On 26 February 1944, the United States CNO FADM Ernest J. King authorized the construction of five vessels in response to a British Royal Navy request for several Heavy Duty Fleet Repair Ships. These ships were to have been constructed in the United States and later transferred to Britain under the Lend-Lease agreement.^[1] The hull alterations and armament were to be based on the ARG type, and BuShips was then to install such repair ship facilities as could be accommodated. Liberty hulls already under construction for allocation to the U.K. were selected for the conversions. In a preliminary planning meeting on 3 February 1944, an effort was made to use the plans of Tutuila (ARG-4), but it soon became apparent that the characteristics desired by the British differed in so many details that entirely new internal arrangement plans would be needed. Arguments over the alterations continued into June 1944, with the U.S. reportedly insisting on retaining some items that would make the ships suitable for U.S. use if they did not go to the U.K. Initially all five were to have been transferred to Britain under Lend-Lease, and the British assigned names to all five, but the last three were reallocated to the USN on 23 Nov 44 before completion. AR-19, the only unit not converted at Baltimore, was modified at East Boston, Mass. where she was towed in late August 1944; her commissioning was delayed by the late delivery of a diesel generator auxiliary power switchboard.

Xanthus-class vessels were first laid down in mid-1944 by Bethlehem-Fairfield Shipyard under a Maritime Commission contract. These ships were originally intended as Liberty ships, hull design EC2-S-C1 (which, at the time, were also under construction for Britain).^[2] Instead, five of the partially completed Liberty ship hulls were requisitioned for conversion into repair ships.

It was soon realized that the Liberty ship hull and configuration would not be suitable for the role of repair ship. Substantial modification was necessary in order to ensure operating efficiency and functionality. A planning commission investigating the problem decided that the modifications would be based on the design of Luzon-class repair ships, ARG type repair ships which had already seen substantial service in the Pacific. Construction proceeded, with initial hull alterations and armament based on the Luzon class. The Luzon-class repair ship USS Tutuila (ARG-4) was selected as the conversion template. It was quickly realized that conversion based ultimately off the Luzon would not be entirely successful, because British configuration requirements for the ships differed substantially from the Luzon design. A complete overhaul of the internal configuration, and thus completely new plans for the internal configuration, were necessary.^[3]

Each remained in Bethlehem-Fairfield Shipyard for most of the construction process. At approximately 80% completion, the ships were transferred to the conversion docks. Four of the five ships remained in Maryland and were converted by the Maryland Drydock Company. The other ship, AR-19, was sent to Bethlehem-Simpson Yard in Boston, Massachusetts.^[4]

While all five ships were intended for the Royal Navy, only two were delivered. The other three were expropriated by the US Navy sometime prior to completion and were given the Xanthus class designation.^[5]

Xanthus-class vessels provided a diverse range of auxiliary repair functions for both the US and British navies. American-flagged ships served in the Pacific with the US Navy, repairing ships damaged in the final battles against Japan. These ships continued their role after the war by providing support for the Allied occupation of Japan. British flagged ships served in the Atlantic with the Royal Navy repairing both aircraft and destroyers before being returned to the United States shortly following the war's end.

One ship, USS Laertes, also served in the Korean War.

HMS Assistance (F173) / (AR-17) edit

HMS Assistance was laid down in May 1944 and delivered to the Royal Navy on 20 January 1945. The ship served in British home waters as an aircraft depot and repair ship.^[6] She was returned to US Navy and transferred to the National Defense Reserve Fleet in 1946.

HMS Diligence (F174) / (AR-18) edit

HMS Diligence was laid down in June 1944 and transferred to Britain in 1945. She served as a destroyer repair vessel until returning to US Navy in 1946. She was subsequently transferred to National Defense Reserve Fleet.^[7]

USS Xanthus (AR-19) edit

USS Xanthus was laid down in June 1944, launched in July and finally commissioned in May 1945. She arrived at Pearl Harbor on 20 July 1945 and briefly served in the repair role. On 11 August, Xanthus sailed for Alaska, where she was to join forces massing for the planned assault on the Japanese held Kuril Islands. The invasion never took place, and instead Xanthus was sent to Japan, where she served as the flagship of Task Group 56.2. Xanthus later operated out of Okinawa until January 1946.

In February 1946, Xanthus sailed for China where she supported American naval activities. She was withdrawn in April of that year and sent to the National Defense Reserve Fleet in James River, Virginia.^[8]

USS Laertes (AR-20) edit

USS Laertes was laid down in August 1944, launched in September and commissioned in March 1945. She was sent to the naval facilities at Enewetak Atoll, where she spent four months repairing battle damaged ships. From there she sailed to Okinawa, where she spent only a week before setting course for the United States. Laertes served several months as a pre-inactivation repair ship in Bremerton, Washington and San Diego, California before being decommissioned and entering the Pacific Reserve Fleet.

Laertes was recommissioned on 19 December 1951 in response to the outbreak of hostilities in Korea. She operated from the Japanese port of Sasebo and the Korean port of Pusan repairing the battle damaged ships of the United States Seventh Fleet.^[9]

USS Dionysus (AR-21) edit

USS Dionysus was laid down in September 1944, launched in October and commissioned in April 1945. She operated from Enewetak Atoll and Tokyo Bay between July and September 1945.

She was recommissioned in 1952 and joined the Atlantic Fleet, where she repaired ships in Puerto Rico and in ports along the Eastern United States.^[10]

The class and the lead ship were named after Xanthus, one of Achilles' horses who spoke with a human voice.^[11]

• List of support ships of the Royal Navy
• List of auxiliaries of the United States Navy
• War in the Pacific

• Xanthus class on The Pacific War Online Encyclopedia
• Repair ships of the US Navy 1940–1945

This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.