This was a German relocation of U-boats to Norwegian bases for the protection of German-occupied Norway, which Adolf Hitler firmly believed to be an inevitable target for British invasion, and for deployment in the event of an Allied invasion of the European mainland (1 May/10 July 1944).
The main period of the combat associated with this grouping of U-boat strength was that between 3 June and 27 July. During the first part of this period, the air offensive by Air Vice Marshal S. P. Simpson’s No. 18 Group of Air Chief Marshal Sir William Sholto Douglas’s RAF Coastal Command continued against U-boats off Norway. Particularly involved were the Canadian Vickers Canso flying boats of the RCAF’s No. 162 Squadron, Consolidated Catalina flying boats of the RAF’s No. 210 Squadron, Catalina ‘boats and de Havilland Mosquito fighter-bombers of the RAF’s No. 333 (Norwegian) Squadron, Short Sunderland flying boats of the RAF’s No.330 (Norwegian) Squadron, and Consolidated Liberator long-range patrol bombers of the RAF’s Nos 86, 59 and 207 Squadrons.
On 3 June a Canso of No. 162 Squadron sank Oberleutnant Karl-Joachim Jenssen’s Schnorchel-equipped U-477. Patrols against U-boats were undertaken by the British submarines Visigoth (3/9 June), Stygian (4/17 June) and Subtle (25 June/10 July), but produced no results.
At the start of ‘Overlord’ on 6 June, the Germans halted the outbound passages of U-294, U-290, U-958, U-980 and U-1000, none of which was equipped with a Schnorchel. On 8 and 10 June the boats of the ‘Mitte’ wolfpack (U-242, U-276, U-397, U-677, U-745, U-975, U-982, U-987, U-999, U-998, U-1001, U-1007 and U-1156 were despatched to establish a defensive cordon off Norway’s west coast, and on 20/21 June U-317, U-396, U-771, U-994 and U-1192 arrived as the first wave of reliefs, with U-286, U-299 and U-319 following on 5 July as the second wave.
Of the outbound Schnorchel-fitted boats, Kapitänleutnant Helmut Röttger’s U-715 was sunk on 13 June by a Canso of No. 162 Squadron, which was itself then shot down by anti-aircraft fire. While on passage to Narvik, Oberleutnant Hilmar-Karl Shreyer’s U-987 was sunk to the west of the Lofoten islands by the British submarine Satyr. On 16 June U-998 was so badly damaged by the attack of a Mosquito of No. 333 Squadron that it had to be decommissioned on 27 June. On passage to a yard at which a Schnorchel could be fitted, U-804 was diverted to help U-998 but was itself attacked by another Mosquito of No. 333 Squadron and had to turn back because of the number of wounded on board. On 17 June Oberleutnant Klaus Hackländer’s U-423 was sunk by a Catalina of No. 333 Squadron and on 24 June Oberleutnant Ekkehard Scherraus’s U-1225 by a Canso of No. 162 Squadron, which was itself shot down. On 30 June Oberleutnant Rudolf Rademacher’s U-478 was sunk by a Liberator of No. 86 Squadron, which also failed to return, and a Catalina of No. 162 Squadron.
On 20 July U-863, outward bound to the Far East, was damaged by a Mosquito of No. 333 Squadron and had to turn back. On 25 July U-244, escorted by another vessel, came under attack from two Mosquito aircraft of No. 333 Squadron and was damaged. On 27 July U-865 was damaged by a Liberator of No. 86 Squadron and had to turn back; the Liberator was also badly damaged but managed to return to base. Kapitänleutnant Hermann Dahms’s U-980 of the ‘Mitte’ wolfpack was sunk by a Canso of No. 162 Squadron, which was then shot down on the following day by the anti-aircraft fire of another U-boat. On 14 June U-290 was damaged by a Mosquito of No. 333 Squadron, and six days later a Liberator of No. 86 Squadron damaged U-743, which had to turn back, but was itself also severely handled by the U-boat’s anti-aircraft fire. On 26 June a Liberator of No. 86 Squadron sank Oberleutnant Peter Rahlf’s U-317, but was itself damaged so badly by anti-aircraft fire that it had to be written off on return to base. On 28 June a Catalina of No. 210 Squadron damaged U-396. On 15 July a Liberator of No. 206 Squadron sank Oberleutnant Johannes Clemens’s U-319.
Of the U-boats of the ‘Eismeer’ wolfpack moving to create the ‘Trutz’ wolfpack, Oberleutnant Johann de Buhr’s U-347 succumbed to a Liberator of No. 86 Squadron and Kapitänleutnant Hans Seidel’s U-361 to a Catalina of No. 210 Squadron on 17 July. Oberleutnant Wolfgang Friedrich Freiherr von Forstner’s U-742 was sunk on 18 July by a Catalina of No. 210 Squadron, but the flying boat later had to make an emergency alighting as a result of the damage it had sustained from anti-aircraft fire. On 19 July U-968 was damaged by a Liberator of No. 86 Squadron, U-716 by a Liberator of No. 59 Squadron and U-387 by a Sunderland of No. 330 Squadron.