Mid-Ocean Escort Force (MOEF) referred to the organisation of anti-submarine escorts for World War II trade convoys between Canada and Newfoundland, and the British Isles. The allocation of United States, British and Canadian escorts to these convoys reflected preferences of the United States upon United States' declaration of war and the organisation persisted through the winter of 1942–43 despite withdrawal of United States ships from the escort groups. By the summer of 1943, United States Atlantic escorts were focused on the faster CU convoys and the UG convoys between Chesapeake Bay and the Mediterranean Sea; and only British and Canadian escorts remained on the HX, SC and ON convoys.
HMCS Sackville, preserved at Halifax Harbour, is believed to be the only survivor of the MOEF Flower-class corvettes
United States Coast Guard cutter Ingham, shown here in a post-war configuration, is one of the few larger MOEF escorts to be preserved
USS Reuben James was sunk while escorting convoy HX 156
USS Benson was one of the modern United States destroyers initially assigned to MOEF and later diverted to escort troop convoys
An Escort Group consisted of several small warships organized and trained to operate together protecting trade convoys. Escort groups were a World War II tactical innovation in anti-submarine warfare by the Royal Navy to combat the threat of the Kriegsmarine's "wolfpack" tactics. Early escort groups often contained destroyers, sloops, naval trawlers and, later, corvettes of differing specifications lacking the ability to maneuver together as a flotilla of similar warships, but rigorously trained in anti-submarine tactics to use teamwork emphasizing the unique sensors, weapons, speed, and turning radius of each ship. The development of these 'escort groups' proved an effective means of defending shipping convoys through the Battle of the Atlantic.
HMS Skate was one of the oldest destroyers in the Royal Navy when assigned convoy protection duty for the Western Approaches Command.
HMS Keppel was a World War I flotilla leader.
Town-class destroyers received in the Destroyers for Bases Agreement were widely distributed among the escort groups.
HMS Amazon was a unique prototype.