island by the 71st Naval Construction Battalion in May and June 1944, along with accommodation for 2,500 men. The eastern end of Pityilu island was cleared and a fleet recreation centre, which could accommodate up to 10,000 men at a time, was constructed.
Construction of the naval base on Los Negros island was the responsibility of the 11th, 58th and 71st Battalions of the 2nd Naval Construction Regiment. Work included bulk storage at Papitalai for some 68,000 tons of fuel oil, 14,000 tons of distillate, 10,000 tons of aircraft fuel, and 30,000 tons of vehicle fuel, a 500-bed evacuation hospital, two wharves each able to accommodate Liberty ships, 24 warehouses, and 83 administration buildings in Quonset huts. At Lombrum Point, the 'Seabee' personnel built a seaplane repair base, a ship repair base, and a landing craft repair base. A 250-ton pontoon dry dock was provided for the servicing of landing craft.
The development of facilities on Manus island was the responsibility of the 35th, 44th and 57th Battalions of the 5th Naval Construction Regiment, which arrived in mid-April. These units erected or created 128 storage buildings, 50 680-cu ft (19.26-m³) refrigerators, and a water system to supply 4 million US gal (15.1416 million litres) per day. Two sub-systems were developed, one using streams in the Lombrum area to supplied 2.7 million US gal (10,221 million litres) per day, and another for outlying areas using wells to produce 850,000 US gal (3.2176 litres) per day. The system included water treatment plants, reservoirs, and pipes. All construction work had been completed by April 1945, and the base remaining in use until the end of World War II.
In his final report on the campaign, Krueger reported that 3,280 Japanese dead had been counted and 75 had been captured. Perhaps 1,100 more were missing. The US casualties were 326 killed, 1,189 wounded, and four missing. Some 1,625 Americans had been evacuated for all causes, including wounds and illness. One Australian had been wounded. The ANGAU reported one native had been killed and one wounded in action, three killed by the Japanese, and 20 accidentally killed and 34 wounded by air, artillery and naval bombardment.
In overall terms, the importance of the Admiralty islands group to the Allied cause was enormous. Their capture saved more lives than it cost by obviating the need to capture Truk, Kavieng, Rabaul and Hansa Bay, in the process speeding the Allied advance by several months. As an airbase, the value of the Admiralty islands group was great, for aircraft based on the islands could range over Truk, Wewak and beyond. As a naval base, the island group’s value was still greater as it allowed the creation of a fleet anchorage with major facilities.
For the Japanese, the loss of the Admiralty islands group meant the loss of their outpost line in the south-eastern sector of their defensive perimeter. The Imperial General Headquarters now ordered the preparation of a new defensive line in western New Guinea. The Admiralty islands operation also indicated the Allies were becoming more ambitious and might bypass Hansa Bay. Accordingly, the 18th Army in New Guinea was also ordered to prepare the defence of Aitape and Wewak.