Ulithi Ulithi is an atoll in the Caroline Islands of the western Pacific Ocean , about 191 km ( 103 nautical mi ) east of Yap . It consists of 40 islet s totalling , surrounding a lagoon about long and up to wide — at 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 an air strip , a small resort hotel , gas dealership , 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 . Ulithi was a major staging area for the U . S . Navy in the final year of the Second World War . Several sunken warships rest at the bottom of the Ulithi lagoon , including the USS " Mississinewa " , a fully loaded fleet oiler . The sunken tanker was found to be seeping oil into the lagoon . The United States Navy responded , locating the tanker , tapping her storage tanks , and pumped off her oil . The clean up operation was completed in February 2003 . The atoll offers good fishing and diving , though recent typhoons have eroded some of the reefs . Census records can be misleading because population can fluctuate during the year because it is common for Ulithians to leave for work or school abroad and to return . This is particularly true during festive times like the Outer Island High School graduation ceremony , when the population can increase considerably . Additionally , during events like weddings and funerals , Yasor ' s population may double . Electricity is now available on some islands , and the advent of video players and cell phones have brought a touch of the outside world to this very isolated atoll . Occasional diving and adventure tours visit Ulithi from Yap . Western clothing is prohibited on Mogmog island for everyone including tourists . History . The first European to find Ulithi was the Portuguese navigator Diego da Rocha , in 1526 . Its visit was recorded by Spanish navigator Álvaro de Saavedra on board of ship " Florida " on 1 January 1528 . He named them " Islas de los Reyes " ( Islands of the Three Wise Kings in Spanish ) because of the sighting happening on the eve of Epiphany . It was later charted by the Spaniards as " Islas de los Garbanzos " ( Chickpeas Islands in Spanish ) . It remained undisturbed by Europeans until visited and explored in detail by Captain Don Bernardo de Egoy in 1712 , and later visited by Spanish Jesuit missionaries led by Juan Antonio Cantova together with a group of 12 Spanish soldiers in 1731 . Germany purchased the islands from Spain in 1899 . They were occupied in 1914 by Japan at the outset of the First World War . Japan received them in 1920 as a League of Nations mandate . As the Second World War moved west across the Pacific , the US Navy required a more forward base for operations . The Japan ese had established a radio and weather station on Ulithi and had used the lagoon as an anchorage occasionally early in the war , but had abandoned it by 1944 . Ulithi was perfectly positioned to act as a staging area for the US Navy ' s western Pacific operations . The atoll is in the westernmost of the Caroline Islands , southwest of Guam , east of the Philippines and 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 half a square mile in area . However the reef runs roughly twenty miles north and south by ten miles across , enclosing a vast anchorage with an average depth of 80 to . The anchorage was well situated , but there were no port facilities to repair ships or re - supply the fleet . On September 23 , 1944 , a regiment of the US 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 . It became the undisclosed Pacific base for major operations late in the war , including Leyte Gulf and the invasion of Okinawa . The US Navy transferred the local islanders to the island of Fedarai for the duration of the hostilities . Next came what Admiral Nimitz called his " secret weapon " , Service Squadron 10 . Commanding officer Commodore Worrall R . Carter devised the miraculous mobile service force that made it possible for the Navy to create repair facilities and re - supply facilities thousands of miles away from an actual Naval port . Service Squadron 10 was called upon to convert the lagoon into a servicable naval station . 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 . The 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 . The USS " Abatan " , which looked like a big tanker , distilled fresh water and baked bread and pies . The ice cream barge made 500 gallons 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 twenty 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 , 200 - seat theatre , including a 25 - by - 40 - foot stage with a Quonset hut roof was completed in 20 days . At the same time , a 500 - seat chapel was built . A number of the larger islands were used both as bases to support naval vessels and facilities within the lagoon . The Japanese still held Yap . Early after the US occupation they mounted a number of attacks but caused no damage to the Seabees working on the islands . On 20 November 1944 the Ulithi harbor was attacked by Japanese kaiten manned torpedoes launched from two nearby submarines . The destroyer USS " Case " rammed one in the early morning hours . At 5 : 47 the fleet oiler USS " Mississinewa " , at anchor in the harbor , was struck and sunk . Destroyers began dropping depth charges throughout the anchorage . After the war Japanese naval officers said that two tender submarines each carrying four manned torpedoes had been sent to attack the fleet at Ulithi . Three of the suicide torpedoes were unable to launch due to mechanical problems and another ran aground on the reef . Two did make it into the lagoon , one of which sank the USS " Mississinewa " . A second kaiten attack in January 1945 was foiled when the " I - 48 " was sunk by the destroyer escort USS " Conklin " . None of the 122 men aboard the Japanese submarine survived . On March 11 , 1945 , in a mission known as Operation Tan No . 2 , several long range aircraft flying from southern Japan attempted a nighttime kamikaze attack on the naval base . One struck the Essex - class aircraft carrier USS " Randolph " , which had left a cargo light on despite the black out . The plane struck over the stern starboard quarter , damaging the flight deck and killing a number of crewmen . Another crashed on Sorlen Island , having perhaps mistaken a signal tower there for the superstructure of an aircraft carrier . By March 13 there were 647 ships at anchor at Ulithi , and with the arrival of amphibious forces staging for the invasion of Okinawa the number of ships at anchor peaked at 722 . After Leyte Gulf was secured , the Pacific Fleet moved its forward staging area to Leyte , and Ulithi was all but abandoned . In the end , few US civilians ever heard of Ulithi . By the time Naval security cleared release of the name , there were no longer reasons to print stories about it . The war had moved on , but for seven months in late 1944 and early 1945 , the large lagoon of the Ulithi atoll was the largest and most active anchorage in the world . Language . In an annual report released in early 2010 , the Habele charity announced plans to develop and distribute native - language materials for educators and students in the outer islands of Yap State , Micronesia . The first project was a Ulithian - to - English dictionary . This was the first rigorous documentation of the Ulithian language , and copies were provided to educators and students throughout Ulithi and Fais The authors ' stated aim was to create a consistent and intuitive Latin alphabet useful for both native Ulithian and native English speakers .