The formal entrance of the United States into World War II lengthened her convoy assignment beyond the western Atlantic Ocean. Escort of slow merchant convoys out of Boston gave way in summer 1942 to duty with fast troop transports out of New York City. U-boats and bad weather were not the only dangers to be encountered. When caught fire 3 September, "Mayo" swiftly moved alongside the burning ship and removed 247 survivors. With the invasion of North Africa, "Mayo" appeared at Casablanca, Morocco, 12 November, 4 days after D‑Day, to protect the landing of reinforcements. A retraining period at the end of the year in Casco Bay, Maine, temporarily interrupted convoy assignments.