In March 1941, Rear Admiral Giffen became commander of a cruiser division. He led the North Atlantic Neutrality Patrol on increasingly "warlike" operations during the latter part of 1941. Once war formally began for the United States in December, he commanded surface forces that escorted convoys and, at times, operated with the British Home Fleet. In November 1942, he participated in the North Africa invasion, during which his task force actively engaged French warships and aircraft off Casablanca, Morocco.