Commissioned an Ensign on 10 September, he joined Bombing Squadron 6 (VB-6, based on the USS Enterprise (CV-6) and flew Douglas SBD Dauntless dive bombers until early in December 1941.

[2] After fitting-out at Houston and loading ammunition at the San Jacinto Ordnance Depot, Willis departed Galveston, Texas, on 5 January 1944 in company with USS Kretchmer (DE-329) bound for the British West Indies and reached Bermuda on the 10th.

Two days later, Willis then proceeded-in company with USS Stewart (DE-238) to Staten Island, New York, and, upon arrival, reported for duty to Commander, Escort Division (CortDiv) 51.

That day, the task group put to sea for operations in the Central Atlantic that took its ships first to Casablanca-visited from 18 to 22 March-and then to the British West Indies in mid-April.

They scored their first success on 13 March when Hobson teamed with Haverfield, planes from Bogue's Composite Squadron (VC) 95, HMCS Prince Rupert, and British aircraft to sink U-575.

On 24 June, 800 miles (1,300 km) southwest of the Azores, TG 22.2 destroyed another Axis submersible when planes of Bogue's VC-69 sank the Japanese submarine I-52.

The destroyer escort then underwent repairs at Bayonne, New Jersey, from 4 to 14 July, after which time she joined CortDiv 51 for a period of refresher training out of Casco Bay, Maine.

Proceeding back to Hampton Roads upon completion of those training evolutions, Willis moored at the Naval Operating Base (NOB), Norfolk, Va., on 22 July.

The group conducted antisubmarine warfare (ASW) training exercises and gunnery drills en route to Bermuda and arrived there on 29 July.

The radio operator on duty in Willis was subsequently commended for his action that enabled a lost aircraft and her crew to reach home safely.

Shortly before she left the yard to shift to Pier 92, New York, on 28 November 1944, the ship received the Presidential Unit Citation "for outstanding performance in combat as an escort vessel in two task groups with USS Bogue during the periods: 26 February to 19 April 1944, and 4 May to 3 July 1944."

Willis planeguarded for Bogue in the carrier qualification areas off Quonset Point and Narragansett Bay before the destroyer escort put into the New York Navy Yard for availability.

After another brief, unscheduled availability-this time at the Boston Navy Yard, Willis again resumed training in Casco Bay before she shifted south to conduct ASW exercises out of New London.

Underway again two days later, the destroyer escort shifted north, honing her ASW skills in exercises conducted in company with Bogue off the coast of Rhode Island, putting into Melville, R.I., in mid-April.

On 16 April, Willis cleared Melville as part of TG 22.3 to conduct hunter-killer operations-known as Operation "Teardrop"-on "barrier patrol" to prevent the penetration of U-boats to the east coast of the United States.

On 30 April Willis, in company with Swenning, TU 22.7.1 and TG 22.8, left the screen of the task group to investigate a disappearing radar contact reported by aircraft from USS Core (CVE-13).

Upon completion of the repairs, Willis, now earmarked for service in the Pacific, a theater of war-underwent a month-long availability at the Norfolk Navy Yard before sailing for Guantanamo Bay, Cuba to conduct refresher training.