Convoy SL 125

German cryptographers decoded message traffic containing tactical information about convoy SL 125, and wolf pack Streitaxt (battle axe),[3] consisting of U-103, U-134, U-203, U-409, U-440, U-509, U-510, U-572, U-604, and U-659[4] was assembled 23 October to intercept the convoy west of the Canary Islands.[3] The only United States merchant ship and escorting sloop HMS Bridgewater, Isles-class trawler HMS Copinsay and Free French corvette Commandant Drogou had been detached by the time U-203 found the convoy on 25 October.[2] U-203 was depth charged and damaged while attempting to attack the straggling British tanker Anglo Maersk.[3] The tanker was subsequently shadowed by U-134 and damaged by U-509.[3]

The armed merchant cruiser and troopship HMS Esperance Bay was detached with the Shakespearian-class trawler HMS Juliet, tugboat HMS Salvonia, and repair ship HMNZS Kelantan[2] when U-409 found and reported the main convoy of 37 ships on 27 October.[4] Forty-one merchant ships[5] were left in the care of Flower-class corvettes Petunia,[4] Cowslip, Crocus, HMS Dahlia, and Woodruff.[3][6] U-659 was depth charged and damaged while attempting to attack the convoy. After moonrise, U-604 sank the damaged Anglo Maersk[3] while U-509 torpedoed the British freighters Pacific Star and Stentor.[4]

After unsuccessful submerged daylight attacks on 28 October, U-509 sank the British freighter Nagpore and damaged the British freighter Hopecastle after sunset. U-203 sank the damaged Hopecastle before dawn.[7]

U-509 sank the British freighter Britanny during foul weather on the night of 29–30 October.[7] The British tanker Bullmouth (sailing in ballast) was damaged by U-409 and sunk by U-659.[7] The British freighter Corinaldo was damaged by both U-509 and U-659 before being sunk by U-203.[7]

Improved weather brought coordinated attacks on the night of 30–31 October. U-409 torpedoed the British freighter Silverwillow while U-604 torpedoed the British transport President Doumer and the British freighter Baron Vernon.[7] The British freighter Tasmania was damaged by U-659 and sunk by U-103.[7] The Norwegian freighter Alaska was damaged by U-510, but reached England safely with the help of newly arriving escorts.[7]

Long-range bombers of RAF Coastal Command arrived over the convoy on 31 October.[4] Admiral Dönitz cancelled operations on the morning of 1 November.[3] The convoy was reinforced with eleven more escorts[2] and reached Liverpool on 9 November.[5] It had suffered the greatest loss of any SL convoy,[8] but its timing focused the available U-boats in the area away from the Operation Torch convoys for the allied invasion of North Africa on 8 November 1942.[4] Some historians have suggested that the trade convoy SL 125 was an intentional tactical diversion to keep U-boats away from the loaded troop transports.[9] Eleven of the ships surviving this convoy sailed two months later with convoy ON 154, in which four of them were sunk.[10]

• Convoy Battles of World War II

• Blair, Clay (1998). Hitler's U-Boat War The Hunted 1942–1945. Random House. ISBN 0-679-45742-9.
• Edwards, Bernard (1999). Dönitz and the Wolf Packs. Brockhampton Press. ISBN 1-86019-927-5.
• Hague, Arnold (2000). The Allied Convoy System 1939–1945. Naval Institute Press. ISBN 1-55750-019-3.
• Rohwer, J.; Hummelchen, G. (1992). Chronology of the War at Sea 1939–1945. Naval Institute Press. ISBN 1-55750-105-X.