'Stürmer' (ii) was a U-boat wolfpack operation in the Atlantic against the OS.66 and KMS.40 convoys (26 January/3 February 1944).
The wolfpack comprised U-283, U-309, U-386, U-390, U-406, U-545, U-547, U-666, U-731, U-762, U-984, U-985 and U-989, and neither lost any of its own number nor sank any ship.
German air reconnaissance on 20, 21 and 22 January was not able to locate the HX.275, ON.220 and SC.151 convoys, which were expected on the basis of intelligence from the B-Dienst naval signals intercept and analysis service, but on 26 and 27 January Junkers Ju 290 long-range reconnaissance bombers of the Fernaufklärungsgruppe 5 several times spotted and reported the combined OS.66/KMS.40 convoy and also the ON.221 convoy, and as a result U-212, U-271, U-281, U-571, U-592 and U-650 were grouped as the 'Hinein' wolfpack), and U-283, U-309, U-386, U-390, U-406, U-545, U-547, U-666, U-731, U-762, U-984, U-985 and U-989 as the 'Stürmer' (ii) wolfpack.
Air Vice Marshal C. R. Steele’s No. 15 Group of Air Chief Marshal Sir William Sholto Douglas’s RAF Coastal Command, reinforced by aircraft of Air Vice Marshal B. E. Baker’s No. 19 Group, flew many sorties against the wolfpacks in support of these convoys. Oberleutnant Emil Ranzau’s U-71 and Kapitänleutnant Curt Barleban’s U-271 were sunk on 28 January by a Short Sunderland flying boat of the RAAF’s No. 461 Squadron and a Consolidated Liberator long-range patrol bomber of the US Navy’s VP-103 squadron flying air cover for the SC.151 and ON.221 convoys.
On 29 January Oberleutnant Heinz Jaschke’s U-592 was damaged by a Liberator of the US Navy’s VP-102 squadron, and in transit back to a base in German-occupied France was sunk on 31 January by the sloops Starling, Magpie and Wild Goose of Captain F. J. Walker’s 2nd Support Group. Also on its transit back to France, Oberleutnant Paul-Heinrich Sass’s U-364 was sunk in the Bay of Biscay on 29 January by a Handley Page Halifax patrol bomber of the RAF’s No. 502 Squadron. During a 'Percussion' patrol, a Vickers Wellington medium-range anti-submarine aeroplane of the RAF’s No. 172 Squadron was shot down by U-608.
On 29 January the Germans broke off their anti-convoy operation, all the U-boats being recalled to France because of an invasion alarm, and when this proved false the boats were ordered to new positions.