Thorn was laid down on 15 November 1942 at Kearny, New Jersey, by the Federal Shipbuilding and Drydock Co.; sponsored by Mrs. Beatrice Fox Palmer and launched on 28 February 1943.

On her last convoy run, she escorted two oilers to Ponta Delgada, in the Azores, in company with Stockton — the first ships to enter the port under the terms of the new agreement between the Allies and the government of Portugal.

Lt. James P. Drake, USNR, and Boatswain's Mate, First Class, E. Wells were awarded Navy and Marine Corps Medals for their bravery in the rescue of three Turner survivors, and three other men received commendation bars for their part in the operation.

Thorn moved directly from there to Cape Sudest where, on 4 March, the destroyer embarked troops and supplies of the Army's 7th Cavalry and immediately proceeded to Los Negros Island for the invasion of the Admiralties.

On 10 April — while making a practice torpedo run during preparations for forthcoming Allied landings at Hollandia — Thorn struck an uncharted reef.

As American forces massed for the initial assaults on the Japanese-occupied Philippine Islands, Thorn joined the fire support screen for TF 77.

At dawn on 21 October, Thorn's gunners opened fire on a Japanese Aichi D3A and sent the enemy dive bomber splashing into the sea near the transport area.

On the evening of 25 October, Thorn's division received orders to lie-to off Homonhon Island, on the east side of Leyte Gulf, to conduct a torpedo attack on a Japanese force expected from the eastward.

Ordered to Ulithi, Thorn departed Philippine waters to rejoin the U.S. Third Fleet in the Carolines, for duty with the Fast Carrier Task Force (then designated TF38).

While returning to the Carolines, via Leyte Gulf and the Mindoro Strait, Thorn rescued the crew of a downed TBM and the pilot of a crashed fighter before arriving at Ulithi on 27 January.

On 21 February, Thorn and Ute learned that the escort carrier Bismarck Sea had been struck by two Japanese kamikazes, and they rushed to aid the stricken ship.

Two days in Ulithi followed the ship's return, and, on 13 March, Thorn reformed with the U.S. 5th Fleet support group built around the cruiser Detroit for the Ryūkyū operations.

On the second run, Thorn observed two enemy planes splashing into the sea, victims of combat air patrol (CAP) fighters and ship gunfire.

Streaming her homeward-bound pennant, Thorn, in company with DesRon 19, steamed out of Tokyo Bay on 8 October and joined the battleships Tennessee and California off Wakayama the following day.