She was the second Navy ship named after Lieutenant (junior grade) Richard Bull (1914–1942), a naval aviator who was posthumously awarded the Distinguished Flying Cross.

Following her shakedown training out of Bermuda, Bull escorted the Army transport USAT George Washington to Norfolk, Virginia, and then continued on to Boston, Massachusetts, where she arrived on 4 October 1943 for post-shakedown availability.

The destroyer escort touched briefly at New York City; proceeded thence to Curaçao, in the Dutch West Indies, and then headed across the Atlantic to Derry, Northern Ireland, on her first convoy-escort mission.

Following her return to New York on 9 December, Bull operated out of Cape Cod Bay through the end of 1943 with Fleet Air, Atlantic, towing targets used by Navy planes practicing radar and dive-bombing tactics.

While the destroyer escort battled her way through a hurricane on 3 February, ammunition tumbled from storage racks that had been torn loose by the storm and caused a few anxious moments before it was battened down.

High winds and heavy seas also loosened the grips holding the ship's motor whaleboat in place and jostled the foremast so much so that it required a strengthening jury rig.

Following an availability at New York, Bull conducted refresher training out of Casco Bay, Maine, before proceeding to Boston to pick up another transatlantic convoy.

After an availability at the New York Navy Yard, she escorted one additional convoy to England between 12 and 23 May, and remained in the British Isles with the naval forces gathering for the cross-channel invasion of France.

While retiring from Lingayen Gulf to Leyte as part of Task Unit 77.15.5 (TU 77.15.5), Bull watched an American plane crash on nearby Siguijori Island thought to be occupied by the Japanese.

Detached to rescue the pilot, Bull, guided by two Vought F4Us, proceeded to the area and found the plane 50 yards (46 m) off the beach on the northwest side of the island.

Sending armed landing parties in two of her boats, Bull soon spotted crowds of native Filipinos coming out to greet the American sailors.

Bull took part in the reconnaissance of both preferred and alternate beaches and drew Japanese fire several times, yet she escaped without damage on each occasion, despite several near misses.

Leaving Iwo Jima on 5 March, Bull headed for Ulithi to make ready for the next major American amphibious assault: the invasion of Okinawa.

Continuing thence via Eniwetok and Pearl Harbor, the fast transport reached San Pedro, California, where she conducted voyage repairs, refresher training, and UDT rehearsals for the invasion of the Japan.