Trials, fitting out, shakedown and minor repairs occupied Fanning until 22 April 1938, when she joined Philadelphia (CL-41) at Annapolis to escort the cruiser as she carried President Franklin D. Roosevelt on a Caribbean cruise. After returning to New York on 11 May, she underwent overhaul, escorted MS Kungsholm with the Crown Prince of Sweden embarked, then sailed for the West Coast to join the Battle Force in September. Based on San Diego the destroyer conducted antiaircraft gunnery, antisubmarine and tactical exercises. Over the next 3 years, Fanning’s schedule took her back to the Atlantic once and to Hawaii several times, all the while enhancing her battle readiness.
The attack on Pearl Harbor on 7 December 1941 found Fanning at sea with TF 8 returning to Pearl Harbor from Wake Island where Enterprise (CV-6) had delivered the squadron of Marine Corps fighter planes, which became Wake’s only airborne defense. The force made a vain search for the enemy, refueled at Pearl Harbor on 8 December, and the following day sortied to hunt enemy submarines. They made several contacts, but aircraft from Enterprise scored the lone success in sinking I-170 on 10 December in 23° 45’ N., 155° 35 W. (continued)