'Stosstrupp' was a U-boat wolfpack operation in the Atlantic against the HX.156 convoy (30 October/4 November 1941).
The wolfpack comprised U-96, U-133, U-552, U-567, U-571 and U-577, and for the loss of none of its own number sank one 5,998-ton ship of the OS.10 convoy and also the US destroyer Reuben James, which was part of the escort for the HX.156 convoy.
On 30 October, fresh outbound boats were ordered to concentrate as the 'Stosstrupp' wolfpack in the area to the east of the Newfoundland Bank with U-96, U-133, U-552, U-571, U-567 and U-577, which were supplemented by U-77, U-502, U-568 and U-751 detached from the 'Schlagetot' wolfpack as a result of their fuel situation.
During the morning of 31 October, as the wolfpack was moving toward its designated operational area, Kapitšnleutnant Erich Topp’s U-552 sighted and reported the HX.156 convoy of 44 ships (including three fighter-equipped CAM-ships) supported by Commander Richard E. Webb’s US Task Unit 4.1.3 (destroyers Benson, Hilary P. Jones, Niblack, Reuben James and Tarbell), immediately attacked and sank Reuben James. U-552 was driven off in the afternoon, but U-567 then reached the area. On 1 November TU4.1.3 was relieved by Commander W. T. Couchman’s British 6th Escort Group (destroyers Broke, Buxton and Wolverine, corvettes Begonia, Camellia, Canadian Moosejaw and Free Norwegian Eglantine and Montbretia, and the anti-submarine trawler King Sol), but U-552 and U-567 maintained contact up to 3 November. Two attacks were attempted on 1 November, but both failed.
Searching for the HX.156 convoy on 31 October, Kapitšnleutnant Heinrich Lehmann-Willenbrock’s U-96 encountered the OS.10 convoy, supported by the British 40th Escort Group (sloops Bideford, Gorleston and Lulworth, and corvettes Gardenia and Free French Commandant Duboc), attacked and sank the 5,998-ton Dutch Bennecom. The returning and outbound U-77, U-502, U-568, U-571 and Italian Barbarigo were ordered to intercept and, because U-96 was still in contact, U-66, U-98, U-103, U-107, U-201, U-373 and U-572 were also ordered to intervene. German air reconnaissance again sighted and reported the convoy on 2 November, and while U-98 managed to re-establish contact, this was soon lost.