'Reissewolf' was a U-boat wolfpack operation in the North Atlantic against the HG.75 convoy (22/31 October 1941).

The wolfpack comprised U-73, U-77, U-101, U-432, U-502, U-568 and U-751, and for the loss of none of its own number sank one 1,574-ton ship.

At the end of the attack on the SC.48 convoy on 22 October, U-73, U-77, U-101, U-432, U-502, U-568 and U-751 formed the new 'Reissewolf' wolfpack in the central part of the North Atlantic, while U-38, U-82, U-84, U-85, U-93, U-123, U-202, U-203 and U-569, just arriving from bases in German-occupied France, were instructed on 28 October to establish the 'Schlagetot' wolfpack to the north-west of the 'Reissewolf' wolfpack’s patrol line.

On 20 October, while still in transit, U-84 spotted and reported its sighting of parts of the SL.89 convoy, and on 21 October made an unsuccessful attack. Kapitänleutnant Karl-Heinz Moehle’s U-123 came up and torpedoed the 13,984-ton British armed merchant cruiser Aurania, which suffered severe damage. In the evening U-123 then directed U-203 and Oberleutnant Siegfried Rollman’s U-82 to the convoy, and the latter sank two British ships in the form of the 4,099-ton Serbino and 5,281-ton Treverbyn.

On 22 October the convoy, which was being escorted by the sloops Wellington and Stork, destroyer Beverley, and corvettes Asphodel and Clematis, was located by German air reconnaissance, but U-85, U-202 and U-203 were driven off on 23 October before they could implement any attack, and the wolfpack was ordered to its new line once again. U-123 was instructed to operate in the Belle Isle Strait.

Meanwhile the British, working on the basis of 'Ultra' intelligence derived from German radio traffic intercepted since 21 October, came to the conclusion that at least 10 U-boats were near the 'Reissewolf' wolfpack’s patrol line and accordingly ordered nearby convoys to make wide detours. The most important of these convoys was the HX.155 convoy of 59 ships supported by Commander J. N. Opie’s US Task Unit 4.1.7 (destroyers Roe, Bainbridge, Sturtevant, Overton and Truxtun), which was to be relieved at the Mid-Ocean Meeting Point on 25 October by Commander D. G. F. W. MacIntyre’s British 5^th Escort Group (destroyers Vanoc and Volunteer, corvettes Gentian, Hibiscus, Honeysuckle, Hyacinth, Myosotis, Periwinkle and Sweetbriar, and two anti-submarine trawlers) arriving from the support of the ONS.27 convoy of 62 ships after being replaced by Lieutenant Commander J. C. Hibbard’s Canadian Escort Group 4.1.15 (destroyers Skeena and Columbia, and corvettes Brandon, Camrose, Shediac, Wetaskiwin and Free French Mimose).

Other convoys which were re-routed were the C.4 fast troop convoy and the SC.50 convoy of 36 ships supported by Lieutenant Commander H. Kingsley’s Canadian Escort Group 4.1.13 (St Croix and Restigouche, and corvettes Alberni, Bittersweet, Collingwood, Mayflower and Free French Alysse), which was to be relieved at the Mid-Ocean Meeting Point on 28 October by Commander H. W. Falcon-Steward’s British 1^st Escort Group (destroyers Venomous, Sabre and Rockingham, corvette Alisma, five anti-submarine trawlers, and one rescue ship) arriving with the ON.28 convoy of 40 ships.

On 25 October the SC.50 convoy passed just to the south of the 'Reissewolf' wolfpack’s patrol line, and the ON.26 convoy of 32 ships, supported by the US Task Unit 4.1.5 (destroyers Mayo, Schenk, Leary, Broome and Babbitt, later supplemented by Badger and Greer), passed between the still-forming 'Schlagetot' wolfpack and the four boats of the 'Mordbrenner' wolfpack off the Belle Isle Strait.

The ONS.27 convoy was directed to the north along the route just taken by the ON.26 convoy. On 25 October the support of the ON.28 convoy was assumed at the Mid-Ocean Meeting Point by the US TU4.1.6 (destroyers Sampson, Bernadou, Dupont, Lea and MacLeish, accompanied by the oiler Salinas) coming from Iceland, and the ON.28 convoy was routed to the south.

On 29 October the destroyers depth-charged a suspected U-boat, which was in fact a false echo. The Mid-Ocean Meeting Point for the SC.50 convoy and the 1^st Escort Group was then postponed to 31 October and shifted farther to the south. On 27 October the outbound U-74 sighted and reported the ON.28 convoy, and the 'Reissewolf' wolfpack was now ordered to intercept this. Also outbound, Kapitänleutnant Jürgen Oesten’s U-106 sank the 5,120-ton British King Malcolm of the SC.50 convoy. On 28, 29 and 30 October, U-568, U-77, U-73, U-751 and U-106 successively maintained contact, but were several times driven off by the attacks of the five US destroyers and, with the exception of U-77 and U-74 on single occasions, could not gain a firing position. U-568, U-751, U-77 and U-502 were now compelled by their fuel situation to break off, and joined the 'Stosstrupp' wolfpack. Thus only only U-73, U-74 and U-106 were able to continue the shadowing task. On 31 October Oesten’s U-106 torpedoed the 8,026-ton US Navy oiler Salinas, but was unable to close and finish the ship because of the counterattacks of Dupont and Lea, later supported by the US Coast Guard cutter Campbell and US Navy tug Cherokee.

The boats of the 'Mordbrenner' pack, directed to the scene, were unable to approach the convoy, whose escort was strengthened by the arrival of the US destroyers Leary, Babbitt and Schenck, from St John’s after leaving the ON.26 convoy, and Buck and Ludlow, waiting for the next 'HX' convoy. The fruitless search was broken off on 1 November after U-74 had maintained contact for more than 1,850 miles (2975 km).

On 24/25 October, at the Western Ocean Meeting Point, the support of the HX.156 convoy of 44 ships and the SC.51 convoy of 37 ships was taken over by Commander Webb’s US TU4.1.3 (destroyers Benson, Hilary P. Jones, Niblack, Reuben James and Tarbell) and Canadian Escort Group 4.1.11 (destroyer St Laurent, and corvettes Arrowhead, Chilliwack, Snowberry, Trail and British Nasturtium, Polyanthus and Primrose).

On 25/26 October 'Ultra' intelligence suggested that there were four U-boats off the Belle Isle Strait and up to 20 in the central part of the North Atlantic, so both convoys were re-routed to the south of the U-boat areas. On 25 and 29 October Hilary P. Jones depth-charged suspected (but false) U-boat contacts, and on 27 October was damaged in heavy seas.

On 27 October, the 'Reissewolf' wolfpack made contact with the ON.28 convoy, and the HX.156 and SC.51 convoys were detoured farther to the south. The boats of the 'Reissewolf' wolfpack scored no hits on the ON.29 convoy, but Oberleutnant Heinz-Otto Schultze’s U-432 sank the 1,574-ton British Ulea, of the HG.75 convoy, on 28 October.