This was a U-boat wolfpack operation in the Atlantic against the SC.153, SL.150, MKS.41, CU.16, SC.154, HX.281 and ON.227 convoys (22 February/22 March 1944).
Established in an area to the west of Ireland, the wolfpack comprised U-91, U-92, U-212, U-255, U-256, U-262, U-267, U-281, U-302, U-311, U-358, U-415, U-437, U-441, U-448, U-549, U-575, U-603, U-608, U-625, U-653, U-667, U-672, U-709, U-741, U-744, U-764, U-962, U-963, U-985 and U-986. For the loss of Kapitänleutnant Heinz Hungershausen’s U-91, Kapitänleutnant Rolf Manke’s U-358, Oberleutnant Wolfgang Boehmer’s U-575, Kapitänleutnant Hans-Joachim Bertelsmann’s U-603, Oberleutnant Siegfried Straub’s U-625, Oberleutnant Hans-Albrecht Kandler’s U-653, Oberleutnant Rudolf Ites’s U-709 and Oberleutnant Heinz Blischke’s U-764, the wolfpack sank five ships (15,374 tons including the British frigate Gould, British tank landing ship LST-362, US destroyer escort Leopold and British corvette Asphodel), and damaged the 1,625-ton British LST-324.
Constituting a major defeat for the U-boat arm, this was the final wolfpack operation in the North Atlantic with U-boats carrying only conventional rather than a mix of conventional and homing torpedoes. On establishment, the ‘Preussen’ wolfpack had U-333, U413 and U-621 on patrol to the south of Ireland, in the North Channel and in the North Minch, U-546 off Iceland and U-549, U-552 and U-550 operating individually as meteorological reconnaissance boats.
On 24 February the inbound U-257 encountered the escort of the SC.153 convoy, namely Commander H. F. Pullen’s Canadian Escort Group C5 centred on the destroyer Ottawa, the Canadian 3rd Escort Group (frigates Duckworth, Berry, Cooke, Dornett, Essington and Rowley) and the Canadian 6th Escort Group (frigates Cape Breton, Grou, Nene, Outremont and Waskesiu), and was sunk by Waskesiu and Nene. U-989 attempted unsuccessfully to reach a group of the convoy’s stragglers.
As a result of 'Ultra' intelligence derived from decrypts of the U-boats' signals, the HX.279 convoy was re-routed clear of the ‘Preussen’ wolfpack, and so too was the ON.225 convoy during 26 February. To the west of Ireland, support for the convoy was provided by Commander C. Gwinner’s British 1st Support Group with the frigates Affleck, Gore, Gould, Garlies, Balfour and Capel. The first three of these frigates sank U-91 on 25 February but, after a 38-hour search, U-358 sank Gould on 29 February while Gore and Garlies were not present. Affleck then sank U-358.
The destroyer escorts of Captain Logan C. Ramsey’s US TG21.16 (escort carrier Block Island, destroyer Corry, and destroyer escorts Thomas, Bronstein, Bostwick and Breeman) sank U-709 and U-603 some 700 miles (1125 km) to the north of the Azores islands group on 1 March.
To the west of the Bay of Biscay, U-744 sank the 4,080-ton British LST-362 on 2 March. However, on 5 March the boat was found by the escort of the HX.280 convoy, namely Commander P. W. Burnett’s Canadian Escort Group C2 (destroyers Gatineau, Chaudière and British Icarus, frigate St Catherines, and corvettes Chilliwack and Fennel) after a 30-hour search with support from the British corvette Kenilworth Castle. After firing several torpedoes at its attackers, U-744 was sunk.
Over the following days U-267, U-625, U-653, U-672, U-741 and U-986 and the Schnorchel-fitted U-415 and U-575 joined the ‘Preussen’ wolfpack. U-575 sank the corvette Asphodel from the escort of the SL.150/MKS.41 convoys on 9 March, her survivors being rescued by the corvette Clover. On the same day U-255 was located near the CU.16 convoy, which was supported by Captain Kenner’s US TG21.5 (destroyer escorts Joyce, Poole, Harveson, Kirkpatrick, Leopold and Peterson) by Leopold, but was able to sink the approaching destroyer escort and only narrowly missed Joyce.
On 10 March U-845 sighted and reported the SC.154 convoy, supported by the Canadian Escort Group C1, and after a long evasion was sunk by the Canadian destroyer St Laurent, British destroyer Forester, Canadian frigate Swansea and Canadian corvette Owen Sound. Torpedo attacks by U-653 and U-575 failed.
The HX.281 convoy, supported by Commander R. A. Currie’s British Escort Group B6 (destroyer Fame, frigates Deveron and Antigua, and corvettes Kingcup, Vervain, Eglantine, Rose and Acanthus) passed through the U-boat patrol lines on 10 March without incident.
U-625 was sunk on 10 March by a Short Sunderland flying boat of the RCAF’s No. 422 Squadron, which was escorting the SC.154 convoy. U-741 and U-256 were instructed to assist, and shot down a Vickers Wellington medium-range anti-submarine aeroplane of the RCAF’s No. 407 Squadron.
The ON.227 convoy, which turned away south to avoid the U-boat patrol lines, was escorted on 12 and 13 March by strong air formations from Cornwall and the Azores islands group. But U-311 shot down a Boeing Fortress long-range patrol bomber of the RAF’s No. 206 Squadron. U-575 was attacked by a Wellington of the RAF’s No. 172 Squadron and two Fortress aircraft of the RAF’s Nos 206 and 220 Squadrons, and hunted by Captain Joseph B. Dunn’s US TG21.11 (escort carrier Bogue with the Grumman Avenger bombers of the VC-95 squadron, destroyer Hobson, destroyer escorts Haverfield, Janssen, Willis and Swenning, and Canadian frigate Prince Rupert) of the escort group. The U-boat was sunk after shooting down one Avenger. On 14 March the sloops Starling and Wild Goose of Captain F. J. Walker’s British 2nd Support Group, with the help of a Fairey Swordfish anti-submarine aeroplane of the Fleet Air Arm’s No. 825 Squadron from the escort carrier Vindex, sank U-653.
On 17 March U-415 was damaged by escorts of the CU.17 convoy, from which U-311 sank the 10,342-ton US tanker Seakay on 19 March.
By this time it had become all too clear to the Germans that the standard pattern of their convoy operations were no longer practical in the North Atlantic using conventional boats and straight-running T5 torpedoes, so Grossadmiral Karl Dönitz, commander-in-chief of the German navy but still exercising day-to-day control of the U-boat arm via Konteradmiral Eberhard Godt, the service’s operations chief, ordered the break-up of the ‘Preussen’ wolfpack, whose surviving U-92, U-255, U-262, U-267, U-302, U-311, U-437, U-667, U-672, U-741, U-962 and U-986 then continued individual operations.