Convoy success meant delivery, not submarine kills

MAC ships sailed with their assigned convoys to close the Atlantic air gap and protect the flow of troops, fuel, food, and equipment. Their patrol aircraft always knew where the convoy was and could search its approaches faster than a submarine could reposition to attack. Surface-search radar threatened even a raised periscope and forced U-boats underwater, where slower movement, limited oxygen, and dependence on a finite torpedo load reduced their freedom of action. The important measure was therefore not submarines destroyed but merchant ships delivered. A convoy that reached port without encountering the enemy was a complete operational success, even if its escorts recorded no kill.