'Jahn' was a U-boat wolfpack operation in the Atlantic (30 October/2 November 1943).
The wolfpack comprised U-226, U-373, U-426, U-437, U-552, U-575, U-586, U-592, U-608, U-648, U-709 and U-842, and neither lost any of its own number nor sank any ship.
From 24 October the 'Siegfried' (v) wolfpack 1 was in position to intercept the expected HX.262 convoy of 63 laden ships eastward-bound from New York to Liverpool supported by Commander H. F. Pullen’s Canadian Escort Group C5 (destroyers Ottawa and British Burnham, and corvettes Arvida, Dauphin and Wetaskiwin) supplemented, after finishing its work in support of the ON.207 convoy, Captain F. J. Walker’s 2nd Support Group (sloops Starling, Kite, Woodcock, Wild Goose and Magpie, and escort carrier Tracker).
Kapitänleutnant Gustav Poel’s U-413 managed to fix the general position of the convoy through use of intermediate-wavelength D/F to listen to the escorts, but the wolfpack’s boats did not arrive sufficiently rapidly to make a 25/26 October interception of the convoy, which passed to the south of the German patrol line. U-608 and U-212 were bombed, a Consolidated Liberator long-range patrol bomber of the RCAF’s No. 10 Squadron damaged U-91, and Oberleutnant Hans-Jürgen Reese’s U-420 disappeared without trace on or some time shortly after 20 October.
The 'Siegfried' (v) wolfpack was then divided into three sections 2, and from 28 October these three 'Siegfried' subcomponents assumed shorter patrol lines east of Newfoundland in the expectation of intercepting the SC.145 convoy of 32 ships bound from Halifax. Nova Scotia, to Liverpool and supported by Commander R. A. Currie’s British Escort Group B6 (destroyers Fame and Vanquisher, frigate Deveron, and Free Norwegian corvettes Eglantine, Potentilla and Rose) aided by Captain E. W. Anstice’s 8th Support Group (escort carrier Fencer, and destroyers Inconstant and Free Polish Garland and Burza).
Located at one end of the German patrol lines, Kapitänleutnant Hans-Joachim Schwebcke’s U-714 sent several misleading radio messages deliberately intended for interception by the Allies and achieved its purpose by persuading the British to reroute the convoy straight into the maximum strength of the patrol lines. On 29 October the anti-aircraft fire of U-405 and U-608 drove off Fairey Swordfish anti-submarine aircraft launched from Fencer, but the convoy passed unnoticed.
Farther to the east, the approaching U-282 was located on radar by Vidette, which with Lieutenant Commander R. Hart’s British Escort Group B7 had been ordered to support the ON.208 convoy, itself supported by Commander M. J. Evans’s British Escort Group B3 (frigate Towy, destroyer Keppel and corvettes Narcissus, Orchis and Free French Lobélia, Renoncule and Roselys).
Oberleutnant Rudolf Müller’s U-282 was then sunk by the 'Hedgehog' bombs of the corvette Sunflower.
The British Escort Group B7 was detached from the support of the ON.208 convoy to aid the HX.263 convoy and its support, Lieutenant Commander E. H. Chavasse’s 4th Support Group (frigates Bentinck, Bazely, Blackwood, Burgess, Byard, Drury and Berry).
On 31 October Grossadmiral Karl Dönitz, commander-in-chief of the German navy but still in day-to-day command of the U-boat arm via Konteradmiral Eberhard Gost, the service’s operational commander, ordered a major concentration of force against these convoys and also the ONS.21 convoy supported by Commander P. W. Burnett’s Canadian Escort Group C2 (destroyers Gatineau and British Icarus, and corvettes Drumheller, Fennel and Kamloops). Dönitz formed the 'Körner' wolfpack (U-212, U-231, U-267, U-280, U-281, U-413, U-586, U-714, U-843, U-963 and U-969) and also the 'Jahn' wolfpack in the area to the east of Newfoundland.
However, only U-714 sighted even one aeroplane, on 1 November and then to the extreme north. The convoys in fact passed round the wolfpacks, and when this became apparent the boats were therefore subdivided into the 'Tirpitz I' to 'Tirpitz V' wolfpacks, each of four or five boats, to locate and attack the HX.264 convoy and its Escort Group C1, which were expected from 5 November. The Canadian Escort Group C1 was in fact itself strengthened by Walker’s 2nd Support Group, and aircraft launched from Tracker forced U-967 to dive on 5 November. In the evening Kite sighted Oberleutnant Albrecht Gänge’s U-226, and on the following morning Walker sank the boat with Woodcock and Starling. In the afternoon Wild Goose located Korvettenkapitän Wolfgang Heller’s U-842 and, operating in concert with Starling, sank it. The convoy passed undetected.
On 7 November the Germans had to end the operation as further surfaced operations by day had become prohibitively costly in the face of rampant Allied air superiority. In the course of 8 November the 2nd Escort Group, which was returning to Argentia to refuel, passed the patrol line of the 'Tirpitz V' wolfpack, and Oberleutnant Peter-Arthur Stahl’s U-648 just missed the escort carrier Tracker with a salvo of three torpedoes, and a sloop with one torpedo.