The end of the fighting in the Admiralty Islands

On 18 May 1944 General Walter Krueger, commander of the American Sixth Army – which operated in amphibious operations as Alamo Force – officially declared the operation in the Admiralty Islands over. The islands are the north-westernmost group of the Bismarck Archipelago, lying some 300 kilometres north-east of the coast of New Guinea. That same day responsibility for developing the captured bases passed from the army to the Allied naval forces of Vice Admiral Thomas Kinkaid. The campaign, which had begun on 29 February with a bold reconnaissance-in-force landing on Los Negros, thus formally lasted almost three months, although the heavy fighting took place in the first four weeks.

Popular chronologies state that on this day “the last Japanese resistance ceased” in the islands. This is a simplification: 18 May was the date on which the operation was administratively closed, not the day on which the last shot was fired. Organised resistance had already ended in late March, while scattered groups of Japanese soldiers went on hiding in the mountains and jungle of Manus long after 18 May.

From Los Negros to Lorengau

For the Allies the Admiralty Islands had two assets: airfields – Momote on Los Negros and Lorengau on Manus – and Seeadler Harbour, a vast, deep anchorage enclosed by a chain of islets, in which an entire fleet could anchor. Their capture was to close the ring around the great Japanese base at Rabaul on New Britain and complete Operation Cartwheel.

General Douglas MacArthur, persuaded by his airmen that the islands were almost empty, decided to bring the invasion forward by more than a month and to send in only a strong reconnaissance force at first. The landing on Los Negros on 29 February 1944 proved a risky gamble: the garrison under Colonel Yoshio Ezaki was many times larger than had been thought, and in night attacks it very nearly drove the cavalrymen into the sea. The beachhead was held thanks to the fire of destroyers and to reinforcements of the 1st Cavalry Division brought in quickly. Once the shores of Seeadler Harbour had been cleared, it was Manus’s turn: after a bloody landing on the islet of Hauwei, the Americans landed near Lugos on 15 March and began the capture of Manus; on 18 March they took the airfield and the settlement of Lorengau. The last organised resistance on Los Negros, the defence of the Papitalai hills by some 50 Japanese, ceased on 24 March, and on 25 March the cavalry reached the village of Rossum on Manus.

The smaller islands and the mopping-up

After the fall of their main positions the Japanese still held several islets around Seeadler Harbour and east of Los Negros. Australian officers of the Australian New Guinea Administrative Unit (ANGAU) had earlier quietly evacuated their inhabitants, to spare them casualties from artillery and air attack. On 30 March a troop of the 7th Cavalry Regiment landed on the islet of Pityilu, defended by about 60 Japanese; after a fight supported by artillery and tanks, 59 dead defenders were counted, while the Americans lost eight killed. On 1 April cavalrymen occupied the abandoned islets of Ndrilo and Koruniat – some of them in dugout canoes borrowed from the islanders, which is reckoned to have been the only American amphibious operation of its kind in the war. The last landing, on Rambutyo island on 3 April, met no resistance at the shore, but the Japanese hidden inland then had to be tracked down; according to American reports, some 30 were killed and five taken prisoner.

April and May were taken up with patrols. Cavalry detachments, increasingly guided by tips from the islanders, combed the mountains and rainforests of Manus and Los Negros. According to American reports, on Manus alone 586 Japanese dead were counted and 47 prisoners taken during this period, while on Los Negros the divisional reconnaissance unit (302nd Cavalry Reconnaissance Troop) killed 48 and captured 15 enemy soldiers in May. These were men exhausted by hunger and disease, often unarmed. A diary found on one of the dead describes how at the end of March a unit of about 300 men, without rations, wandered along mountain paths, abandoning weapons and equipment on the way, until its author noted that “there is nothing left but to live like the natives”.

18 May: the end of the operation

The Japanese garrison had ceased to exist as an organised force by April. Colonel Ezaki, who was both commander of the 51st Transport Regiment and of the whole defence of the islands, stopped reporting to headquarters in Rabaul after the first days of March; his subsequent fate is uncertain. According to Japanese sources, the last radio report from the islands reached headquarters on 1 May: some 1,050 army soldiers and 500 sailors remained there, without equipment or food, asking for orders. No help was possible any longer – the sea and the air around the Bismarck Archipelago belonged to the Allies.

In this situation Krueger’s announcement of 18 May 1944 was above all an organisational decision. General Innis P. Swift’s 1st Cavalry Division could begin preparing for its next tasks, and responsibility for the islands and for building the bases was taken over by the navy under Kinkaid, commander of the Seventh Fleet and of Allied Naval Forces in the South West Pacific Area. On 31 May the Japanese high command declared the entire garrison dead. Shattered groups of soldiers nevertheless remained on the islands, living on starch from sago palms and whatever they could find in the islanders’ gardens. Most were killed in the mopping-up or died of hunger and disease; a few, unaware that the war was over, hid in the mountains of Manus for several years after Japan’s surrender.

The toll

In his final report Krueger stated that over the whole campaign 3,280 Japanese dead had been counted and buried and 75 taken prisoner; he also estimated that the Japanese themselves had buried or hidden the bodies of about 1,100 more. These figures broadly agree with the Japanese estimate, according to which the garrison numbered some 3,800 men before the invasion. American losses, according to the same report, amounted to 326 killed, 1,189 wounded and four missing; some 1,600 men in all were evacuated because of wounds and sickness. One Australian was wounded. According to ANGAU, one islander was killed in the fighting, three were killed by the Japanese, and 20 were killed and 34 wounded accidentally – by Allied bombs, artillery and naval gunfire.

The ratio of losses – nearly ten Japanese dead for every American killed – became typical of the fighting in the Pacific in the months that followed: Japanese garrisons, cut off from supplies and brought up to believe that captivity was a disgrace, perished almost to a man.

The base at Seeadler Harbour

Even while the mopping-up was going on, the islands were being turned into one of the largest Allied bases in the Pacific. The navy’s construction battalions – the Seabees – and army engineers had to rebuild Momote airfield, whose Japanese surface could not withstand heavy traffic; by 18 May its runway was about 7,000 feet long, more than two kilometres. When it turned out that the airfield near Lorengau was unsuitable for expansion, a new one was built within a few weeks at Mokerang, ready on 21 April. From the second half of April B-24 bombers were already taking off from Momote to attack Japanese bases in the Carolines. Airstrips for carrier aircraft were built on the islets of Ponam and Pityilu, and around Seeadler Harbour fuel depots, ship-repair workshops, floating docks, hospitals and storehouses went up.

The base was also the subject of a dispute over jurisdiction. Admiral Chester Nimitz proposed that the development and control of the harbour be entrusted to the South Pacific forces under his authority, which MacArthur regarded as an encroachment on his command; for a time he restricted the use of the base to ships of the Seventh Fleet and British vessels. A compromise was negotiated in Brisbane by Admiral William Halsey; Kinkaid’s takeover of the base on 18 May put it into effect. In the end Seeadler Harbour was used by all the American fleets operating in the Pacific.

Place in the war

The capture of the Admiralty Islands, together with the unopposed occupation of Emirau on 20 March, closed the ring around Rabaul. The planned landing at Kavieng on New Ireland was cancelled, and some hundred thousand Japanese soldiers and sailors on New Britain and New Ireland were cut off; until the end of the war they played no further part beyond tying down Australian and American troops. The Allies did not have to storm Rabaul – bypassed, bombed and starved of supplies, it ceased to be a threat.

A secure rear base in the Admiralties allowed MacArthur to bypass the strong Japanese positions at Hansa Bay and Wewak and strike far to the west. As early as 22 April, before the formal end of the fighting in the islands, his troops carried out the landing at Hollandia (today Jayapura) and Aitape. At the end of May aircraft from the Admiralties supported the landing on Biak, and Seeadler Harbour became the rear base for the further advance along the coast of New Guinea. In the autumn of 1944 part of the invasion force for Leyte – the first step in MacArthur’s return to the Philippines – assembled here, and in 1945 the harbour also served the British Pacific Fleet. On 10 November 1944 the ammunition ship USS Mount Hood blew up there; her entire crew on board was killed, and 22 smaller vessels nearby were sunk or badly damaged.

The Admiralty Islands campaign, begun as a gamble, thus ended with a prize of strategic importance: the main forward fleet base in the South West Pacific, from which the Allies could reach out both towards the Philippines and towards the islands of the Central Pacific.