This was a U-boat wolfpack operation in the Atlantic against the HG.84 convoy (11/16 June 1942).
Named for Kapitänleutnant Engelbert Endrass, the ‘ace’ U-boat captain (22 ships totalling 118,528 tons), who had been killed on 21 December 1941, the wolfpack comprised U-71, U-84, U-89, U-132, U-134, U-437, U-552, U-571 and U-575, and for the loss of none of its own number sank five ships (15,858 tons), which all succumbed to attacks by Korvettenkapitän Erich Topp’s U-552.
The departure of the HG.84 convoy of 23 merchant vessels from Halifax, Nova Scotia, supported by Commander F. J. Walker’s 36th Escort Group (sloop Stork and corvettes Convolvulus, Gardenia and Marigold) was reported by German agents on 9 June. The Germans initially concentrated on air reconnaissance to fix the convoy’s location, and this task was undertaken by Hauptmann Edmund Daser’s I/Kampfgeschwader 40, one of whose Focke-Wulf Fw 200 Condor long-range maritime reconnaissance bombers reported the convoy on 11 June and managed to escape being shot down by the Hawker Sea Hurricane fighter launched from the catapult aircraft merchantman Empire Moon.
Eight outward-bound U-boats received orders from Admiral Karl Dönitz, commander of the U-boat arm, to operate as the ‘Endrass’ pack from 14 June. In the afternoon of that day an Fw 200 spotted the convoy and vectored U-552 and then U-89 and U-132 toward it. The U-boats were, however, driven off by Stork, Gardenia and Marigold.
Knowing that Stork must soon move off to catch up with the convoy, U-552 was able to operate on the basis of reports from U-437, which had meanwhile come up but then been driven off by Convolvulus. During the night of 14/15 June U-552 sank three ships (2,759-ton British City of Oxford, 1,943-ton British Etrib and 1,346-ton British Pelayo), and then another two ships (7,374-ton Norwegian Slemdal and 2,436-ton British Thurso) in two attacks.
During daylight on 15 June U-71, U-84 and U-575 were driven off by the Allied air escort; and during the following night U-71, U-84 and U-552 were driven off by Stork, Marigold and Convolvulus, and U-575 missed the convoy with a salvo of five torpedoes fired at great range. Although U-571 and two Fw 200 aircraft re-established contact during the morning of 16 June, the operation was then broken off as totally calm weather, with good visibility, reversed the tactical advantage to the Allied naval and air escorts.
Others ships of the 36th Escort Group sent to assist Walker’s diminished command, consisting of the destroyers Beagle and Wild Swan, frigate Spey and Free Polish escort destroyer Krakowiak, came under attack in the evening of 17 June from aircraft of Major Ghert Roth’s Küstenfliegergruppe 106, which damaged Wild Swan. This old destroyer later sank after colliding with a Spanish trawler.