This was the US occupation of Emirau island in the St Matthias islands group of the Admiralty archipelago to the north-west of Kavieng on New Ireland island (20 March 1944).
Emirau is located about 90 miles (145 km) to the north-west of Kavieng, and is irregularly shaped with a length of 8 miles (12.9 km) and width of between 2 and 4.5 miles (3.2 and 7.25 km). Most of the island is a plateau ending in cliffs 75 to 185 ft (23 to 56 m) to the coastal plain, which is a few hundred yards wide and comprises mangrove swamps along much of the southern coast. Most of the coast is fringed with reefs, but there are reasonably good anchorages at Hamburg Bay in the north and Eulolou in the south. in the World War II period, the island was covered with a mix of light vegetation and jungle.
The island was completely undeveloped before World War II, with a single track along its length, together with a spur into the northern peninsula and a maze of trails in its western portion, and the Japanese presence was limited to a few coast watchers, but even these had been withdrawn by January 1944.
To complete the closure of the ring around the main Japanese base areas of Rabaul and Kavieng on New Britain and New Ireland islands, already partially enclosed by a series of operations including 'Cherryblossom' on Bougainville island, 'Squarepeg' on Green island, 'Postern' against Salamaua, Lae and Finschhafen on the Huon peninsula of North-East New Guinea, 'Michaelmas' on North-East New Guinea, 'Backhander', 'Director' (i) and 'Appease' on the western end of the island of New Britain, and 'Brewer' on the Admiralty islands, the Allies decided in February 1944 that Emirau island should be taken as the means of sealing the approaches to Kavieng in the north-west and north from the direction of the Caroline islands group, and thereby bringing 'Cartwheel' to an end.
On 12 March 1944 the Joint Chiefs-of-Staff Committee took the advice of Admiral Chester W. Nimitz, commanding the Pacific Ocean Areas and the Pacific Fleet, and cancelled the planned assault on Kavieng. Nimitz believed that the air campaign of the Air Solomons command against Rabaul had made such a move unnecessary. However, the amphibious force for the invasion had already been assembled by Admiral William F. Halsey, commanding the 3rd Fleet, at Guadalcanal, and two days later Halsey ordered Rear Admiral Theodore S. Wilkinson, the commander of the South Pacific Amphibian Forces, to take Emirau island.
The military logic of the undertaking was that the Allied presence on Emirau island would, in the longer term, provide a base from which to patrol the Ysabel Channel and so keep watch on Kavieng and the approaches to it and also, in the shorter term at least, provide a flank guard for 'Brewer' that was still proceeding on the Admiralty islands.
The task was assigned to Major General Harry Schmidt’s 4th Marine Division using the newly reactivated 4th Marines, which combined the four existing marine raider battalions. The Emirau Landing Force was created by Major General Roy S. Geiger’s I Marine Amphibious Corps on Guadalcanal island and organised into Brigadier General Alfred H. Noble’s brigade-sized Task Group A. Commodore Lawrence F. Reifsnider’s Task Group 31.2 (Emirau Attack Group) sailed from Guadalcanal on 17 March with the fleet carrier Enterprise, light carrier Belleau Wood, escort carriers Coral Sea and Corregidor, and light cruisers Biloxi, Cleveland, Columbia, Montpelier, Oakland and Santa Fe.
Fire support was provided by Rear Admiral Robert M. Griffin’s group of older battleships (New Mexico, Mississippi, Tennessee and Idaho), together with supporting warships, and these generated a diversion by pouring more than 13,000 14- and 5-in (356- and 127-mm) shells into the Kavieng area and its airfields on 20 March.
Local air cover was provided from the escort carriers Manila Bay and Natoma Bay, and escort was offered by a force of 15 destroyers.
The landing force arrived off Emirau island’s south-eastern end at dawn on 20 March in 19 destroyers and landing craft, and started to land four battalion landing teams. The 1 and 2/4th Marines landed unopposed on two beaches on the island’s south-eastern end as well as on nearby Elomusad islet. The island was swept, found unoccupied by the Japanese and, after all 3,727 men had landed, was declared secure by the fall of night.
On 23 March the Japanese navy seaplane base on the islet of Eloaue, off the south shore of of Mussau island to the north-west, was shelled by a force of destroyers. The garrison fled for Kavieng in two large native canoes, one of which was detected and destroyed on the following day.
'Seabee' construction battalions arrived on Emirau island within days, and began work on the construction on two airfields and small naval base. Within one month 18,000 men and 44,000 tons of supplies had come ashore, and by a time early in May the first airstrip had been completed. Eventually the island had two 7,000-ft (2130-m) runways on its northern peninsula.The 4th Marines were relieved by the 147th Infantry on 11 April. A PT-boat base was established on the islet of Eanusau and operated patrols off New Ireland.
With Rabaul and Kavieng neutralised and left to 'wither on the vine', Emirau island declined in importance from December 1944, and the base was closed in March 1945.