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 effectively search for convoys with the advantage of intelligence gained through B-Dienst decryption of British Naval Cypher Number 3.[5] However, only 20 percent of the 180 trans-Atlantic convoys sailing from the end of July 1942 until the end of April 1943 lost ships to U-boat attack.[6]
26 October
U-436 reported the convoy and shadowed it without being detected by the convoy escort.[7]
27 October
U-436 launched five torpedoes at 2110Z hitting Sourabaya, Gurney Newlin and Frontenac. Alberni and Summerside dropped back to rescue survivors from the torpedoed ships.[4]
28 October
U-606 torpedoed Kosmos II on the starboard side at 0345Z. Barrwhin dropped back to rescue survivors, and both ships were sunk while the convoy proceeded ahead. A patrolling Consolidated B-24 Liberator from No. 120 Squadron RAF in Iceland prevented five U-boats from reaching attack positions during daylight hours but Bic Island and Pan-New York were torpedoed after sunset.[4]
29 October
Northern routing enabled the convoy to pass through the narrowest portion of the air gap, and continuous daylight air patrols forced the U-boats to lose contact with the convoy.[4] The Naval trawlersBodo and Molde escorted the convoy through the Western Approaches on 1 November; and the convoy reached Liverpool on 2 November.[8]
Hague, Arnold (2000). The Allied Convoy System 1939–1945. Naval Institute Press. ISBN1-55750-019-3.
Milner, Marc (1985). North Atlantic Run. Naval Institute Press. ISBN0-87021-450-0.
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. ISBN1-55750-105-X.
Tarrant, V.E. (1989). The U-Boat Offensive 1914–1945. Arms and Armour. ISBN1-85409-520-X.
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