Ardent was originally laid down as HMS Buffalo (BAM-8), for the Royal Navy on 20 February 1943 at Alameda, California, by the General Engineering & Drydock Co.; rescheduled for delivery to the United States Navy; renamed Ardent and redesignated AM-340 on 24 May 1943; launched on 22 June 1943; sponsored by Mrs. Bernadette Armes, the daughter-in-law of George A. Armes, President of the General Engineering & Drydock Co., and commissioned on 25 May 1944.

During the first seven months of her career, Ardent escorted convoys and ships operating between the west coast of the United States and the Hawaiian Islands, though she also ranged as far as Eniwetok in the Marshalls and Tarawa in the Gilberts.

Rockford left her escort station to assist, and fired her first barrage of rockets from her "Hedgehog" at 13:08; two explosions followed, before an underwater detonation rocked the ship.

She reached Pearl Harbor on the 10th and underwent an intensive training period before sailing for the Marshall Islands on 27 January 1945 with Task Group (TG) 51.11, arriving on 5 February at Eniwetok.

She conducted mine-sweeping operations off that island during the day from 15 to 18 February, and each night, her group retired to screen USS Estes (AGC-12).

On 19 February, Ardent took bomb-damaged USS Blessman (DE-69) in tow and proceeded to the Marianas as escort for a convoy of damaged LCIs.

Ardent opened fire on the third aircraft, and saw it splash, the victim of a barrage put up by a formation of ships on the starboard quarter.

On L-day, the day of the landings at Okinawa, 1 April 1945, a suicider crashed the nearby USS Adams (DM-27), causing extensive damage.

Six days later, on the 13th, the minesweeper sailed for Pearl Harbor, and was at sea, en route to the Hawaiian Islands, when the war with Japan ended.

During her time at Okinawa, she sortied on 7 October to ride out a typhoon, and conducted sweeps down the island's east coast for survivors of that storm.

Joining TU 52.4.1 on 27 October, Ardent proceeded to the "Klondike" minefield area, located in the East China Sea 100 miles (160 km) southwest of Kyūshū.

Returning to pier 17, Treasure Island (California), on 15 December 1946, to commence preparations for inactivation, Ardent shifted to the San Diego Naval Station on 22 January 1947.