Joining the Pacific Fleet in late 1937, Mugford conducted local operations along the West Coast and around the Hawaiian Islands, taking time out for periodic overhauls and upkeep. 7 December 1941 found her at Pearl Harbor. When the attack began, Mugford was on standby status and while raising steam to get underway, she downed three planes in 10 minutes with her antiaircraft guns. Within an hour after the attack began, the “little ship” was steaming out of Pearl Harbor firing as she went. Her next major duty was to screen the Wake Island relief force and after completion of this duty served as an escort for convoys traveling between the United States and Australia. She served in this capacity until mid-1942.

On 7 August Mugford was on patrol off Lunga Point, Guadalcanal, when a large Japanese airstrike came in; three near misses and one bomb hit couldn’t prevent Mugford from downing two of her attackers, but she suffered eight killed, 17 wounded and 10 missing. Next day she shot down another enemy aircraft in a raid in which she suffered no damage, and rescued two enemy aviators from the water. On the 9th, she sped toward the action of the first Battle of Savo Island, arriving in time to pull 400 survivors of Vincennes (CA-44) and Astoria (CA-34) from the water.

After battle damage repairs at Sydney, from 18 September through December, she operated on patrol in the Coral Sea and along Australia’s northern coast. Brisbane was her base for continued patrol, as well as escort missions to Milne Bay, New Guinea, which became her base later in the summer as New Guinea operations took on a faster pace. She joined in the assault on Woodlark Island in July, conducted shore bombardment and patrols in that general area in August, and in September escorted LSTs to the invasion of Lae on the 4th, after which she patrolled offshore while under enemy air attack. Later that month she conducted pre-invasion bombardment north of Finschhafen, off which she served until late in October. On 20 October, she and four companion destroyers were attacked by 60 enemy planes; Mugford suffered no damage. (continued)