This was a U-boat wolfpack operation, in tandem with ‘Specht’, in the Atlantic against the ONS.5 convoy (27 April/4 May 1943).
The wolfpack comprised U-192, U-209, U-231, U-258, U-378, U-381, U-386, U-413, U-528, U-531, U-532, U-533, U-552, U-648, U-650 and U-954, and for the loss of none of its own number sank one 6,198-ton ship of the ONS.5 convoy.
While the boats of the ‘Specht’ wolfpack were ordered to move to the north-west for the interception of the ON.179 and ONS.4 convoys, as a result of ‘Ultra’ intelligence these convoys were both re-routed into the area to the north of the wolfpack, to be covered respectively by the 5th and 1st Escort Groups (sloops Pelican and Sennen, and frigates Jed, Spey and Wear) detached from support of the SC.127 convoy, which now became the target of the new ‘Amsel’ group of wolfpacks.
Supported by the Commander E. C. L. Day’s British Escort Group B4 (destroyers Highlander, Beverley and Vimy, and corvettes Abelia, Anemone, Asphodel, Clover, Pennywort and Canadian Rosthern), which had been relocated from the HX.234 convoy, the SC.127 convoy passed to the north, however, and also edged round the new ‘Star’ wolfpack. On its way to join the rest of the ‘Star’ wolfpack, Oberleutnant Hans-Abrecht Kandler’s U-386 sank the 1,997-ton British Rosenborg of the RU.71 convoy on 24 April.
On 28 April the ‘Star’ wolfpack formed a patrol line in the area to the south of Iceland for the interception of the ONS.5 convoy of 42 ships supported by Commander P. W. Gretton’s British Escort Group B7 (destroyers Duncan and Vidette, frigate Tay, corvettes Loosestrife, Pink, Snowflake and Sunflower, and anti-submarine trawlers Northern Gem and Northern Spray).
The convoy was spotted and reported by U-650 which, despite being forced to dive several times by the presence of Consolidated Catalina flying boats of the US Navy’s VP-84 squadron, brought up U-378 and U-386 by day. During the night of 28/29 April, U-386 was depth-charged and damaged by Sunflower, and U-650 and U-532 were depth-charged after misses on Duncan and Snowflake; U-532 was attacked once again in daylight, this time by Tay, on 29 April. In a daylight submerged attack, Kapitänleutnant Wilhelm von Mässenhausen’s U-258 sank the 6,198-ton US McKeesport. U-528 was damaged by a Catalina of the VP-84 squadron.
At this stage Admiral Sir Max Horton, heading the Western Approaches Command, sent the destroyer Oribi from the SC.127 convoy’s escort, as well as Captain J. A. McCoy’s 3rd Support Group (destroyers Offa, Impulsive, Panther and Penn) from St John’s, Newfoundland, to add further capability to the defence of the ONS.5 convoy.
On 30 April and during the night of 30 April/1 May the weather became worse, and in conditions of changing visibility and radio interference, the ‘Star’ wolfpack lost contact with the convoy after U-192 had made an unsuccessful night attack on 1 May. By first light on the following day the convoy had been compelled to heave-to in a strong gale, and some of the ships become separated from the convoy.
After the B-Dienst radio intercept and decryption service’s 29 April location of the SC.128 convoy of 33 ships supported by the 40th Escort Group (sloops Landguard, Lulworth and Hastings, frigates Moyola and Waveney, corvettes Poppy and Starwort, and anti-submarine trawler Northern Gift), the ‘Specht’ and ‘Amsel’ wolfpacks were disposed in a semi-circle along the convoy’s course. During the evening of 1 May U-628 sighted and reported the convoy’s smoke, but the boats ordered to the location were diverted by flares, fired by the escorts on the flank, and the SC.128 convoy avoided the boats by getting west of them.
The boats of the ‘Star’ and ‘Specht’ wolfpacks coming from the attack on the ONS.5 convoy were concentrated in a new patrol line ahead of the SC.128 convoy for 4 May. The new patrol line was formed by U-125, U-168, U-192, U-209, U-226, U-231, U-260, U-264, U-270, U-358, U-378, U-381, U-413, U-438, U-514, U-531, U-533, U-552, U-584, U-614, U-628, U-630, U-648, U-650, U-662, U-707 and U-732.
The convoy passed to the west, however, and during this period a Canadian Boeing Canso flying boat of the RCAF’s No. 5 Squadron damaged Kapitänleutnant Heinrich Brodda’s U-209, which was lost on 8 May, possibly as a result of the damage sustained in this air attack. In the evening ONS.5, approaching from the north, arrived in the middle of the ‘Fink’ wolfpack and was reported by U-628. The ‘Fink’ wolfpack and those located farther to the south (‘Amsel I’, ‘Amsel II’ and two returning boats) were immediately deployed against this target.
As refuelling at sea was made impossible on 2, 3 and 4 May by the heavy seas, Gretton was forced to take Duncan, Impulsive, Penn and Panther, all very short of fuel, away from the convoy. On 4 May Lieutenant Commander R. E. Sherwood, commanding the escort force (frigate Tay, destroyers Offa, Oribi and Vidette, and corvettes Loosestrife, Snowflake and Sunflower) were still with the convoy of 31 ships. Pink was astern with six stragglers, and another five stragglers and Northern Spray were attempting to catch up with the convoy’s main body. Kapitänleutnant Ulrich Folkers’s U-125 sank one of them, the 4,737-ton British Lorient, during the afternoon. On 4 May five boats arrived by day and another six by night, and the wolfpack established firm contact with the convoy. Some of the boats were driven off by Tay, Offa and Oribi, and U-270 was depth-charged and damaged by Snowflake and Oribi. Of the attacking boats, Kapitänleutnant Heinrich Hasenschar’s U-628 sank the 5,081-ton British Harbury, Kapitänleutnant Hartwig Looks’s U-264 the 4,568-ton British Harperley and 5,561-ton US West Maximus, and Kapitänleutnant Rolf Manke’s U-358 the 2,864-ton British Bristol City and 5,212-ton British Wentworth.
By day on 5 May U-192 encountered the straggler group escorted by Pink, which then located and attacked U-358 with her ‘Hedgehog’ projector, though the boat escaped. A short time after this, Oberleutnant Günter Gretschel’s U-707 sank the 4,635-ton British North Britain of this group.
During the course of the day, some 15 boats established contact with the ONS.5 convoy and in submerged attacks Kapitänleutnant Joachim Deecke’s U-584 sank the 5,565-ton US West Madaket and Kapitänleutnant Ralf von Jessen’s U-266 the 1,570-ton Norwegian Bonde, 5,306-ton British Gharinda and 5,136-ton British Selvistan.
Just as dusk started to set in there appeared a mist that persuaded the U-boat captains to make a rapid approach toward the escorts, which were thus able to locate the boats on radar. Sunflower’s radar detected four boats in quick succession and the corvette then damaged U-267 with gunfire after the boat had missed with a torpedo. Loosestrife detected two boats, surprised Oberleutnant Werner Happe’s U-192 during an attempted attack, and depth-charged and sank it. Vidette drove off three boats. Almost simultaneously Snowflake detected three boats, of which U-531 missed the corvette before being depth-charged and forced to the surface. Of the warships ordered to provide support, Oribi encountered and rammed Folkers’s U-125: the boat initially got away in a squall, but was then found by Snowflake which, with her depth charges all expended, sank the boat with gunfire. Sunflower located and rammed U-533, which escaped despite being badly damaged. Vidette detected Kapitänleutnant Herbert Neckel’s U-531, which had submerged again, and sank it with her ‘Hedgehog’ projector. Offa tried to ram a U-boat in the process of diving and therefore failed, and Loosestrife made three more depth-charge attacks.
Toward morning Commander G. N. Brewer’s 1st Escort Group (sloops Pelican and Sennen, and frigates Jed, Spey and Wear) arrived on the scene after being despatched from St John’s. Pelican spotted Kovettenkapitän Heinrich Heinsohn’s U-438 on radar and, in concert with Jed, sank it. On her way to the straggler group escorted by Pink, Jed encountered U-575 and U-650, slightly damaging the former with gunfire before the two boats managed to make their escape. On 6 May Vidette depth-charged and sank Oberleutnant Werner Winkler’s U-630.
During the morning of this day Grossadmiral Karl Dönitz, still in day-to-day command of the U-boat arm via Konteradmiral Eberhard Godt, the Chef der Operationsabteilung des Befehlshaber der Unterseeboote, despite being commander-in-chief of the German navy in January 1943, terminated the operation.