"Gunnel"s first war patrol (19 October – 7 December 1942) covered a passage from the United States to the United Kingdom, during which she participated in Operation "Torch", the Allied invasion of North Africa. One of six submarines assigned to Admiral Henry K. Hewitt's Western Naval Task Force, "Gunnel" did reconnaissance off Fedhala 6 November 1942, 2 days before the invasion, and on D-day (8 November) made infrared signals to guide the approaching fleet to the beachheads. Missions well accomplished, the submarine departed for Rosneath, Scotland, 7 December to terminate her first patrol. "En route" home, the drive gears of her HOR engines failed, forcing her to complete the final on her auxiliary diesel, leading to a major overhaul at Portsmouth Naval Shipyard in Kittery, Maine.