King authorized the construction of five vessels in response to a British Royal Navy request for several Heavy Duty Fleet Repair Ships.

[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.

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.

[5] Xanthus-class vessels provided a diverse range of auxiliary repair functions for both the US and British navies.

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.

On 11 August, Xanthus sailed for Alaska, where she was to join forces massing for the planned assault on the Japanese held Kuril Islands.

She was sent to the naval facilities at Enewetak Atoll, where she spent four months repairing battle damaged ships.

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.

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.