The naval base at Majuro Atoll was established to support two Marine dive-bomber squadrons, half a patrol squadron, and temporary staging for one Army fighter group. In addition, it was to provide Naval Air Transport Service requirements, fleet anchorage without shore-based facilities, medical facilities, and a loran transmitting station. Repair ships, submarine and destroyer tenders, together with tankers and supply ships, were to provide for the needs of the fleet.

     Majuro Atoll, in the Marshall group, consists of 56 islands, of which Majuro Island, at its western tip, is largest. The airstrip occupied the major portion of Dalop Island, on the eastern tip, and Uliga and Darrit Islands contained the base facilities, camps, and Port Director’s area.

     The surfaces of these islands are covered with coral sand which, in some places had acquired as topsoil through the decay of vegetation. Rainfall is heavy, and the climate tropical.

     Within the lagoon, depths run from 25 to 35 fathoms, with variable sand and coral bottom, relatively few coral heads existing other than in the western portion. The channel approach contains ample depth for the largest ships, and sand beaches afford excellent small boat and LST beaching areas.

     Army assault forces landed on January 31, 1944, and found the atoll unoccupied. The 100th Construction Battalion followed on February 1, together with the first echelon of a Marine defense battalion.

     Darrit Island had once been occupied by the Japanese, who left a 400ft timber pier, a narrow-gauge track from the pier leading to four frame warehouses, a seaplane ramp, and two steel buildings. At one end of a cleared area a large concrete slab had been poured for a hangar and structural steel was stacked nearby, from which  a warehouse was constructed. A frame building, located between the pier and the seaplane ramp, became the harbor captain’s office. Several food-storage buildings in the vicinity were also utilized.  Large frame native worker’s barracks became the maintenance ship building. Other barracks were made in to quarters for transients and a hospital; a seaplane hangar was converted into a warehouse; and smaller Japanese construction was used for various purposes.

     On Dalop Island a coral-surfaced airstrip, 5,800 by 445 feet, was constructed. This was used on D-Day-plus-12 for an emergency landing, and by April 15, the airfield, taxiways, aprons, housing, shops, and piers, s originally planned, were completed. Additional construction included 10 miles of coral roadways and 11,000 feet of 30-foot coral causeways connecting various islands.

     Acorn 8 dispensary, located among former Japanese quarters, was increased by the erection of Quonset huts and tents, its final capacity being 150 beds. Fuel-storage facilities were confined to gasoline-storage tanks; aviation gasoline storage was twelve 1,000-barrel bolted tanks set up on Bigariat Island, connected by 4-inch pipes to the underground ready-gas tanks at the airstrip. Delivery to the tank farm was by tanker, through a sea-loading line.

     Water was supplied by distillation, the 21 stills used for this work producing about 50,000 gallons per day. Storage tanks for fresh water included 25 wooden tanks of 160,000-gallon capacity, four 12,000-gallon canvas tanks, and two 8,000-gallon cisterns. The water was distributed to various points by pipe line and tank trucks. A deep-water floating pier, 625 by 28 feet, was constructed, and unloading operations were further facilitated by nine 4-by-12-pontoon and four 3-by-7-pontoon barges.

     Storage facilities erected, in addition to Japanese structures, were tents, tarpaulin-covered shelters, and 47 Quonsets. Ammunition was stored in several underground magazines, in three Quonset huts, and in open-storage revetments.
Shop facilities were located in 17 Quonset huts and 6,000 square feet of tarpaulin-covered shelters. The administration buildings included ten Quonset huts and 81 tents, as well as the Japanese buildings remodeled for the purpose. On Calanin Island, at the entrance to the approach channel, a signal station and a harbor entrance control post were established.

     Bomb-proof shelters were constructed at strategic locations, requiring a total of 350,000 cubic yards of coral fill. Fleet recreation facilities were also provided, all work being done by the 100th Battalion, supplemented in some cases by station personnel. The Seabee unit was housed in two tent cams, two companies living in the area adjoining the airstrip and the balance being based on Uliga, the main housing and administration.

     This construction was the work originally planned. The assignment of additional units to the base and the increased scope of activity necessitated considerable expansion.

     Fourth Marine Air Wing headquarters and Marine Air Group 13 established at Majuro Atoll in the middle of March 1944. These units required the construction of two 750-man camps, shop and storage facilities. At the airstrip, it was necessary to build seven Quonset huts, a nose hangar, and several lean-to structures, and to increase hardstands and apron facilities. A utility air squadron was also assigned to Majuro and required the standard number and types of headquarters buildings, ships, nose hangars, and parking facilities.

    When it was decided to locate the carrier replacement plane pool at Majuro, a strip, 175 by 4,000 feet, was cleared and paved on Uliga Island and a two-lane causeway connecting Uliga and Dalop was constructed, furnishing a 30-foot roadway. To accommodate air transport operations, a 150-by-800-foot apron was cleared and paved adjacent to the runway, with four Quonset huts to house office and storage facilities. Introduction of the plane pool activities demanded the doubling of carrier-aircraft service-unit personnel, and consequent enlargement of their living and shop facilities. The fleet recreation grounds and facilities were increased, and a submarine base recuperation camp was constructed which involved all installations necessary for a 750-man camp.

     All facilities were used to capacity as numerous bomber and fighter squadrons operated from the airfield. The carrier-aircraft service unit serviced the fleet carriers, and the plane pool serviced and furnished replacement planes. The harbor was used as a fleet anchorage and fleet recreation center. The sorting of supplies, mail storage, communications, and personnel replacement taxed the remaining station facilities to the utmost.

     Stevedoring duties were taken over from the 100th Battalion in February 1944, when Construction Battalion Detachment 1034 arrived in Majuro. This detachment of six officers and 250 men handled all cargo operations until August 1944, when they moved to Japtan Island in the Eniwetok  Atoll.

     The 60th Battalion performed all construction and maintenance work until relieved by CBMU 591 on June 18, 1944. The 60th left Majuro on July 5, 1944, for Pearl Harbor, CBMU 591 remained to take care of construction and maintenance. On V-J Day, all facilities were still operating at capacity, and no roll-up steps had been taken.