'Kanal' was the German U-boat response in the English Channel against the ships of the Allied 'Neptune' (iii) naval forces delivering and supporting the land forces for 'Overlord' (6/30 June 1944).
The Allies were more concerned by the possibility of U-boat attacks on their invasion forces than by the possibility of air attack on them, and therefore deployed very significant air and surface ship strength to guard against this possibility.
The forces readied for use against any emerging U-boat threat to 'Neptune' (iii) and 'Overlord' comprised the anti-submarine squadrons of Air Vice Marshal B. E. Baker’s reinforced No. 19 Group within Air Marshal Sir William Sholto Douglas’s RAF Coastal Command and, under the command of Admiral Sir Max Horton, heading the Western Approaches command, the escort carriers Vindex, Tracker and Activity together with three destroyer and seven frigate escort groups steaming overlapping patrol areas and schedules to close the western end of the English Channel to the possible ingress of U-boats from the bases on the west coast of German-occupied France or curtailing their operations in the Atlantic.
These escort groups were the 14th Escort Group with the British destroyers Fame, Havelock, Hotspur, Icarus and Inconstant; the 11th Escort Group with the Canadian destroyers Chaudiere, Gatineau, Kootenay, Ottawa and St Laurent; the 12th Escort Group with the Canadian destroyers Qu’Appelle, Restigouche, Saskatchewan and Skeena; the 9th Escort Group with the Canadian frigates Matane, Meon, Port Colborne, St John, Stormont and Swansea; the 1st Escort Group with the British frigates Affleck, Balfour, Bentley, Capel, Garlies and Gore; the 6th Escort Group with the Canadian frigates Cape Breton, Grou, Outremont, Teme and Waskesiu; the 3rd Escort Group with the British frigates Blackwood, Cooke, Domett, Braithwaite, Duckworth and Essington; the 5th Escort Group with the British frigates Aylmer, Bickerton, Bligh, Goodson and Keats; the 15th Escort Group with the British frigates Inglis, Lawson, Louis, Moorsom and Mounsey and attached Cam; and the 2nd Escort Group with the British sloops Starling, Woodpecker and Wren and the frigates Loch Killin, Loch Fada and Dominica.
From 6 June four to six of the frigate groups operated in the area to the west of the English Channel and in the Bay of Biscay, and two of the destroyer groups in the western entrance to the English Channel.
On 6 June a total of 17 U-boats departed Brest, 14 St Nazaire, four La Pallice and one Lorient from the 'Landwirt' pack. On 7 June Oberleutnant Hans-Heinrich Baden’s homebound U-955 was sunk in the Bay of Biscay by a Short Sunderland of No. 201 Squadron RAF. On 8 June, of the outbound Brest boats, Kapitänleutnant Hans-Heinrich Ketels’s U-970 was sunk by a Sunderland of No. 228 Squadron RAF, while a Vickers Wellington of No. 179 Squadron RAF damaged U-415, a Consolidated Liberator of No. 53 Squadron RAF damaged U-963 and U-256, one of which shot down another Liberator of the same squadron.
On 7 June U-989 was damaged by a Wellington of the RCAF’s No. 407 Squadron and a Liberator of the RAF’s No. 224 Squadron, which were both shot down by the U-boat, however. U-212 was damaged by two de Havilland Mosquito aircraft of the RAF’s No. 248 Squadron. The damaged U-boats had to return to base for repairs.
On 8 June a Liberator of the RAF’s No. 53 Squadron sank Oberleutnant Hans-Helmuth Bugs’s U-629, and a Liberator of the RAF’s No. 224 Squadron sank Oberleutnant Detlef von Hehsten’s U-373 and possibly Kapitänleutnant Klaus Hartmann’s U-441, while a Handley Page Halifax of the RAF’s No. 502 Squadron damaged U-413. Kapitänleutnant Günther Stark’s U-740 was lost on or after 6 June to unknown causes.
It proved impossible for any U-boat not fitted with a Schnorchel breathing mast to enter the English Channel, and accordingly U-766 of the Brest-based boats, U-228, U-255, U-260, U-270, U-281, U-382, U-437, U-445, U-608, U-650, U-714, U-758, U-985 and U-993 of the St Nazaire-based boats, U-262 and U-333 of the La Pallice-based boats, and U-981 from Lorient remained on station in the Bay of Biscay until 15 June.
Of the nine boats fitted with Schnorchel masts, U-212 had to return twice while the other eight sought to reach the waters off the invasion beaches, followed by U-767, U-1191, U-988, U-671 and U971 arriving from bases in German-occupied Norway.
On 7 and 8 June U-984, U-621 and U-953 fired four, two and four T5 acoustic-homing torpedoes at the four destroyers of the 12th Support Group, but all the torpedoes detonated prematurely or in the ships' wakes, and on 9 June U-764 fires four T5 torpedoes at a destroyer but did not score a hit.
Up to 11 June, U-621, U-269 and U-275 made unsuccessful attacks on groups of destroyers in the western end of the English Channel. Oberleutnant Ulrich Knackfuss’s U-821 was sunk in an attack by four Mosquito warplanes of the RAF’s No. 248 Squadron, of which one was lost, and a Liberator of the RAF’s No. 206 Squadron. On 11 June a Sunderland of the RAF’s No. 228 Squadron damaged U-333 but was itself shot down. On 12 June a Liberator of the RAF’s No. 224 Squadron was shot down, and on 13 June U-270 shot down a Liberator of the RAF’s No. 53 Squadron but was itself damaged by a Wellington of the RAF’s No. 172 Squadron.
It was only on 14 June that the first U-boats managed to reach the cross-channel shipping routes, and at the same time so too did some of the Allied support groups. On this day U-984 missed a hunting group, and on 15 June Oberleutnant Hermann Stuckmann’s U-621 sank the tank landing ship LST-280, Oberleutnant Walter Dankleff’s U-767 sank the frigate Mourne of the 5th Support Group, and Oberleutnant Hanskurt von Bremen’s U-764 ravaged the frigate Blackwood of the 4th Support Group: the frigate was taken in tow but later deemed a total loss.
On 18 June U-621 missed two US battleships with a torpedo salvo. On the same day Dankleff’s U-767 was sunk by the destroyers Fame, Inconstant and Havelock of the 14th Support Group.
Of the Schnorchel-fitted boats which arrived in the area during the June, U-763 missed a search group with two T5 torpedoes during the night 22/23 June. After being damaged in attacks by single Wellington aircraft of the RCAF’s No. 407 Squadron and RAF’s No. 502 Squadron on 20 June, and by a Liberator of No. 311 (Czech) Squadron on 26 June, Oberleutnant Walter Zeplien’s U-971 was sunk in the western part of the English Channel by the destroyers Eskimo and Haida after the boast’s attempt to attack had been foiled by a torpedo firing fault. On 25 June the frigate Bickerton sank Oberleutnant Georg Uhl’s U-269. The frigates Affleck and Balfour, reported the sinking of U-1191 (lost to unknown causes on on after 12 June), but more probably hit the wreck of U-629. U-984 of the same group torpedoed Goodson but missed a frigate. Oberleutnant Klaus-Dietrich Steffens’s Schnorchel-fitted U-719 was sunk on 26 June by the destroyer Bulldog.
Between 27 and 29 June, Oberleutnant Erich Dobberstein’s U-988 torpedoed the corvette Pink, which was declared a total loss, and sank two British merchant ships (2,385-ton Maid of Orleans and 7,058-ton Empire Portia) before itself being sunk on 29 June by a Liberator the RAF’s No. 224 Squadron and the frigates Essington, Duckworth, Domett and Cooke of the 3rd Support Group.
On 29 June Oberleutnant Heinz Sieder’s U-984 attacked the EMC.17 convoy and hit four US ships, namely the 7,176-ton H. G. Blasdel, 7,240-ton Edward M. House, 7,198-ton John A. Treutlen and 7,176-ton James A. Farrell: the second of these was saved by being run aground and was later salvaged, but the other three sank.
U-671 missed a destroyer of a search group on 30 June and, after another unsuccessful attack on a search group on 2 July, the boat was damaged by depth charges and had to put in to Boulogne. The Schnorchel-equipped U-214 and U-218 laid mines off Plymouth on 26 June and off Land’s End on 1 July, and a 7,177-ton vessel was damaged on 6 July on the latter.
By 30 June 570 Liberty ships, 788 coastal motor boats, 905 tank landing ships, 1,442 tank landing craft, 180 troop transports and 372 infantry landing craft had reached the invasion area in supply convoys escorted chiefly by British and Canadian corvettes.