Gwin completed shakedown training 25 April 1941 and underwent final alterations in the Boston Navy Yard before conducting neutrality patrol throughout the Caribbean Sea. On 28 September 1941 she assumed identical service in the North Atlantic from her base at Hvalfjordur, Iceland. After the infamous raid on Pearl Harbor, she hurried back to the Eastern Seaboard thence through the Panama Canal to San Francisco, Calif.
On 3 April 1942 Gwin stood out of San Francisco Bay as a unit of the escort for carrier Hornet who carried 16 Army B-25 bombers to be launched in a bombing raid on Tokyo. Admiral William “Bull” Halsey in carrier Enterprise rendezvoused with the task force off Midway, and Lt. Col. “Jimmy” Doolittle’s famed raiders launched the morning of 18 April when some 600 miles east of Tokyo. The task force made a rapid retirement to Pearl Harbor, then sped south 30 April 1942, hoping to assist carriers Yorktown and Lexington in the Battle of the Coral Sea. That battle concluded before the task force arrived, and Gwin returned to Pearl Harbor 21 May for day and night preparations to meet the Japanese in the crucial battle for Midway Atoll.
Gwin departed Pearl Harbor 23 May 1942 with Marine reinforcements for Midway and returned to port 1 June. Two days later she raced to join the Fast Carrier Task Force searching for the approaching Japanese Fleet off Midway. But the crucial battle was all but concluded by the time she arrived on the scene 5 June 1942. Four large Japanese aircraft carriers and a cruiser rested at the bottom of the sea along with some 250 enemy planes and a high percentage of Japan’s most highly trained and experienced carrier pilots. The Island of Midway was saved to become an important base for operations in the western Pacific. Likewise saved, was Hawaii, the great bastion from which attacks were carried into the South Pacific and Japan itself. But there were American losses too. Gwin sent a salvage party to assist in attempts to save carrier Yorktown (CV-5), heavily damaged by two bomb and two torpedo hits in the Battle of Midway. As attempts continued 6 June 1942, a Japanese submarine rocked Yorktown with torpedo hits and sank destroyer Hammann who was secured alongside the carrier. The salvage party had to abandon Yorktown and surviving men were rescued from the sea. The carrier capsized and sank the morning of 7 June 1942. Gwin carried 162 survivors of the two ships to Pearl Harbor, arriving 10 June 1942.
Gwin departed Pearl Harbor 15 July 1942 to operate in the screen of fast carriers who pounded Japanese installations, troop concentrations and supply dumps as Marines invaded Guadalcanal in the Solomons 7 August 1942. In the following months Gwin convoyed supply and troop reinforcements to Guadalcanal. Joining a cruiser-destroyer task force, she patrolled the “Slot” of water between the chain of Solomon Islands to intercept the “Tokyo Express” runs of enemy supply, troop and warships supporting Japanese bases in the Solomons.
On 13 November 1942, Gwin and three other destroyers formed with battleships Washington and South Dakota to intercept an enemy bombardment-transport force approaching the Solomons. The following night the task group found the enemy of Savo Island: battleship Kirishima, 4 cruisers, 11 destroyers, and 4 transports. The Naval Battle of Guadalcanal was hot and furious. Gwin found herself in a private gun duel with cruiser Nagara and four destroyers. She took a shell hit in her engine room. Another shell struck her fantail and enemy torpedoes began to boil around the destroyers.
Though shaken by exploding depth charges Gwin continued to fire at the enemy as long as any remained within range. In a short time the other three American destroyers were out of action, two sinking and Benham surviving with her bow partially destroyed. But a masterful battleship duel fought by South Dakota and Washington wrecked Japanese battleship Kirishima. She had to be abandoned and scuttled as was Japanese destroyer Ayanami. The battle was over. The gallant American ships had saved Guadalcanal from a savage bombardment in this naval action that marked a turning point toward victory for U.S. forces in the Solomons.
Gwin attempted to escort the noseless Benham to Espiritu Santo, New Hebrides Islands. But when all hope was lost, survivors transferred to Gwin who hurried Benham’s abandoned hulk to the bottom with gunfire. The survivors were landed 20 November at Nouméa, New Caledonia, and Gwin was routed onward to Hawaii, thence to the Mare Island Navy Yard, arriving 19 December 1942.
Having been overhauled, Gwin returned to the Southwest Pacific 7 April 1943 to escort troop reinforcements and supplies throughout the Solomons. On 30 June she served with the massive amphibious assault force converging on New Georgia under the leadership of Rear Admiral Richmond Kelly Turner. She supported the most important landings 30 June on the north coast of Rendova Island, 5 miles across Blanche Channel from Munda.
Immediately after the first wave of troops hit Rendova Beach, Munda Island shore batteries opened fire on the four destroyers patrolling Blanche Channel. Gwin was straddled by the first salvo. A moment later a shell crashed her main deck aft, killing three men, wounding seven and stopped her after engine. The half-dozen enemy shore batteries were soon silenced as Gwin laid down an effective heavy smokescreen to protect the unloading transports. When aerial raiders appeared, her gunners shot down three. Rendova Island was soon in American possession. It served as an important motor torpedo boat base to harass Japanese barge lines and a base for air support in the Solomons.
Gwin escorted a reinforcement echelon from Guadalcanal to Rendova, then raced out in to the “Slot” 7 July to rescue 87 survivors of cruiser Helena, lost in the Battle of Kula Gulf. She then joined a cruiser-destroyer task force under Rear Admiral Walden L. Ainsworth to head off a formidable “Tokyo Express” headed through the Solomon Islands to land troops at Vila. The battle was joined past midnight of 12–13 July and Japanese cruiser Jintsu quickly slid to the bottom, the victim of smothering gunfire and torpedo hits. But four Japanese destroyers, waiting for a calculated moment when Ainsworth’s formation would turn, launched 31 torpedoes at the American formation. His flagship Honolulu, cruiser St. Louis and Gwin, maneuvering to bring their main batteries to bear on the enemy, turned right into the path of the deadly “long lance” torpedoes. Both cruisers received damaging hits but survived. Gwin was not so fortunate. She received a torpedo hit amidships in her engine room and exploded in n burning white heat—a terrible sight. Destroyer Ralph Talbot took off Gwin’s crew after their heroic damage control efforts failed and she had to be scuttled. Two officers and 59 men perished with the gallant destroyer, casualties of the Battle of Kolombangara.
Gwin received five battle stars for service in World War II.
Naval History & Heritage Command including Dictionary of American Naval Fighting Ships.