page_title: Ulithi
section_title: Second World War
hierarchical_section_title: Ulithi / History / Second World War
caption_attribution_description: USS Iowa (BB-61) in a floating drydock at Manus Island, Admirality Islands, 28 December 1944.
context_page_description: Ulithi is an atoll in the Caroline Islands of the western Pacific Ocean, about 191 km east of Yap. It consists of 40 islets totalling 4.5 km², surrounding a lagoon about 36 km long and up to 24 km wide—at 548 km² one of the largest in the world. It is administered by the state of Yap in the Federated States of Micronesia. Ulithi's population was 773 in 2000. There are four inhabited islands on Ulithi Atoll. They are Falalop, Asor, Mogmog, and Fedarai. Falalop is the most accessible with Ulithi Airport, a small resort hotel, store and one of three public high schools in Yap state. Mogmog is the seat of the high chief of Ulithi Atoll though each island has its own chief. Other important islands are Losiap, Sorlen, and Potangeras.
  The atoll is in the westernmost of the Caroline Islands, 580 km southwest of Guam, 1,370 km east of the Philippines and 2,100 km south of Tokyo. It is a typical volcanic atoll, with a coral reef, white sand beaches and palm trees. Ulithi's forty small islands barely rise above the sea, with the largest being only 1.3 square kilometres in area.
context_section_description: Early in the Second World War, the Japanese had established a radio and weather station on Ulithi and had occasionally used the lagoon as an anchorage, but had abandoned it by 1944. As the operations of the United States Navy moved west across the Pacific, the Navy required a more forward base for its operations.
  Ulithi was perfectly positioned to act as a staging area for the US Navy's western Pacific operations.   The anchorage was large and well situated, but there were no port facilities to repair ships or re-supply the fleet.
  On 23 September 1944, a regiment of the United States Army's 81st Division landed unopposed, followed a few days later by a battalion of Seabees. The survey ship USS Sumner examined the lagoon and reported it capable of holding 700 vessels—a capacity greater than either Majuro or Pearl Harbor.
  The US Navy transferred the local islanders to the island of Fedarai for the duration of the hostilities. Arriving next was Service Squadron 10, termed by Admiral Nimitz as his "secret weapon". Its commanding officer, Commodore Worrall R. Carter, devised the mobile service force that made it possible for the Navy to convert Ulithi to the secret distant Pacific base used during the major naval operations undertaken late in the war, including Leyte Gulf and the invasion of Okinawa. Service Squadron 10 converted the lagoon into a serviceable naval station, creating repair facilities and re-supply facilities thousands of miles away from an actual naval port.  Pontoon piers of a new design were built at Ulithi, each consisting of the 4-by-12-pontoon sections, filled with sand and gravel, and then sunk.  The pontoons were anchored in place by guy ropes to deadmen on shore, and by iron rods driven into the coral. Connecting tie pieces ran across the tops of the pontoons to hold them together into a pier. Despite extremely heavy weather on several occasions these pontoon piers stood up remarkably well.  They gave extensive service, with little requirement for repairs. Piers of this type were also installed by the 51st Battalion to be used as aviation-gasoline mooring piers near the main airfield on Falalop.
  Within a month of the occupation of Ulithi, a complete floating base was in operation. Six thousand ship fitters, artificers, welders, carpenters and electricians arrived aboard repair ships, destroyer tenders, and floating dry docks. USS Ajax had an air-conditioned optical shop and a metal fabrication shop with a supply of base metals from which she could make any alloy to form any part needed. USS Abatan, which looked like a big tanker, distilled fresh water and baked bread and pies. The ice cream barge made 1,900 L (500 US gal) a shift.  The dry docks towed to Ulithi were large enough to lift dry a 45,000-ton battleship.  The small island of Mog Mog became a rest and recreation site for sailors.
  Fleet oilers sortied from Ulithi to meet the task forces at sea, refueling the warships a short distance from their combat operational areas. The result was something never seen before: a vast floating service station enabling the entire Pacific fleet to operate indefinitely at unprecedented distances from its mainland bases. Ulithi was as far away from the US Naval base at San Francisco as San Francisco was from London, England. The Japanese had considered that the vastness of the Pacific Ocean would make it very difficult for the US to sustain operations in the western Pacific.  With the Ulithi naval base to refit, repair and resupply, many ships were able to deploy and operate in the western Pacific for a year or more without returning to the Naval base at Pearl Harbor.
  The Japanese had built an airstrip on Falalop. It was expanded and resurfaced, the runway running the full width of the island.  The east end of the strip was extended approximately six metres (20 feet) past the natural shoreline.  A number of small strips for light aircraft were built on several of the smaller islands. The Seabees completed a fleet recreation center at Mog Mog island that could accommodate 8,000 men and 1,000 officers daily. A 1,
caption: USS Iowa at a floating drydock at Ulithi
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