This was the US seizure of Majuro atoll in the Marshall islands group of the central Pacific Ocean (31 January 1944).
Majuro lies in the southern part of the eastern Radak group of islands in the Marshall islands group, about 280 miles (450 km) to the south-east of Kwajalein atoll, 65 miles (105 km) to the north-west of Mille, 98 miles (158 km) to the south of Maloelap, and 117 miles (188 km) to the north-east of Jaluit. This atoll is 26 miles (42 km) long on its east/west axis and 6 miles (9.6 km) wide, with a land area of 3.7 sq miles (9.7 km˛) enclosing a lagoon with an area of 114 sq miles (295 km˛). Most of the atoll’s circumference is edged with a continuous reef, in which the only openings are on the north central side. The lagoon is entered though the Calalin Pass, which is 2 miles (3.2 km) wide. The lagoon is between 150 and 210 ft (45 and 65 m) deep and is an excellent protected anchorage, though there are a number of potentially dangerous coral heads in the western portion. The islets are covered with soil and salt brush, and the atoll experiences heavy rainfall.
The atoll comprises 64 islands and islets, of which Majuro island is the largest. It is a thin ribbon, nowhere more than 300 yards (275 m) wide, some 21 miles (33.75 km) long extending from the atoll’s south-western corner, where there is an a oval land mass measuring 1 mile by 1.75 miles (1.6 by 2.8 km), to the south-east as far as the point at which the reef makes a turn to the north-east. Sandbar islets are scattered along that side of the reef for about 12 miles (19.25 km). On the atoll’s narrow eastern end are three larger islets in the form, from south to north, of Dalap, Uliga and Darrit. More small islets dot the reef along its northern side to Calalin Pass, which is flanked on its eastern and western sides by Calalin island and Eroj islet. The submarine reef continues to the north-west, with a number of gaps, to a few islets on the atoll’s north-western corner. At its western side the reef had no islets.
By the outbreak of the Pacific War, the Japanese had built a small seaplane base on Darrit island on the atoll’s north-eastern corner. This installation included a 400-ft (120-m) timber pier, a narrow-gauge railway from the pier to a group of warehouses, and various support facilities.
Majuro was added to the list of objectives for 'Flintlock' on 26 December 1943 at the insistence of Vice Admiral Raymond A. Spruance, commander of the US 5th Fleet: Spruance had become concerned that the areas currently planned for refuelling at sea could be taken under attack by Japanese land-based aircraft, and saw in the atoll the type of secure refuelling area he envisaged. Given that the atoll was known to be only lightly defended, it was also to be secured and used as a base area on which to build airfields which would facilitate the maintenance of the lines of communications to Kwajalein atoll and protect that route from the Japanese-held islands which had been bypassed to the north and south. The atoll was also to be used as a temporary fleet anchorage as and when required.
The 'Sundance' Landing Force (the 2/106th Battalion Landing Team detached from Major General Ralph C. Smith’s 27th Division, and the V Amphibious Corps Reconnaissance Company) was allocated the task of taking Majuro atoll. Under the overall command of Rear Admiral Harry W. Hill, the commander of the 2nd Amphibian Group of the 5th Amphibious Force, the landing force was delivered by Task Group 51.2, the Majuro Attack Group, comprising the heavy cruiser Portland, escort carriers Nassau and Natoma Bay, destroyers Bullard, Black, Kidd and Chauncey, two minesweepers, one attack transport, two high-speed destroyer transports and one tank landing ship.
At about 23.00 on 30 January, one platoon of the reconnaissance company landed by rubber boat on Calalin island as the first US to land on an island possessed by Japan since before the war. The rest of the company landed on other islands and found that the Japanese had abandoned the atoll, even the seaplane base on Darrit island, a year earlier. Only Warrant Officer Nagata of the Imperial Japanese navy, who was taken by surprise and captured, and three civilians, who fled, were discovered on Majuro island.
The 'Sundance' Landing Force occupied Darrit and Dalap islands and the 1st Marine Defense Battalion soon arrived as the atoll’s garrison. Making use of the large quantity of equipment which the Japanese had left on the atoll, the US Navy quickly developed the previous Japanese seaplane base on Darrit island for its own use, and on Dalap island an airfield with a 5,800-ft (1770-m) runway was built, becoming usable as an emergency landing strip on 12 February, less than two weeks after the landing. By this time the US strength on Majuro atoll had risen to 5,000 men. Considerable use was made of existing Japanese facilities and supplies.
Minimal fleet support facilities were constructed, and the air facilities were expanded as the Fleet Anchorage, Naval Base, and Naval Air Facility, Majuro. A 4,000-ft (1220-m) fighter airstrip was built on Uliga island and a coral causeway was built to connect Dalap and Uliga islands as well as others to provide a road 35 miles (56 km) long. The 4th Marine Base Defense Aircraft Wing Headquarters was based at Majuro atoll.
US submarines soon began to evacuate the native populations of Japanese-controlled islands, whose bombardment was continued, both to protect them and to deny the Japanese their labour, and 4,000 of them were accommodated on Majuro atoll. The US Navy provided for the needs of the evacuated civilians and after the end of the war returned them to their home islands.
The Majuro atoll base remained fully operational for the rest of the Pacific War, and was closed on 23 June 1947.