Naval Base Ulithi
Naval Base Ulithi was a major United States Navy base at the Ulithi Atoll in the Caroline Islands in the western Pacific Ocean, to the north of New Guinea during World War II. The base was built to support the island-hopping Pacific War efforts of the Allied nations fighting the Empire of Japan. In terms of the number of ships at one base, Naval Base Ulithi was the largest naval base in the world in 1944 and 1945, with over 600 ships at times.
Background
The Caroline Islands are now the Federated States of Micronesia nation. Micronesia comprises the Kosrae State, Pohnpei State, Chuuk State and Yap State. After the Spanish–American War in 1898, the islands became a German colony and German naval base.At the start of World War I in 1914, British warships destroyed the German colonial plantation owner's radio station. On 7 October 1914, Japan invaded and took over Yap Island without a battle. Japan and Britain made a treaty giving Japan the Pacific islands north of the Equator, signed at the Treaty of Versailles in 1919.
In the 1930s, Japan built naval and airbases on many of the islands; Truk Lagoon was the largest and strongest of these bases. By the start of World War II, Japan's Truk base had five airfields, fleet anchorage, a few seaplane bases, torpedo boat bases, repair facilities, and later a radar station. Japan also built a large base at Ponape, now Pohnpei. In that conflict, the United States Army Air Forces repeatedly bombed the Truk base, but it was bypassed in the amphibious landing war. By February 1944, US bombers had destroyed most of Truk's military assets, and by sea, the US Navy had cut off Truk and its garrison of 5,000 Japanese troops. The US also bypassed Ponape in the Senyavin Islands and its 8,000 troops.
The US Army 81st Division landed unopposed on Ulithi on 23 September 1944; the survey ship found the lagoon was well-protected and usable for fleet anchorage, with depths ranging from 80 to 100 feet. Soon, US Navy Seabees started work building the large base at Ulithi, taking advantage of the islands' geography: the Ulithi coral reef is about 20 miles long and 10 miles wide, with over 30 small islands. The four largest islands are Sorlen, Falalop, Asor, and Mogmog, and bases were built on all four. Japan bombed the US base at Ulithi a few times, with only marginal damage.
Base construction
Naval Base Ulithi was in use from 1944 to 1945 for staging operations and attacks on Japanese bases to the north, as part of US Naval Base Carolines. The US Navy Seabee 18th Special Battalion arrived on 1 October, followed by the 88th Naval Construction Battalion on 11 November. The Seabees did major construction on five islands of the atoll, notably including building a large fleet recreation center on Mogmog Island for 20,000 troops, docking piers, small plane airstrips, seaplane base, pontoon piers, and camps. On Mogmog Island, the Seabees built the Seabees' own base camp and Seabee supply depot. On Sorlen Island, they constructed a 1,600-place theatre, a large landing craft camp, 1,600-man mess hall, Naval headquarters, Marine aviation camp and 100-bed Naval hospital. Over 9,000 men were stationed at the base to run the operations.The Seabee 58th Naval Construction Battalion did R&R at Ulithi before departing to Okinawa Island. After Typhoon Cobra in December 1944, Naval Base Ulithi sent out ships to pick up survivors of ships that had sunk in the storm. Some ships that were damaged in the storm were also repaired at Ulithi.
Ulithi had a large fleet anchorage used for staging and repair of ships. The Seabees built an airbase to support half of a night fighter squadron, a utility squadron, and a light inshore patrol squadron. At the airbase, the Navy kept up to 150 aircraft fighter planes to replace any lost on aircraft carriers. Staging facilities for transport aircraft were constructed. A large camp was built for the maintenance crews of planes and ships. A camp was built to house crews of ships under repair. A supply depot was built to support the ships, planes, and troops at Ulithi. Most supplies like fuel, ammunition, and spare parts were stored in cargo ships in the atoll and unloaded as needed. Seabees handled over 20,000 tons of cargo per month.
The 18th Special departed 25 May 1945 to Leyte-Samar Naval Base. On 10 October 1944, part of the 6th Special Battalion arrived at Ulithi for unloading and loading of ships, with the 6th handling over 12,000 tons of cargo per month. The 6th departed in June 1945, ending its work. The 51st Battalion arrived on 8 October 1944 and widened, lengthened, and improved Falalop Airfield. A 3,500-by-150-foot fighter runway was built. The 51st also built a fuel tank frame and fuel pier. On 16 April 1945, the Seabee Naval Construction Battalion Detachment 1044 arrived. Most of the 1044th worked on damage control and repair sections at the base. The 1044 departed 25 July 1945, ending their work.
The 88th Naval Construction Battalion departed Ulithi on 7 February 1945 and arrived at Bobon, Samar, Philippine Islands on 10 February. There, they built a PT boat repair base as part of the Leyte-Samar Naval Base. On 8 November 1944, Naval Construction Maintenance Unit 603 arrived to do general maintenance of the airstrip. The Fleet Post Office at Ulithi was #3011. When Leyte-Samar Naval Base was completed, much of the operation at Ulithi was transferred to it, departing on 7 May 1945. During its operation, the base also supported the nearby Naval Base Kossol Roads.
Fleet support
The United States Fifth Fleet used Ulithi for staging major operations, including the Philippines campaign, Operation Hailstone and the troop landings at Okinawa. In March 1945 106 destroyers, 29 aircraft carriers, 15 battleships, and 23 cruisers departed for Okinawa. The base was kept secret until found by Japan, and Japan attacked the Fifth Fleet at Ulithi in Operation Tan No. 2 on 11 March 1945 using long-range kamikaze.In October 1944 a carrier battle group from Task Force 38 of the United States Third Fleet under William Halsey arrived at Ulithi for resupply. Murderers' Row was the nickname given to the Third Fleet's aircraft carriers at anchor in a row at Ulithi. In the row were,,,, and.
After the Third Fleet was hit by Typhoon Cobra in December 1944, it ported in Ulithi. The typhoon, which became known as Halsey's Typhoon, caused heavy damage to the ships, the sinking of three destroyers, and the loss of 146 aircraft. The destroyers lost were the,, and ; in total, 790 crewmen died. As a result, court of inquiry was held aboard the destroyer tender on 26 December to determine if Halsey should be sanctioned for sailing into the typhoon. The court found "errors in judgment committed under stress of war operations and stemming from a commendable desire to meet military requirements".
Attacks on the base
Japanese navy forces made several attacks on Ulithi, which represented an important strategic target, with over 100,000 barrels of fuel oil stored at Ulithi in tanker ships and land depots. Naval Base Ulithi also supported a number of other smaller bases in the Naval Base Carolines.On 20 November 1944, the fleet oiler was hit at Ulithi by a Japanese kaiten-manned torpedo; the ship exploded and sank, with a loss of 63 crew members. However, four other kaiten did not hit any other ships.
On 11 March 1945, the Operation Tan No. 2 kamikaze raid took off from Kanoya Air Field to attack Ulithi. The kamikaze aircraft hit in a nighttime raid on Ulithi, striking on her stern starboard side; Randolph lost 27 men and 105 were wounded. However, Randolph was quickly repaired at Ulithi and put back in service.
Japan planned a major submarine attack on Ulithi, but it was canceled with the surrender of Japan in September 1945, while the submarines were en route. With the news of surrender, the I-400 fleet returned to Japan.
Facilities
Airfields
- Falalop Airfield, now Ulithi Airport, on Falalop Island, built by Japan, but abandoned, improved by Navy Seabees. A single runway spanning the entire width of the island. US Marine Air Group 45, VMSB-24, and Service Squadron 45 with its headquarters were stationed at Falalop. MAG-45 and VMSB-24 flew missions to Japan's bases on Yap Island, Fais Island and Sorol Island, with their Grumman TBF Avenger, Grumman F6F Hellcat and Curtiss SB2C Helldiver. MAG-45 also flew anti-submarine patrols to protect Ulithi. The Marine Avengers sank two of the midget subs, only one sank a ship, a US Navy oiler at Ulithi.
- Sorlen Airfield on Sorlen Island, Built by Seabees, an airfield for light aircraft. Started 12 December 1944, and completed January 27, 1945.
- Mogmog Airfield, light aircraft, built on Mogmog Island to support the Mogmog Island Seabee camp and the Mogmog Island recreation center. Seabess started building on 12 December 1944 and completed on 27 January 1945.
- *At the three airfields the Navy kept up to 150 aircraft fighters to replace any lost on aircraft carriers.
- Mogmog seaplane base, a floating seaplane base, supported by seaplane tenders.
- Falalop Seaplane base on Falalop Island and in the atoll. Falalop Island base built starting 4 November 1944 and completed 5 December 1944
- Fais Airfield is to the east of Ulithi by 87 km on Fais Island. Ulithi supported the 3,000 feet runway built there in 1945. The runway was mostly used as an emergency landing strip.
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