After undergoing availability early in 1944, "Harold C. Thomas" sailed as flagship for Escort Division 10, on 29 February. Reaching Eniwetok, Marshall Islands, on 11 March, she did escort work until 30 March when she became part of a hunter-killer carrier group on anti-submarine patrol east of the Marshalls. Returning to Pearl Harbor on 6 May, the destroyer escort spent the remainder of the year in the vital but unsung work of shepherding merchantmen, cargo ships, and transports through the back staging area, up to their assembly points for invasion forces. This duty took "Harold C. Thomas" to the Marshall, Admiralty, Palau, and Marianas Islands. She also performed some submarine training work at Pearl Harbor. On 21 November "Harold C. Thomas" rescued seven men from a PBM flying boat which had crashed at sea off Majuro Atoll.