Acting on reports from airmen that there were no signs of enemy activity and the Admiralty Islands had possibly been evacuated, General Douglas MacArthur accelerated his timetable and ordered a reconnaissance in force of the islands. The campaign began on 29 February 1944 when a small force was landed on a beach on Los Negros Island. By landing on a small beach where the Japanese did not anticipate a landing attempt being made, the force achieved tactical surprise, but the islands proved to be far from unoccupied. A furious battle developed for control of the Admiralty Islands that was fought out on the islands, in the surrounding waters, and in the air above.
In the end, Allied air and naval superiority allowed the Allies to heavily reinforce their position on Los Negros. The 1st Cavalry Division was then able to overrun the islands. The campaign officially ended on 18 May 1944. The Allied victory completed the isolation of the major Japanese base at Rabaul that was the ultimate objective of the Allied campaigns of 1942 and 1943. A major air and naval base was developed in the Admiralty Islands that became an important launching point for the campaigns of 1944.
The invasion of the Admiralty Islands, codenamed Operation BREWER, was scheduled for 1 April 1944. Forces assigned included the 1st Cavalry Division; No. 73 Wing Royal Australian Air Force (RAAF), providing close air support; the 592nd Engineer Boat and Shore Regiment (EBSR); the US Marines' 1st Amphibious Tractor Battalion; and US Naval Construction Battalions ("Seabees") to build the naval base — a total of 45,000 personnel.
Three B-25 Mitchell bombers flew low over Los Negros on 23 February 1944. The airmen reported that there were no signs of enemy activity and the islands had been evacuated. Lieutenant General George Kenney, the commander of Allied Air Forces in MacArthur's South West Pacific Area (SWPA), went to MacArthur and proposed that the unoccupied islands be quickly taken by a small force. According to Kenney: "The General listened for a while, paced back and forth as I kept talking, nodded occasionally, then suddenly stopped and said: That will put the cork in the bottle".
Orders went out on 24 February 1944 for a reinforced squadron of the 1st Cavalry Division to carry out a reconnaissance in force in just five days time. If the Admiralty Islands were indeed evacuated, they would be occupied and a base developed. If the enemy was unexpectedly strong, then the force could be withdrawn. General MacArthur and Vice Admiral Thomas C. Kinkaid, the commander of Allied Naval Forces, would be on hand to make the decision but otherwise they delegated command to Rear Admiral William Fechteler, the commander of Amphibious Group 8. To accommodate them, the light cruiser USS Phoenix was ordered to sea. At the time it was in Brisbane, with over 300 of its crew on shore leave. Trucks with bull horns broadcast the code word recalling the crew.
Task Force BREWER Assault Echelon Units
Brigadier General William C. Chase
|Source: Krueger, Walter, Report on BREWER Operation, 2 August 1944, AWM54 519/1/12|
In order to achieve surprise, and to reach the Admiralty Islands in just five days, High speed transports (APDs) were required. The Landing Ships, Tank (LSTs) were too slow to make the required distance in the time. Only three APDs were available: USS Brooks, Humphreys and Sands. Each could accommodate 170 men. The remaining troops were carried on nine destroyers: USS Bush, Drayton, Flusser, Mahan, Reid, Smith, Stevenson, Stockton and Welles. Between them, the destroyers and APDs carried 1,026 troops.
This force was commanded by Brigadier General William C. Chase, commander of the 1st Brigade, 1st Cavalry Division. It included the three rifle troops and the heavy weapons troop of the 2d Squadron, 5th Cavalry; a platoon from Battery B, 99th Field Artillery Battalion with two 75 mm 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 native population, some 13,000 of whom lived in the Admiralty Islands.
Once the decision to remain was known, a follow-up force with the rest of the 5th Cavalry and 99th Field Artillery Battalion, 40th Naval Construction Battalion and 2,500 measurement tons of stores would depart from Finschhafen in six LSTs, each towing an LCM of Company E, 592nd EBSR. When an aide expressed concern over assigning such a hazardous mission to a unit without combat experience, General MacArthur recalled how the 5th Cavalry had fought alongside his father's troops in the campaign against Geronimo. "They'd fight then ," he said, "and they'll fight now.
Task Force BREWER Supporting Echelon Units
Colonel Hugh Hoffman
|Source: Krueger, Walter, Report on BREWER Operation, 2 August 1944, AWM54 519/1/12|
The 51st Transport Regiment had constructed an airstrip on Lorengau and commenced another, known as Momote Airstrip, at the Momote Plantation on Los Negros. Lorengau was used as a staging point for aircraft moving between Rabaul and airstrips in North East New Guinea. The importance of the Admiralty Islands to the Japanese increased as the result of Allied advances in New Guinea and New Britain which blocked off other air routes. Reinforcements were sent from Palau in December 1943 but they were attacked by submarines and forced to turn back. Two infantry battalions were sent from Rabaul in January 1943. Although attacked en route by Allied aircraft, they made it safely. By February, both airstrips were unserviceable and the antiaircraft guns were silent in order to conserve ammunition and conceal their positions. Ezaki had ordered his men to neither move nor fire in daylight.
The chosen landing site 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 wide. "Since the whole operation was a gamble anyway," Samuel Eliot Morison noted, "one might as well be consistent. The gamble paid off. The Japanese had not anticipated a landing at this point and the bulk of their forces were concentrated on the other side of the island to defend the beaches on Seeadler Harbour.
The weather on 29 February 1944 was overcast with a low cloud ceiling that prevented most of the planned air strike. Only three B-24 Liberators and nine B-25 Mitchells found the target. The naval bombardment was therefore extended for another 15 minutes.
Each APD lowered four LCPRs. Each carried its maximum load of 37 men, who boarded them by climbing down cargo nets over the APDs' sides. The unarmoured LCPRs were still used by the APDs because their davits had not been strengthened to carry the heavier, armoured LCVP.
The first wave landed without casualties at 0817, but once the bombardment lifted the Japanese emerged from their dugouts and machine guns and shore batteries began to open up. The landing craft, on returning, came under crossfire from enemy machine guns on both sides of the harbour. The fire became so heavy that the second wave was forced to reverse course until the enemy fire was suppressed by destroyers. The third and fourth waves also came under fire. A correspondent from Yank, the Army Weekly described the scene:
Four of the twelve LCPRs had been damaged. Three were soon repaired, but they could not be risked further, for without the LCPRs, the reconnaissance force could not be evacuated. The emergency plan provided for an APD to enter the harbour and take troops off from a jetty but this would clearly be a desperate measure indeed. Over the next four hours, the boats continued to make trips to the beach, but only when it was believed that the destroyers had suppressed the enemy guns. Heavy rain made it safer by reducing visibility. The last destroyer was unloaded at 1250. By this time the navy had lost two men dead and three wounded.
For the moment it was safer ashore. The cavalrymen overran the airstrip. Sporadic opposition allowed them to set up the antiaircraft machine guns on the beach, unload supplies, and patrol inland. Two soldiers were killed and three wounded. At 1600, General MacArthur and Admiral Kinkaid came ashore. The general inspected the position. A lieutenant warned him that a Japanese sniper had been killed in the vicinity just a few minutes before. "That's the best thing to do with them," the General replied, and continued on. MacArthur made the decision to stay, ordering Chase to hold his position until the follow-up force arrived. He then returned to Phoenix. Fechteler's force departed at 1729, the transports having unloaded and most of the bombardment force having exhausted its ammunition. Bush and Stockton remained to provide on-call naval gunfire support.
Chase pulled his troops back into a tight perimeter. There was no barbed wire, so the whole area had to be covered. The ground was hard coral, which was good for airbase construction but made it difficult to dig foxholes. The twelve .50 calibre machine guns were positioned in the front line. There was fighting throughout the night as small groups of Japanese attempted to infiltrate the position.
An airdrop of ammunition was requested. A break in the weather allowed three B-25s of the US 38th Bomb Group to drop supplies at 0830. Four B-17s of the 375th Troop Carrier Group each dropped three tons of supplies, including blood plasma, ammunition, hand grenades and barbed wire. Some of the ammunition fell beyond the perimeter but for some reason men who moved out to retrieve it were not fired upon.
The Japanese were not expected to make another effort until dark but at around 1600 a Japanese patrol was discovered that had somehow managed to infiltrate the perimeter in broad daylight and penetrate to within of General Chase's command post. A sniper opened fire on the command post and fire was directed at the patrol. Major Julio Chiaramonte, S-2 of the task force, set out with four men to silence the sniper. As his party closed in on the position, there were a series of explosions. Three of the Japanese had committed suicide with hand grenades, while another had committed seppuku with his sword. Fifteen dead officers and sergeants were counted, including Captain Baba, the commander of the Japanese battalion which made the attack the preceding night. The Japanese launched another attack on the perimeter at 1700 but could make little progress in the face of American firepower.
The next morning saw the arrival of the follow-up force, six LSTs, each towing an LCM, escorted by the destroyers USS Mullany and Ammen and HMAS Warramunga and destroyer minesweepers USS Hamilton and Long. They entered Hyane Harbour and beached, coming under mortar fire as they did so. LST 202, manned by a United States Coast Guard crew, replied with 3 inch and Bofors 40 mm guns.
The LSTs were unloaded over the next seven hours. In the process, ammunition, construction equipment and stores piled up. To obtain a larger perimeter that could accommodate a proper dispersal of stores, General Chase ordered an attack to expand the perimeter. An air strike was requested. B-25s of the US 345th Bomb Group were intercepted by an estimated fifteen Japanese fighters. These were driven off by eight escorting P-47 Thunderbolt fighters, which claimed eight Japanese aircraft shot down. Two B-17s of the US 69th Troop Carrier Squadron on a supply dropping run were also attacked, and claimed to have shot one of their attackers down. Regrettably, two of the four B-25 squadrons dropped bombs in areas occupied by American troops, two of whom were killed and four wounded before the US 12th Air Liaison Party could correct the error. Both squadrons of the 5th Cavalry attacked at 1500. All objectives were taken and a new, larger defensive perimeter was prepared.
The 40th Naval Construction Battalion had landed expecting to work on Momote airstrip. Instead, they were ordered to use their equipment to clear fields of fire and construct fortifications, and were given a section of the perimeter to defend. Six trenches were dug out by a bulldozer and ten men stationed in each. Their ditch digger scooped out trench which formed a secondary line of defence. The airstrip's revetments were transformed into heavy machine gun posts.
The two destroyer minesweepers were supposed to sweep the entrance to Seeadler Harbour between Hauwei and Ndrillo Islands but fire from at least one Japanese 4 inch gun on Hauwei Island prevented them from entering the harbour. Captain Emile Dechaineux, the senior officer afloat, brought Ammen, Bush, Mullany and Warramunga around and bombarded the island. The Japanese guns ceased fire but came alive again when another attempt was made to sweep the channel. Dechaineux then called off the effort, ordering the minesweepers to join him. The destroyers bombarded the Japanese guns covering the entrance to Hyane Harbour to allow the LSTs to leave unmolested. One LST left with between 20 and 30 truckloads of stores still on board. The LSTs did not wish to remain after dark as a Japanese attack was expected. Dechaineux escorted them part of the way until he received an order from Rear Admiral Daniel E. Barbey, the commander of VII Amphibious Force, for Ammen, Mullany, Warramunga and Welles to remain off Los Negros. Ammen and Mullany bombarded 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.
General Krueger was gravely concerned about the seriousness of the situation on Los Negros. In response to urgent request from General Chase, Krueger arranged with Admiral Barbey for the movement of the rest of the 1st Cavalry Division to be expedited. At Krueger's request, the 2nd Squadron, 7th Cavalry would travel in the three APDs. Other units would arrive on 6 and 9 March instead of 9 and 16 March. Krueger realised that Hyane harbour was too small to support the entire division, but there were good beaches around Salami Plantation on the western shore of Los Negros. In order to use them, and to permit a shore-to-shore operation against Manus from Los Negros, Seeadler Harbour would have to be opened up.
From the Japanese perspective, the battle was not going too well either. The Japanese had expected a landing on Seeadler Harbour, this being the logical American objective, and had concentrated their forces around the Lorengau aerodrome. The defence of the Momote airstrip and Hyane harbour was the responsibility of Baba Force, built around Captain Baba's 1st Battalion, 229th Infantry Regiment. Colonel Ezaki ordered Baba to attack the beachhead but a suspicion that the Hyane Harbour landing was a diversion, coupled with false reports of enemy activity at Salami had him retain the 2nd (Iwakami) Battalion of the 1st Independent Infantry Regiment there instead of sending it to assist Baba Force. By 2 March, Ezaki had resolved to attack the Hyane beachhead with his whole force. The difficulties imposed by the terrain, and disruption by American artillery and Allied naval gunfire forced a postponement of the attack to the night of 3 March.
At 2100 a lone Japanese plane dropped eight bombs, cutting telephone wires. Once it had departed, yellow flares went up and a Japanese ground attack was launched, supported by mortar fire. Offshore, Dechaineux' destroyers came under attack from four Betty bombers. The 1st Squadron, 5th Cavalry's position was attacked by about two reinforced platoons, which were met by a hail of automatic weapons and mortar fire. The heavy jungle in this sector permitted some infiltration but the Japanese force was not strong enough to overrun the 1st Squadron.
The main Japanese attack was delivered by the 2nd Battalion, 1st Independent Mixed Regiment from the direction of the native skidway, together with detachments from the Porlaka area, and fell on the 2nd Squadron, 5th Cavalry. The troopers noticed a change in Japanese tactics. Instead of infiltrating silently, they 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 Americans' automatic weapons, including several .30 water-cooled Browning heavy machine guns, but the advance continued. The guns of the 211th Coast Artillery (AA) Battalion and 99th Field Artillery Battalion fired through the night, attempting to break up the Japanese attack from Porlaka. Shortly after midnight, Japanese barges attempted to cross Hyane harbour but were engaged by the anti-aircraft guns and did not reach the American positions. A Bofors 40 mm gun position was captured by the Japanese, who in turn were driven off by the Seabees. Manning the heavy Browning machineguns, the 5th Cavalry's gunners piled up the Japanese dead until the guns had to be moved to get clear fields of fire. One of the Browning guns that held the position was later left in its place, as a monument.
Sergeant Troy McGill, occupied a revetment with his squad of eight men. All members of the squad were killed or wounded except McGill and another man, whom he ordered to return to fall back next revetment. McGill fired his rifle until it jammed, then clubbed the Japanese with it until he was killed. He was posthumously awarded the Medal of Honor.
By dawn, the attack had subsided. Over 750 Japanese dead were counted in and around the American positions. No prisoners were taken. American casualties were 61 dead, and 244 wounded, including 9 dead and 38 wounded Seabees. The 2d Squadron, 5th Cavalry and the 40th Naval Construction Battalion received Presidential Unit Citations. General Chase called for an airdrop of ammunition, prodigious quantities of which had been expended during the night, and had Warramunga fire on the native skidway.
The morning of 4 March saw the arrival of the 2nd Squadron, 7th Cavalry, which relieved the 2nd Squadron, 5th Cavalry. The next day Major General Innis P. Swift, the commander of the 1st Cavalry Division, arrived on the Bush and assumed command. He ordered the 2nd Squadron, 7th Cavalry to attack across the native skidway. The 2nd Squadron, 5th Cavalry therefore went back into the line to relieve them. While the relief was taking place, the Japanese launched a daylight attack. This was repulsed by the cavalrymen, with the help of artillery and mortar fire, but the attack was delayed until late afternoon. It then ran into a Japanese minefield and by dawn the advance had only advanced as far as the skidway.
On the morning of 6 March, another convoy arrived at Hyane Harbour, five LSTs, each towing an LCM, with the 12th Cavalry and other units and equipment including five LVTs of the 592nd EBSR, three Stuart tanks of the 603rd Tank Company, and twelve 105mm howitzers of the 271st Field Artillery Battalion. The 12th Cavalry was ordered to the follow the 2nd Squadron, 7th Cavalry in its advance to the north, and to capture the Salami Plantation. The road to Salami was little more than a muddy track in which vehicles soon became bogged. The Japanese obstructed the route with ditches, felled trees, snipers, and booby traps. WO2 R. J. Booker of ANGAU used his local knowledge to guide the 12th Cavalry and the three tanks to Salami. Here the Japanese put up a fierce fight that lasted over an hour. The tanks fired canister shot shells 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. This therefore became the next objective. The 5th Cavalry would attack Papitalai Palantation from the east while the 2nd Squadron, 12th Cavalry would attack Papitalai Mission. The 5th Cavalry captured Porlaka without opposition and crossed Lemondrol Creek in canvas and rubber boats. A patrol under Captain William C. Cornelius fought with an estimated 50 Japanese, who ultimately withdrew. Captain Cornelius, who was credited with killing four, was severely wounded and died the next day. He was posthumously awarded the Distinguished Service Cross.
Because of the coral reef, conventional landing craft could not be used for the landing at Papitalai Mission. The five LVTs, one a combat type and the other four cargo carrying, set out from Hyane Harbour to Salami Platation but the road was so bad that only one combat and one cargo LVT were available in time. The attack went ahead anyway, preceded by an airstrike and artillery bombardment by the 271st Field Artillery Battalion. The combat LVT fired 24 M8 4.5 inch Rockets. Return fire was received from Japanese mortars, machine guns and a 75mm howitzer. The first wave had to hold alone in the face of fire from Japanese bunkers for 45 minutes until the LVTs returned with the next wave. later, they fought off a counterattack by about 30 Japanese troops. Joined by a third LVT which had eventually managed to make it to Salami, the LVTs made 16 trips across the harbour before nightfall curtailed operations, transporting part of the 2nd Squadron, 12th Cavalry, along with rations, water and ammunition, and evacuating the dead and wounded.
Colonel Ezaki reported the American attack on Papitalai Mission to the Eighth Area Army in Rabaul, promising a night counterattack on the position; but no attack was delivered. The Japanese withdrew, and no further messages were ever received from Colonel Ezaki.
The task of silencing the Japanese guns guarding Seeadler Harbour fell to Rear Admiral Victor Crutchley's Task Force 74, consisting of the heavy cruiser HMAS Shropshire, light cruisers USS Phoenix and Nashville, and destroyers USS Bache, Beale, Daly and Hutchins. They bombarded Hauwei Island for an hour on 4 March but on 6 March USS Nicholson was struck by a Japanese shell fired from Hauwei. With minesweepers scheduled to attempt to enter Seeadler Harbour again on 8 March, Admiral Kinkaid ordered Crutchley to try again. On the afternoon of 7 March, Task Force 74 bombarded Hauwei, Ndrillo, Koruniat, Pityilu and northern Los Negros. Shropshire fired 64 8 inch and 92 4 inch shells, while the American cruisers and destroyers expended 1,144 5 inch and 6 inch shells. The next day, two destroyers, two minesweepers, an LCM (flak) and six LCMs carrying trucks and supplies entered the Seeadler Harbour without being fired upon. This cleared the way for the 2nd Brigade, 1st Cavalry Division to land at Salmi on 9 March.
By 7 March, the Seabees had the Momote airfield ready. Artillery spotting aircraft began operating from the strip on 6 March and a B-25 Mitchell made an emergency landing the next day. Guided by a B-25 Mitchell, twelve P-40 Kittyhawks of No. 76 Squadron RAAF arrived from Kiriwina via Finschhafen on 9 March, the remaining twelve aircraft of the squadron following the next day. They were joined by the ground crew of No. 77 Squadron RAAF, which had arrived by LST on 6 March. The rest of No. 73 Wing RAAF arrived over the next two weeks, including the Kittyhawks of No. 77 Squadron RAAF and Supermarine Spitfires of No. 79 Squadron RAAF. Operations began on 10 March and henceforth ships and ground units in the Admiralties had air support just minutes away.
The ANGAU Detachment reached the town of Mokerang on 9 March and found fifty of the inhabitants. The ANGAU Detachment was relieved to find that the islanders had not been deliberately ill-treated by the Japanese. The retreating Japanese had stripped their gardens of food, leaving the civilian population hungry, so ANGAU arranged for them to be rationed by the Americans.
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 up, both on the patrol and the craft offshore. The PT Boat, hit and with its commander wounded, withdrew. The LCVP headed toward the shore where it picked up five men, including Robinson and Kaihu. The LCVP retracted and headed out to sea but then sighted another group on the beach. The LCVP headed back in to pick them up, which it did despite its commander being wounded. As it backed off the beach it was hit and holed by a mortar round, and began to sink. All on board donned life jackets before the LCVP sank beneath them. Meanwhile the damaged PT Boat had reported what had happened 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 destroyer HMAS Arunta. After three hours in the water, the survivors were picked up by the PT boat. Eight Americans, including Major Vaden, had been killed and fifteen 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 swam back to Los Negros.
General Swift postponed the landing on Lugos and ordered the 2nd Squadron, 7th Cavalry to capture Hauwei. Once again, Robinson acted as guide, not withstanding severe sunburn from his time in the water the previous day. The landing was covered by the destroyers Arunta, Bush, Stockton and Thorn; a pair of rocket-firing LCVPs and the LCM (flak), which fired 168 4.5 inch rockets; the guns of the 61st Field Artillery Battalion on Los Negros; and six Kittyhawks of No. 76 Squadron dropped 500 pound bombs. The assault was made from three cargo-carrying LVTs. To save wear and tear, they were towed across Seeadler Harbour by LCMs and cut loose for the final run in to shore. The cavalrymen found well constructed and sited bunkers with interlocking fields of fire covering all approaches, and deadly accurate snipers. The next morning an LCM brought over a medium tank, for which the Japanese had no answer, and the cavalrymen were able to overcome the defenders at a cost of 8 killed and 46 wounded; 43 dead Japanese naval personnel were counted. The 61st and 27st Field Artillery Battalions moved to Hauwei, while the 99th established itself on Butjo Luto.
The attack on Manus got underway on 15 March. Before dawn, two troops of the 8th Cavalry, six cargo carrying LVTs and the combat LVT were loaded on board an LST for the 18 km trip across Seeadler Harbour from Salami. Beaches at Lugos, about 4 km west of Lorengau were chosen in preference to those nearer Lorengau, which were known to be heavily defended. The destroyers USS Gillespie, Hobby, Kalk and Reid bombarded the area with their 5 inch guns; the two rocket 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-25s of the 499th and 500th Bombardments Squadrons dropped 81 500 pound 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 eastward 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 airstrike by Kittyhawks with 500 pound bombs. The cavalry resumed their advance and occupied a ridge overlooking the airstrip without opposition. In the meantime, the 7th cavalry had been landed at Lugos from the LST on its second trip and took over the 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 an enemy bunker complex. A second attempt on 17 March, reinforced by the 1st Squadron, 7th cavalry and tanks, made good progress. The advance then resumed, with Lorengau itself falling on 18 March.
Although there had been plenty of fighting, the main Japanese force on Manus had not been located. Advancing inland towards Rossum, the 7th Cavalry found it on 20 March. Six days of fighting around Rossun were required before the 7th and 8th Cavalry reduced the entrenched Japanese positions there. The Japanese bunkers, actually log and earth pillboxes, proved resistant to artillery fire.
The end of organised resistance on Los Negros and Manus still left a number of islands in Japanese hands. To minimise civilian casualties, ANGAU quietly evacuated these islands in advance of the American operations.
Pitylu was believed occupied by about 60 Japanese. On 30 March the 1st Squadron, 7th Cavalry was transported there from Lorengau by 10 LCMs towing 7 LVTs. With the lessons of Hauwei in mind, the landing was covered by bombardment by destroyers, artillery, and two Landing Craft Support, plus an air strike by Kittyhawks and Spitfires. The landing was unopposed, but a strong Japanese position was encountered which was overcome with the aid of artillery and tanks. Some 59 Japanese were killed compared with 8 Americans killed and 6 wounded.
The same treatment was given to Ndrilo and Koruniat on 1 April but the 1st Squadron, 12th Cavalry found them unoccupied. This was notable for being the only amphibious operation of the war carried out in dugout canoes.
The final landing was on Rambutyo on 3 April by the 2nd Squadron, 12th Cavalry. This time, 6 LCMs and 6 LCVPs were used instead of the LVTs. The result was that the first waves grounded on a reef and the cavalry had to wade ashore through the surf. Fortunately, there was no opposition. The Japanese, hiding in the interior, were eventually located by ANGAU and 30 Japanese were killed and 5 captured.
Patrols continued hunting for Japanese throughout the islands. Increasingly, the cavalry followed up sightings reported by the natives. 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. General Krueger officially declared the campaign over on 18 May.
Admiral Chester W. Nimitz then recommended to the Joint Chiefs of Staff that development and control of the base facilities be placed under SOPAC by extending its border westward to include the Admiralties. MacArthur was furious; the borders of SWPA could not be changed without the consent of the Australian government. Nimitz' proposal was eventually turned down by the Joint Chiefs but not before MacArthur restricted access to the facilities to ships of the United States Seventh Fleet and British Pacific Fleet. Halsey was summoned to MacArthur's headquarters in Brisbane on 3 March 1944, and the two agreed to a compromise. Responsibility for the development of the base passed from Krueger's ALAMO Force to the Kinkaid's Allied Naval Forces on 18 May 1944. It was proposed that control would ultimately pass to SOPAC but it never did.
Plans called for a second aerodrome at Salami Plantation, but surveys 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 subgrade, which was then graded and compacted. In places the coral was so hard that explosives had to be used. The work required the clearing of and the removal of 18,000 coconut trees. The B-24 Liberators of the 307th Bombardment Group (the "Long Rangers") arrived on 21 April 1944, They participated in raids on Biak and supported the Battle of Biak in May.
A fighter base to provide repair and overhaul facilities for aircraft carrier aircraft was constructed by the 78th Naval Construction Battalion on Ponam Island. As half of the work area was swamp, coral was blasted and dredged from the ocean bed and used as landfill. Another facility for carrier aircraft was built on Pitylu by the 71st Naval Construction Battalion in May and June 1944, along with accommodation for 2,500 men. The eastern end of Pitylu was cleared and a fleet recreation centre was built that could accommodate up to 10,000 men at a time.
Development of facilities on Manus was taken in hand by the 5th Naval Construction Regiment, with the 35th, 44th and 57th Naval Construction Battalions, which arrived in mid-April. They erected 128 storage buildings and 50 refrigerators, each of capacity. A water supply system was developed to supply per day. Two sytems were developed, one using streams in the Lombrum area that supplied per day, and another for outlying areas that used wells to produce per day. The system included water treatment plants, reservoirs and pipes.
All construction work was completed by April 1945, with the base remaining in use until the end of the war.
A well-known rule of thumb is that an attacking force needs a 3:1 superiority to ensure success. In the opening stages of the battle of Los Negros, the ratio was more like 1:4. In the end the Allies won, "simply because," wrote Morison, "the United States and Australia dominated that stretch of ocean and the air over it. When queried about the naval support, General Chase replied that "they didn't support us; they saved our necks". Chase's own defensive tactics were also a vital factor. Chase was awarded the Bronze Star Medal for his part, as was MacArthur.
Allied commanders, and later historians, debated whether the Admiralty Islands Campaign was the bold action of a great commander or a reckless endeavour that courted disaster. Admiral Fechteler felt that "we're damn lucky we didn't get run off the island, and Admiral Barbey, for one, believed that the original plan would have resulted in overrunning the islands in short order with less casualties. It would certainly have been much less risky, but it is doubtful whether an assault on the well-defended beaches of Seeadler Harbour would have resulted in fewer casualties. Whereas, in accelerating both MacArthur and Nimitz' campaigns, it shortened the war by at least a month. Thus, in the final analysis, the campaign "had the great virtue of hastening victory while reducing the number of dead and wounded".
For the Japanese, the loss of the Admiralties meant the loss of their outpost line in the South Eastern Area. Imperial Headquarters now ordered the preparation of a new line in Western New Guinea. The Admiralties operation also indicated that the Allies were becoming more ambitious and might bypass Hansa Bay. Accordingly, the Eighteenth Army in New Guinea was ordered to prepare to defend Aitape and Wewak as well.