Upon her return to the east coast, "Wainwright" resumed her patrols. Her assignment, however, took on a new complexion. No longer simply trying to prevent the spread of hostilities to the Western Hemisphere, she patrolled instead to protect America's shorelines and seagoing traffic along her coast from Germany's undersea fleet. That duty continued until mid-March 1942, when the warship received orders to join the British Home Fleet as part of an American force composed of , , , , , and seven other destroyers. On 25 March, she departed Casco Bay, Maine, in company with "Wasp", "Washington", "Wichita", "Tuscaloosa" and the destroyers of Destroyer Squadron 8 (DesRon 8), with Commander DesRon 8 (ComDesRon 8) embarked. (This US Navy involvement allowed the Royal Navy to release ships for the invasion of Madagascar.) The task unit reached Scapa Flow, in the Orkney Islands north of the British Isles, on 3 April.