Ajax was laid down on 7 May 1941 at Los Angeles Shipbuilding and Dry Dock Company, San Pedro, California, launched on 22 August 1942.

On 13 June, she sailed for Eniwetok to help set up an advance repair base where she labored through August, at one time working extensive jobs on 19 cruisers and nine battleships.

Quarantine ended on 10 October, and Ajax steamed to Ulithi to resume repair work and to handle her first major battle damage job.

Severely damaged during a torpedo attack off Formosa, Canberra (CA-70) received sufficient temporary repairs alongside Ajax to enable the cruiser to continue on to Manus.

[1] On 25 May 1945, Ajax headed for Leyte-Samar Naval Base in San Pedro Bay, Leyte Gulf, to help prepare for the final assault on Japan, spending July repairing typhoon-battered USS Bennington (CV-20).

[1] Upon learning of Japan's capitulation on 15 August, Ajax began readying amphibious and transport ships to carry occupation forces to the Japanese home islands.

[1] The yard work ended on 23 February 1946, and Ajax sailed via Pearl Harbor for the Bikini Atoll to participate in the atomic bomb tests to be held there in July by conducting salvaging, towing, and emergency repairs.

[1] Ajax returned to San Diego on 26 April and devoted the next four and one-half months to operations in various shipyards and ports along the coast of California.

[4] Ajax returned from the United States to Japan in February 1960 and in June received orders changing her home port from San Diego to Sasebo.

A scheduled two-day visit to the last port became a three-week stay in March and April when Ajax remained there as backup repair ship in the event that President John F. Kennedy's strong diplomatic resistance to communist aggression in Laos would involve the American Navy in hostilities.

The repair ship's technicians worked around the clock for seven days to complete the job and return Boston to her ready status.

After her arrival in Sasebo on 23 July, Ajax provided routine repairs and service support for ships there and in Yokosuka for the remainder of the year and the beginning of 1969.

[1] Ajax continued her usual routine of servicing ships in Sasebo, Yokosuka, and Subic Bay during 1969, including a two-week stay in Vung Tau from 27 September to 10 October.

The ship spent September in Vung Tau, but her month of hard work there was followed by five days of rest and relaxation in Hong Kong before she returned to Sasebo on 1 October.

On 27 January 1972, ComServGru 3 shifted his flag to Hector; and Ajax steamed via Pearl Harbor to San Diego, where she arrived on 16 February and served for the remainder of the year.

[1] Ajax again got underway westward on 16 January 1973 and stopped at Pearl Harbor before arriving in Sasebo on 6 February to relieve USS Jason as flagship.

Typhoon Dot complicated the second cruise by closing Hong Kong harbor and causing Ajax to circle in rough waters for two extra days before pulling into port.

A series of labor strikes by Japanese employees gave the repair ship's crew members the opportunity to prove their expertise and capabilities.

Besides carrying out their normal duties, they helped run the base utilities and acted as firemen, bus drivers, and skilled practitioners of many other occupations to aid the naval activity.

During her busy three months in the Indian Ocean servicing 31 ships, Ajax made a brief visit to Port Louis, Mauritius, for recreation.

On 12 October, after being relieved by USS Emory S. Land, Ajax sailed eastward; stopped in Bunbury and Sydney, Australia; Pearl Harbor; and finally reached San Diego on 20 November.

[1] On 22 January 1982, Ajax got underway for training and a brief port visit to Mazatlan, Mexico, and arrived back home on the last day of the month.

Pre-overseas movement preparations throughout the next few months ensured that the repair ship was ready for her 2 April departure for the western Pacific and the Indian Ocean.

Over the next seven months, the ship provided repair services for units of the Pacific Fleet at San Diego, served as a training facility for naval reserve detachments undergoing their annual two weeks of active duty, and made preparations for a regular overhaul.

On 1 and 2 March, she put to sea to conduct post-overhaul trials and, on the 3rd, resumed repair services to other units of the Pacific Fleet.

During the last week in March, she was frequently at sea in the local operating area carrying out independent ship's exercises.

Except for two periods at sea in October for refresher training, Ajax spent the rest of 1984 in port repairing ships of the Pacific Fleet.

After conducting availabilities for ships of the Middle East Force at Al Masirah from 22 November to 5 December, she put to sea to avoid a large dust storm.