Cape Carthage was laid down under a Maritime Commission contract (MC hull 304) on 5 June 1943 by Pusey & Jones Corp., Wilmington, Del.

; launched on 12 October 1943; sponsored by Mrs. J. H. Deinlein; acquired by the Navy on 22 December 1943; renamed Acontius and designated AGP-12; converted for naval service at Baltimore, Md., by the Maryland Drydock Co.; and commissioned on 23 June 1944, Lt. Comdr.

Following shakedown out of Guantanamo Bay, Cuba, Acontius steamed to the coast of Panama, transited the canal, and arrived at Tulagi, Solomon Islands, on 18 September.

In August, the tender became the flagship for Commander, Motor Torpedo Boat Squadrons, Pacific Fleet, Commodore Richard W. Bates.

After Japan formally surrendered on 2 September, Acontius moved to Guinan anchorage, Samar, and there became involved in the inactivation of PT boats.