Battle of the Atlantic

Stern held her shakedown cruise off Bermuda and returned to New York for post-shakedown availability. After a short training period off Casco Bay, Maine, she escorted a convoy to Ireland and returned with another to New York. She stood out of that port, on 23 March 1944, with a convoy for North Africa and arrived at Casablanca on 2 April. On 7 May, she sailed for home with a return convoy and arrived at New York on the 17th. Stern made another round trip to Ireland, via Bermuda from 8 June to 2 August, and one more to Bizerte, Tunisia, which ended in New York on 7 October.

Pacific War

Stern sailed for the West Coast on 23 October and arrived at San Diego, California, on 10 November. Routed westward, she arrived at Pearl Harbor on 23 November, and after calling at the Marshall Islands, arrived at Ulithi, Caroline Islands, on 12 December. She was assigned to the at-sea logistics group (Task Group 30.8) of the U.S. 3rd Fleet. Stern operated with the 3rd Fleet from 16 to 25 December and from 29 December 1944 to 28 January 1945, supporting operations liberating Luzon. The ship returned to Ulithi on 8 February and was attached to the screen of the attack transport group of the task force, which would invade Iwo Jima. The force arrived off that island early on the morning of the 19th, and the assault groups began landing under intense hostile fire. From that morning until 1 March, the escort protected American transports off Iwo Jima.

On that day, Stern was routed via Guam to the Philippine Islands. She arrived there on 8 March, was assigned to the screen of Task Group 51.1, the Western Islands Attack Group, and sailed for the Ryukyu Islands on 21 March.

Stern screened the attack transports heading for Kerama Retto and arrived there on 26 March. She then performed antisubmarine duty off the islands until 5 April, when she was ordered to escort a resupply convoy to Guam. From there, she sailed to Leyte to join another Okinawa-bound task unit and was back off the island on 18 April. This tour of Okinawa was unbroken until July. On 13 and 18 May, she shot down two enemy planes each day, and splashed a single one on the 27th.

On 1 July, Stern sailed for the West Coast of the United States, via Ulithi and Pearl Harbor. She arrived at San Pedro, Los Angeles, on the 25th. She sailed from that port on 20 October and proceeded, via the Panama Canal, to Norfolk, Virginia, for inactivation. By a directive issued in March 1946, Stern was to be sold as surplus to naval requirements. The sale was cancelled, and the escort was transferred to the Atlantic Reserve Fleet. She was placed in reserve, out of commission, on 26 April 1946 and berthed at Green Cove Springs, Florida.