Caroline Islands
by Jack McKillop

Physical Description & History

     The Caroline Islands are in the western Pacific Ocean east of the Philippine Islands extending from 5° to 10°N and 130° to 166°E. They comprise the most extensive island chain in the world. Depending on the definition of islands, there are between 550 and 680 islands and many coral islets and reefs covering 457 square-miles (1,184 square-kilometers) without lagoons and 3,740 square-miles (9,687 square-kilometers) including lagoons. An idea of the smallness of the individual islands (mostly coral atolls) is conveyed by comparative statistics: although eight times more numerous than the Mariana Islands, the Carolines contain only slightly more than two-thirds the land area of that neighboring group, members of which, in turn, are unimpressive as compared to islands in Melanesia and Polynesia.
     The islands were discovered by a Spanish explorer in 1526. Spain professed shadowy claims to possession of the Palaus, along with all the Caroline and Mariana Islands, but showed little interest in their development for more than a century. The Spanish government officially made an attempt to assert her rights to these islands in 1875 and they were placed under the Spanish East Indies with the administrative center in Manila, Philippine Islands. By 1885 her jurisdiction had become so tenuous that colony-hungry Germany had no hesitation in hoisting their flag on Yap Island and laying claim to the entire area in the name of the new German Empire. Germany disputed the Spanish claim, and the matter went to the arbitration of Pope Leo XIII in 1885. He decided in favor of Spain, but gave Germany free trading rights. The Spanish did not occupy any island formally until 1886.
     The Treaty of Paris was signed in 1898 as a result of the Spanish-American War and Spain surrendered the island of Guam and the Philippine Islands to the United States for a payment of US$20 million (over US$450 million in 2011 dollars). This left Spain with about 6,000 tiny, sparsely populated islands in the Pacific. With the loss of two fleets in the war and Guam and the Philippines, Spain decided to sell all her remaining possessions to Germany in 1899. The sale included the Caroline, Mariana and Palau Islands.
     When World War I began in 1914, the Japanese formally declared war on the German Empire on 23 August 1914 and began occupying the islands. In 1920, the Japanese were given a League of Nations mandate over the Caroline Islands.
     The USN built two bases in these islands during World War II, one on Peleliu in the Palau Islands of the western Carolines and the second on Ulithi Atoll in the eastern Carolines.

Peliliu, U.S. Naval Base

    The Palau Islands are a group of about 100 islands and islets extending from 6°53' to 8°12'N and 134°08' to 134°37'E. They are located about 1,040-miles (1,674-kilometers) east-southeast of Manila, Philippine Islands and 280-miles (451-kilometers) west-southwest of Japanese-held Yap Island. The total land area is 177 square-miles (459 square-kilometers). The chief island is Babelthuap and other islands are Angaur, Eli Malk, Koror, Peleliu and Urukthapel.
     Naval Base (NB) Peleliu was built on Peleliu Island (7°01'N, 134°15'E) at the southern end of the Palau Islands. Peleliu is 5.5-miles (8.9-kilometers) long and 2.5-miles (4.0-kilometers) wide; total land area is 5 square-miles (13 square-kilometers). The major portion of the land is low and level, but the central and northern portions contain numerous high rock ridges. Swamp areas, extending north and south, divide the island except for a minor strip on which its single east-west road is built. The coastline is mostly rocky but has about 2-miles (3.2-kilometers) of scattered sandy beaches.
     Although the Palau group offers a spacious and well-protected anchorage for major fleet elements, no major Japanese facilities existed for construction or repair of any but small craft. The Japanese had three airfields in the Palau group, the largest of which was located on Peleliu. A new operational strip was on the small island of Ngesebus, just north of Peleliu and connected to it by a bridge in the last stages of construction. A third field was still under construction at Airai, near the southern end of Babelthuap Island.
     Peleliu Airfield (6°59' 53"N, 134°13' 59"E), a cleared area at the southern portion of the island, contained two runways in an X pattern, one 3,900-feet (1,189-meters) long and the other 3,850-feet (1,173-meters) long. There were two sizable service aprons, connected with each other, and with turning circles, by hard-surfaced taxiways. Good roads lined the northern coastal areas with the airfield.
     On 15 September 1944, elements of the U.S. 1st Marine Division landed on the island and captured the airfield by the next night. On the 17th, Marine Stinson OY-1 Sentinels were based on the airstrip providing artillery spotting capability. The Seabees began work to extend the airfield to 6,000-feet (1,829-meters) to accommodate U.S. Army Air Forces B-24 Liberators on 23 September. On 24 September, the first Marine night fighter squadron arrived with F6F Hellcats followed two days later by a Marine fighter squadron with F4U Corsairs. Marine aviation units remained on the island until the end of the war flying antisubmarine missions and attacks on Japanese-held islands in the Palau Islands and Yap Island.
     The island was declared secured at 1100 hours local on 27 November.
     Airfield development continued during the early months of 1945 and when completed, the bomber strip measured 6,000- by 300-feet (1,829- by 91-meters), and the fighter runway, 4,000- by 250-feet (1,219- by 76-meters). Taxiways and parking areas were constructed to support the assigned seven squadrons and 100 transient and cargo planes that would be based here.
     The Seabees also erected four Quonset-type warehouses for aviation shops, 20 Quonset huts for offices and repair facilities, and complete camp installations for aviation personnel. By January 1945, construction was completed on a tank farm, consisting of one 10,000-barrel tank for vehicle gasoline, twenty 1,000-barrel tanks for aviation gasoline, and three 1,000-barrel tanks for diesel oil.
     Two hospitals were also constructed, one for the Army and one for the Navy. The Army hospital had a 440-bed capacity and was completed in November 1944. Work then began on the naval hospital, and by the end of December, six H-type Quonset-hut units, of 100 beds each, had been completed with all facilities. Due to delay in the arrival of materials, the 320-bed annex to the Navy hospital was not completed until March 1945. Numerous dispensaries, with a total capacity of 161 beds, were also provided for various naval activities.
     By the end of January 1945, minor waterfront facilities were complete. A Japanese concrete-block pier was rebuilt and provided berths for three light craft. The approach channel was dredged to a 10-foot (3.0-meter) low-water depth and a landing craft, tank (LCT) landing beach prepared.
     Three major supply centers had been established by early 1945. Eight Quonset-type warehouses, with concrete floors, were built for this activity. Five Quonset buildings were built for the aviation supply depot and four 20- by 50-foot (6.1- by 15-meter) magazines were erected.  The spare parts depot consisted of four Quonset buildings, with concrete floors and unloading platforms, and several Quonset huts for offices. More than 16-miles (26-kilometers) of primary roads were built to serve these activities on Peleliu.
     As the war moved west, the importance of NB Peleliu decreased; the base was finally disestablished in 1947. The islands then passed formally to the United States under United Nations auspices on 18 July 1947 as part of the Trust Territory of the Pacific Islands. The territory was comprised of the Mariana, Marshall and Palau Islands. The Republic of Palau was established in 1981 and concluded a Compact of Free Association with the U.S. which was effective on 1 October 1994. The Republic of Palau is now a member of the United Nations.

Ulithi Atoll, U.S. Advanced Fleet Anchorage

     Ulithi Atoll (9°57'N, 139°39'E) is in the eastern Caroline Islands and located about 110-miles (177-kilometers) east-northeast of Japanese-held Yap Island and 420-miles (676-kilometers) southwest of Guam Island in the Mariana Islands. It is a typical volcanic atoll consisting of 40 islets that barely rise above sea level. Total land area is 1.7 square-miles (4.5 square-kilometers), surrounding a lagoon about 22-miles (36-kilometers) long and up to 15-miles (24-kilometers) wide—at 212 square-miles (548 square-kilometers), one of the largest lagoons in the world. The average depth of the lagoon is from 80- to 100-feet (24- to 30-meters). The chief islands in the atoll are Falalop and Agor on the east and Mogmog on the north.
     During World War II, the Japanese had built an airfield and a seaplane base on Falaop Island (10°01' 00"N, 139°47' 26"E). They had also built a radio and weather station on one of the islands and the lagoon was used occasionally as a fleet anchorage early in the war but by 1944, the Japanese had evacuated the islands.
     The U.S. wanted a forward operating base and Ulithi Atoll was ideal. On 23 September 1944, a regimental combat team of the U.S. Army’s 81st Infantry Division landed unopposed and secured the atoll. The Army found about 400 native residents and three Japanese soldiers. The natives on the four largest islands were moved to smaller Facer Island, and every inch of these four islands was quickly put to use. Agor Island (10°01' 43"N, 139°46' 00"E) had room for a headquarters, port director, radio station, evaporator (rain is the only freshwater supply), tents, small boat pier and cemetery. Sirloin Island (10°04' 48"N, 139°44' 11"E) was set up as a shop for maintaining and repairing the 105 landing craft, vehicle and personnel (LCVPs) and 45 landing craft, mechanized (LCMs) that became beasts of all work in the absence of small boats. Mogmog Island (10°05' 18"N, 139°42' 29"E) was assigned to recreation. The big island, Falaop, was just wide enough for an airstrip to handle the Douglas R4D Skytrains and Curtiss R5C Commandos, which would presently fly in 1,269 passengers, 4,565 sacks of mail and 262,251 pounds of air freight a week from Guam.
     A Navy Seabee battalion arrived on 8 October 1944 and was tasked to widen, lengthen and improve the Japanese airfield on Falaop Island. A 3,500- by 150-foot (1,067- by 46-meter) runway was completed in 27 days. The east end of the runway extended approximately 20-feet (6.1-meters) past the natural shoreline of the island, log cribs being used as foundation for this addition to the island. The first plane landed on the strip 15 days after work was begun. Six taxiways were constructed; one, 4,000- by 100-feet (1,209- by 30-meters); one, 3,250- by 700-feet (991- by 213-meters); and four, 500- by 100-feet (152- by 30-meters). Also installed were hardstands, lighting, a traffic-control tower, operations buildings, aviation-gasoline ready tanks, and a tank farm. All work was completed by December. The air base was designed to support half of a night fighter squadron, a light inshore patrol squadron, a pool for a maximum of 150 carrier replacement aircraft, a utility squadron, and staging facilities for transport aircraft.
     A seaplane ramp was also constructed at one end of the main airfield. This ramp, which extended from extreme low-water mark to the hardstand, was 50- by 95-feet (15- by 29-meters), surfaced with pierced plank, and protected along the outer edges by a concrete slab. Work was begun on 4 November, and completed on 5 December, five days ahead of schedule.
     One of the major construction jobs on Ulithi was that of a fleet recreation area on Mogmog Island. The selected area was cleared, and a swamp area filled with coral, to eliminate mosquitoes and insects. Construction of the recreational facilities began on 15 October. Numerous facilities for sports, a bandstand, and beverage storage were provided. When completed in January 1945, the center could accommodate 8,000 men and 1,000 officers daily. A 1,200-seat theater, including a 25- by 40-foot (7.6- by 12.2-meter) stage with a Quonset hut roof, completed in 20 days was ready for use on 20 December 1944.
     Massive construction was also begun on Sirloin Island, in the northern part of the atoll located about 1.5-miles (2.4-kilometers) east of Mogmog Island. This included a 500-seat chapel, a  theater seating 1,600 men, facilities for a standard landing craft unit, grading the entire island and covering it with Quonset huts for storage, shops, mess halls, offices, living quarters, and building roads, supply dumps, and necessary facilities to supply water and electricity to all parts of the island. Eleven distillation units, drawing water from the sea, and nine 5,000 U.S. gallon (4,163 Imperial gallon or 18,927 liter) storage tanks were set up to provide drinking water. A hospital including Quonset huts and supplementary facilities to house and operate a 100 bed unit plus erection of 42 Quonset huts for use as a receiving station, and a 1,600 man mess hall, complete with galley, warehouses and refrigeration units were also built.
     Additional construction on the islands included three airstrips, one each on Falaop, Mogmog, and Sirloin Islands, for light plane operations between islands of the atoll, the atoll commander's headquarters, a dispensary, an administration building, a shop and Marine aviation camp. In addition to general maintenance of the airstrip and taxiways, the Seabees constructed a sewage disposal system for the Marine and Seabee galleys. Construction of a 3,000-man galley, a refrigeration storage building, a butcher shop, an issue room, a bakery, an officers' mess, and shops for a landing craft unit was another important task. Other construction included enlarging and improving a finger pier and the removal of 10,000 cubic yards (7,646 cubic-meters) of coral to improve beaching facilities for landing craft.
     Within a month of the occupation of Ulithi, a whole 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 repair ship USS Ajax (AR-6) 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 distilling ship USS Abatan (AW-4), which looked like a big tanker, distilled fresh water and baked bread and pies. The ice cream barge made 500 U.S. gallons (416 Imperial gallons or 1,893 liters) a shift. The dry docks towed to Ulithi could accommodate a battleship. Fleet oilers sortied from Ulithi to refuel the combat ships a short distance from the strike 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 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, Territory of Hawaii.
     On 16 November 1944, the oiler USS Mississinewa (AO-59) replenished her cargo tanks, filling them almost to capacity with 404,000 U.S. gallons (336,400 Imperial gallons or 1.53 megaliters) of aviation gasoline, 9,000 barrels of diesel oil, and 90,000 barrels of fuel oil. Four days later she was still anchored in the lagoon and at 0547 hours local, shortly after reveille, a heavy explosion rocked the oiler. Massive flames immediately burst from midship forward. Fanned by a light wind, the fire spread aft quickly. A few minutes after the first explosion, the fires reached the after magazine and another explosion, heavier than the first, tore through the ship. The ship was abandoned and soon enveloped in flames over 100-feet (30-meters) high. At about 0900 hours the ship slowly turned over and disappeared. Fifteen minutes later the fire on the water was out and Ulithi anchorage was again quiet. Postwar inquiry found that USS Mississinewa, with 60 of her crew, was the first victim of the kaiten, the Japanese manned torpedo (fired by Japanese submarine HIJMS I-36). The was the first kaiten mission of the war.
     During 1945, the Japanese initiated two other attacks on Ulithi. On 11 January, Japanese submarines commenced operation Kongo, employing kaiten suicide torpedoes. The following day, submarine HIJMS I 36 launched kaitens that damaged ammunition ship USS Mazama (AE-9). An explosion rocked the ship at 0654 hours local and she developed a 2 degree list to port and was down at the head. Pumps were immediately started to counteract flooding, later ballast was emptied to reduce the forward draft which had increased to 35- from 23-feet (11- from 7.0-meters) and the change in draft aft, from 25- to-21 feet (7.6- to 6.4-meters). By midafternoon, having suffered the loss of eight men, one dead and seven seriously injured, Mazama began to transfer serviceable ammunition; unservicable munitions were dumped at sea. A kaiten also damaged  infantry landing craft LCI-600
     The second attack occurred on 11 March 1945 when Frances medium bombers (Yokosuka P1Y, Navy Bombers Ginga), flying direct from Kanoya, Japan, attacked the fleet anchorage. One Frances hit the aircraft carrier USS Randolph (CV-15) on the starboard side aft just below the flight deck, killing 25 men and wounding 106. Another Frances crashed into Sirloin Island. Salvage vessel USS Current (ARS-22) was also damaged by collision with USS Randolph during fire-fighting operations.
     The surveying ship USS Sumner (AGS-5) had surveyed the lagoon between September 1944 and February 1945 and it was estimated that over 700 ships could be anchored there at a time. By 13 March 1945 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 in the Philippine Islands was secured, the Pacific Fleet moved its forward staging area to Leyte, and Ulithi was all but abandoned. In the end, few U.S. 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. A weather station continued to operate until 1948 but all other facilities were closed up by 27 December 1945.
     After the war, Ulithi became part of the Trust Territory of the Pacific which entered United Nations trusteeship on 18 July 1947 and was administered by the United States. The U.S. Navy controlled the territory from its headquarters on Guam until 1951, when the U.S. Department of the Interior took over control, administering the territory from its base on Saipan Island.
     On 10 May 1979, four of the Trust Territory districts ratified a new constitution to become the Federated States of Micronesia (FSM). Palau, the Marshall Islands, and the Northern Mariana Islands chose not to participate. The FSM signed a Compact of Free Association with the United States, which entered into force on 3 November 1986, marking Micronesia's emergence from trusteeship to independence. Ulithi is administered by the state of Yap in the FSM.