Convoy SC 121

As western Atlantic coastal convoys brought an end to the second happy time, Admiral Karl Dönitz, the Befehlshaber der U-Boote (BdU) or commander in chief of U-Boats, shifted focus to the mid-Atlantic to avoid aircraft patrols. Although convoy routing was less predictable in the mid-ocean, Dönitz anticipated that the increased numbers of U-boats being produced would be able to find convoys with the advantage of intelligence gained through B-Dienst decryption of British Naval Cypher Number 3.[7] Only 20 percent of the 180 trans-Atlantic convoys, from the end of July 1942 until the end of April 1943, lost ships to U-boat attack.[8]

On 6 March U-405 sighted the convoy,[5] which had been scattered by nine consecutive days of northwesterly Force 10 gales and snow squalls.[9] The storm damaged the radio communication system aboard the escort commander's ship Spencer and Dauphin had to leave the convoy with damaged steering gear.[6] U-230 torpedoed the British freighter Egyptian on the night of 6–7 March.[10] The British freighter Empire Impala stopped to rescue survivors and was torpedoed after dawn by U-591.[10]

U-190 torpedoed the British freighter Empire Lakeland when the gale subsided on 8 March and four more stragglers were sunk by U-526, U-527, U-591, and U-642.[5] On 9 March the convoy escort was reinforced by No. 120 Squadron RAF B-24 Liberators from Northern Ireland and by the Wickes-class destroyer USS Babbitt and the Treasury-class cutters USCGC Bibb and USCGC Ingham from Iceland.[5]

U-530 torpedoed straggling Swedish freighter Milos on the evening of 9 March. That night U-405 torpedoed the Norwegian freighter Bonneville while U-229 torpedoed the British freighter Nailsea Court and U-409 torpedoed the British escort oiler Rosewood and American ammunition ship Malantic.[11]

The Flower-class corvettes HMS Campion and Mallow reinforced the convoy escort on 10 March,[5] and the convoy reached Liverpool on 14 March.[10] Only 76 of the 275 crewmen of the sunken ships were rescued.[6]

• Convoy Battles of World War II

• Hague, Arnold (2000). The Allied Convoy System 1939–1945. Naval Institute Press. ISBN 1-55750-019-3.
• Milner, Marc (1985). North Atlantic Run. Naval Institute Press. ISBN 0-87021-450-0.
• Morison, Samuel Eliot (1975). History of United States Naval Operations in World War II, Volume I The Battle of the Atlantic 1939–1943. Little, Brown and Company.
• Rohwer, J; Hummelchen, G (1992). Chronology of the War at Sea 1939–1945. Naval Institute Press. ISBN 1-55750-105-X.
• Tarrant, VE (1989). The U-Boat Offensive 1914–1945. Arms and Armour. ISBN 1-85409-520-X.