The first Mercy (AH-4) was built in 1907 as Saratoga by William Cramp and Sons, Philadelphia, Pennsylvania, for the Ward Line, New York, New York. After use as a US Army troop transport during the first nine months of World War I, she was purchased by the US Navy from the US War Department[?] on 27 September 1917. On 30 October 1917, she began conversion to a hospital ship at the New York Navy Yard, Brooklyn, New York, and was commissioned USS Mercy on 24 January 1918.
Assigned to the Atlantic Fleet, Mercy operated in the Chesapeake Bay area with Yorktown, Virginia, as her home port, attending the war wounded and transporting them from ships to shore hospitals. In October 1918 she sailed for New York to join the Cruiser and Transport Service. On 3 November the hospital ship departed New York on the first of four round trips to France, returning 1,977 casualties by 25 March 1919.
For most of the next 15 years following World War I, Mercy served off the east coast with Philadelphia, Pennsylvania, as her home yard. From 1 December 1924, until 1 September 1925, she was in reserve at the Philadelphia Navy Yard. On 25 November the hospital ship went into reduced commission, returning to full commission 1 September 1926. Mercy remained in commission until loaned to the Philadelphia branch of the US Public Relief Adminstration[?] 23 March 1934.
The second Mercy (AH-8) was a Comfort-class hospital ship[?] laid down under Maritime Commission contract by Consolidated Steel Corporation at the Wilmington Yard, Wilmington, California[?], on 4 February 1943. She was acquired by the US Navy from the Maritime Commission on 25 March 1943 and launched the same day, sponsored by Lieutenant (junior grade) Doris M. Yetter, NC, USN, who had been a prisoner of war on Guam in 1941. She was converted from a cargo ship to a hospital ship by Los Angeles Shipbuilding & Drydock Company, San Pedro, California and commissioned 7 August 1944, with Captain Thomas A. Esling, USNR, in command.
After shakedown beginning 17 August, Mercy, staffed by the US Army's 214th Hospital Ship personnel, was assigned to NTS to operate with the 5th and 7th Fleets. She departed San Pedro 31 August for the South Pacific and, after calls at Pearl Harbor and Eniwetok, arrived Hollandia, New Guinea[?], 14 October. Five days later the hospital ship departed for the Philippines for the initial landing at Leyte on 20 October, arriving off Leyte Gulf the morning of 25 October to find the Battle for Leyte Gulf[?] still raging for another day.
Mercy moved to San Pedro Bay[?] later the same day and began embarking some 400 casualties, mostly from LSTs alongside. On 26 October she sailed for the Admiralties[?], via Kossol Roads, Palaus, Carolines[?], arriving at Manus[?] to disembark the wounded for transfer to base hospitals. During the next five months, Mercy completed seven more voyages from Leyte to Manus, or Hollandia. She also transported the 3d Field Hospital from New Guinea to Tacloban, Philippines[?], early in January 1945.
On 19 March Mercy reported to the 5th Fleet at Ulithi, Carolines[?], for service during the Okinawa campaign, beginning with the landings 1 April. She arrived off Okinawa the morning of 19 April in company with Solace (AH-5)[?] to remain for four days at Hagushi Beach[?] embarking patients despite frequent air raids and threat of kamikazes. The hospital ship then got underway for Saipan, Marianas[?], 23 April. She made two more voyages to Okinawa, returning from the latter to Saipan 24 May.
Mercy next carried wounded from Leyte and Manila on two voyages to Biak, Schouten Islands[?], returning to Manila on 23 June for two months' duty as station hospital ship. On 19 August she embarked the 227th Station Hospital assigned to the Korean Occupation Forces[?], and three days later departed for Korea via Okinawa, arriving Jinsen[?] 9 September.
On 19 October the hospital ship departed for Manila and San Pedro, California, arriving 14 November. She got underway for the central Pacific 4 February 1946, arriving Pearl Harbor on12 February for duty until 2 April when she returned to California.
Mercy decommissioned at San Francisco, California, 17 May, was delivered to the War Department the same day, and transferred to the US Army 20 June for further service as a hospital ship. On 25 September 1946, she was struck from the Naval Vessel Register.
Mercy received two battle stars for her World War II service.