After shakedown along the California coast, Gwin sailed for the Pacific theatre as flagship of Mine Squadron 3, reaching Pearl Harbor 3 January 1945. A week later, the squadron left for the fighting front. At Saipan on 20 January, Gwin and her sister [minelayers] joined Battleship Division 7. For seven days, 21 to 26 January, she participated in the preliminary bombardment of Iwo Jima, the next to the last step in America’s long island-hopping campaign across the Pacific. Returning to Pearl Harbor, Gwin underwent overhaul before sailing for Eniwetok on 23 February.

From Eniwetok, Gwin steamed to the Nansei Shoto on 17 March to sweep the area around Okinawa, the scene of one of the war’s bloodiest and most heroic invasions. Acting in a variety of roles—antisubmarine screen, radar picket ship, minesweeper and fire support—Gwin [remained] off Okinawa the following five months, almost to the very end of the war. During this period, she accounted for some 16 enemy aircraft as the Japanese launched their desperate kamikaze attacks. Nine of these Japanese planes fell victim to Gwin’s guns on only two days, 16 April and 4 May. An air raid 16 April saw Gwin down two “Betties,” Japanese dive bombers, coming in only to have another come sweeping in and crash in the sea some 25 yards as the agile DM evaded her. And then the alert gun crew swung their battery to catch another Japanese plane and shoot it down less than 50 yards from the ship.

At dusk on 4 May, Gwin was on a radar picket station off Okinawa. Combat Air Patrol reported 8 to 10 enemy planes to port and Gwin swung her batteries to face the enemy. Suddenly, a second contingent of planes swept in out of the setting sun to starboard! Gwin swung her guns around just in time, and two of the attackers splashed into the sea. Whirling to port, the gun crews fired into the original attack group and accounted for three more kamikazes. The seas had not yet closed over these three planes when a sixth, another kamikaze, crashed Gwin. Two men were killed, 2 missing, and 11 injured as the suicide plane embedded itself into Gwin’s after 40mm platform. Then, as damage control parties rushed to quell the fires raging around the kamikaze, the Japanese attack ended as suddenly as it had begun. In less than six hectic, heroic minutes, Gwin, although under attack from all quarters, had downed five Japanese planes and been herself damaged by a sixth.

After a brief stay at [Kerama Retto] for battle damage repairs, Gwin returned to patrol and sweeping duties around Okinawa. She rendezvoused on 20 August with Task Force 3S and, with such illustrious fighting ships as Missouri, Lexington, Yorktown, and Shangri-La, headed for Tokyo Bay. Putting into Sagami Bay 27 August 1945, Gwin began to sweep the area, front door to Tokyo Bay, and destroyed some 41 mines in 2 days’ duty. At last, on 29 August 1945, she steamed into Tokyo Bay and anchored under the towering snowcap of Mount [Fuji]. Departing for Okinawa on 1 September, Gwin remained on minesweeping duty there and in the East China Sea for the rest of the year.

With her share of the Pacific “mopping-up” complete, Gwin at last headed home, reaching San Pedro, California on 23 February 1946. The battle-tested ship then sailed for Charleston, South Carolina, arriving on 14 March. Gwin decommissioned there on 3 September 1946 and was placed in reserve.

As the Korean War necessitated the strengthening of America’s fleet, Gwin recommissioned at Charleston on 8 July 1952, Comdr. R. E. Oliver in command. For the next few years she divided her time between Caribbean and local exercises, European cruises and NATO maneuvers, with time out for overhaul. In 1953, Gwin crossed the Atlantic for a four-month tour of duty with the Sixth Fleet, visiting 10 Mediterranean ports before returning to Charleston on 3 February 1954. Midshipman Able Cruises June to August 1954 and 1955 took her to Lisbon, Portugal, Le Havre, Valencia, Spain and Torquay, England. Gwin returned to the Mediterranean a final time in 1957 for NATO maneuvers with ships of the Portuguese, French and British navies, visiting both Brest and Gibraltar.

In between Caribbean and Mediterranean cruises and training, Gwin engaged in a variety of minesweeping and hunter-killer antisubmarine exercises along the East Coast and participated in several other NATO maneuvers in American waters. Gwin sailed to the Philadelphia Navy Yard on 12 January 1958 where she decommissioned on 3 April 1958 and remains in reserve through 1967.

Gwin received the Navy Unit Commendation and four battle stars for service in World War II.