'Seeräuber' (i) was a U-boat wolfpack operation in the Atlantic against the HG.76 convoy (14/23 December 1941).
The wolfpack comprised U-67, U-71, U-107, U-108, U-125, U-127, U-131, U-434, U-567 and U-574, and for the loss of four of its own number sank three ships (8,810 tons).
The HG.76 convoy comprised 32 ships, some unladen and others carrying trade goods, homebound to the UK from Gibraltar. There was a strong escort comprising Commander F. J. Walker’s recently formed 36th Escort Group (sloops Stork and Deptford and corvettes Convolvulus, Gardenia, Marigold, Penstemon, Rhododendron, Samphire and Vetch, currently strengthened by the new escort carrier Audacity and her escorting destroyers Blankney, Stanley and Exmoor II as well as other warships in the form of the sloops Fowey and Black Swan, and the corvettes Carnation and Free French Malouine).
Against this British strength was ranged a wolfpack initially comprising U-67, U-107, U-108, U-127, U-131, U-434 and U-574, later strengthened by the arrival of U-71, U-125 and U-567.
The HG.76 convoy departed Gibraltar on 15 December, and was reported almost immediately by German agents across Algeciras Bay in neutral Spain, from which were reported the convoy’s composition, escort strength and departure time. The convoy was also sighted later on the same day by Kapitänleutnant Eitel-Friedrich Kentrat’s U-74, which was in transit to the Mediterranean, but was then lost in poor visibility, while the U-boat command in Germany was confused by an agent’s report that the convoy had returned to port.
The wolfpack was disposed in a patrol line to the south of Cape St Vincent, but the HG.76 convoy was able to pass through the line without detection. Meanwhile Korvettenkapitän Bruno Hansmann’s U-127 was detected in a routine anti-submarine sweep by four destroyers from Gibraltar and in a brief attack was destroyed, the credit going to the Australian destroyer Nestor. On 16 December the HG.76 convoy was sighted by a Focke-Wulf Fw 200 Condor reconnaissance bomber patrolling from Bordeaux, and on the basis of the aerial sighting report U-108 made contact and shadowed the convoy as the rest of the wolfpack moved in.
During the night of 16/17 December the wolfpack closed on the convoy, and by the morning of 17 December four U-boats were in contact. However, vigorous patrolling by the escorts, and the activity of aircraft from Audacity, led to the detection of Korvettenkapitän Arend Baumann’s U-131, which was depth-charged by Stork, with Penstemon and the three destroyers in concert. The boat was driven to the surface and sunk, though not before shooting down one of Audacity's Grumman Wildcat fighters.
During the night of 17/18 December the boats attacked once again, but were denied by the escort force in a process of aggressive countermeasures which prevented any torpedo hits on the Allied ships. At dawn on 18 December Kapitänleutnant Wolfgang Heyda’s U-434 was sighted by the destroyers, attacked and rammed by Blankney, which was damaged in the process. During the rest of the day several of the escorts had to leave: the sloops Black Swan and Fowey and corvettes Carnation and Malouine returned to Gibraltar to refuel, while Blankney departed for repairs, escorted by Exmoor II.
During the night of 18/19 December Stanley sighted Oberleutnant Dietrich Gengelbach’s U-574 astern, shadowing the convoy. The destroyer attacked, but was herself torpedoed and sunk. Stork and Samphire followed up the destroyer’s attack and sank U-574 before rescuing British and German survivors. During this same night Korvettenkapitän Klaus Scholtz’s U-108 attacked successfully, torpedoing the 2,869-ton British Ruckinge, which was abandoned and later sunk by Samphire.
On 19 December the convoy was attacked by a force of Condor warplanes, which inflicted no damage but lost two of their own number shot down and another damaged by Wildcat fighters from Audacity. On the same day the wolfpack received the news that it was to be supplemented, from 21 December, by three more U-boats from Bordeaux, namely Korvettenkapitän Walter Flachsenberg’s U-71, the 'ace' Kapitänleutnant Engelbert Endrass’s U-567, and Kapitänleutnant Gerhard Bigalk’s U-751. Over the next three days the three remaining 'Seeräuber' (i) boats (Kapitänleutnant Günther Müller-Stückheim’s U-67, Oberleutnant Harald Gelhaus’s U-107 and Korvettenkapitän Klaus Scholtz’s U-108) continued to shadow and attack when there was any opportunity, but without result.
On 21 December the three boats from Bordeaux arrived and the enlarged wolfpack prepared to attack once more. Walker attempted to draw off the attack by having Deptford make a demonstration at a distance from the convoy. This was unsuccessful, as some of the merchant ships were confused by the display, and also fired star shells, revealing their position. U-567 sank the 3,324-ton Norwegian Annavore, U-751 sighted Audacity as the escort carrier zigzagged behind the convoy without escort: Bigalk fired and three torpedoes struck Audacity, which sank. Marigold, Vetch and Samphire counterattacked without result. Later in the same night Deptford spotted a U-boat on the surface, attacked and dropped depth charges as the boat dived. There was no apparent result, but post-war analysis revealed that U-567 had been sunk. After this Deptford was in collision with Stork, both vessels being damaged.
During 22 December U-71 and U-751 remained in contact, to be joined by Kapitänleutnant Ulrich Volkers’s U-125 (in transit to the east coast of the USA for 'Paukenschlag'), while the convoy’s escort was reinforced by the destroyers Vanquisher and Witch.
On 23 December Vizeadmiral Karl Dönitz, the Befehlshaber der Unterseeboote, was sufficiently disturbed by the combination of losses and lack of success to call off the attack. U-67, U-107, U-108 and U-751 returned to bases in France. Despite the loss of Audacity and the three other ships, the safe arrival of 30 ships and the destruction of three U-boats (U-127 was not included and U-567 was not confirmed until after the war) was judged to be an outstanding victory. It also confirmed Walker as the foremost Allied practitioner of anti-submarine warfare. By contrast Dönitz and the U-boat arm had been shaken by their losses at this time, particularly that of Endrass, the leading U-boat ace of the time with a tally of 22 ships sunk (118,528 gross registered tons) and another four damaged.