Her shakedown cruise took her to the Caribbean and South America and she remained in the Atlantic area until mid-1937. Transferred to the Pacific, Mahan took part in the fleet program of training exercises and large-scale fleet problems.
Assigned to DesRon 5, Mahan was at sea with Lexington’s Task Force 12, delivering Marine scout bombers to Midway Island, when the Japanese attacked Pearl Harbor on 7 December 1941. Over the next ten months, she operated in escort and patrol duties off Hawaii and the west coast, then headed west to join the Guadalcanal campaign in October 1942. En route, with Lamson, she sank two Japanese patrol boats south of the Gilbert Islands.
Mahan was part of Enterprise‘s screen with battleship South Dakota, heavy cruiser Portland, anti-aircraft cruiser San Juan and destroyers Porter (DesRon 5 flagship), Conyngham, Shaw, Cushing, Smith, Preston and Maury during the Battle of the Santa Cruz Islands, after which she collided with South Dakota during a submarine alarm, with both ships sustaining heavy damage.
After receiving a replacement bow at Pearl Harbor, Mahan resumed escorting convoys from January 1943 before joining the Seventh Fleet at the beginning of July. Operating initially from Milne Bay, New Guinea, she supported landings at Nassau Bay, Lae and Finschhafen, then Cape Gloucester, New Georgia, in December and Los Negros in the Admiralty Islands, February 1944.
Pausing for a west coast overhaul beginning in July, Mahan returned to the Seventh Fleet in October. Assigned to picket duty during landings at Ormoc Bay on Leyte’s west coast, on the morning of 7 December 1944, she was patrolling between Leyte and Ponson Island when about twelve Japanese bombers attacked. Working up to 34 knots, Mahan shot down three, but three others dove into her in quick succession. As her skipper turned her toward other vessels of the picket line (including destroyer Ward, lost in the same attack), her high speed helped fan her fires out of control, preventing access to valves for flooding her magazines. The ship was abandoned and the survivors, including 32 wounded but excluding ten killed or missing in action, were picked up by Lamson and Walke (DD 723), which was then ordered to sink her by gunfire and torpedoes.
Mahan earned five battle stars for her service in World War II.
Sources: 1. Morison, Vol 12; Roscoe