This was a U-boat wolfpack operation in the North Atlantic against the SC.126, HX.234 and ONS.4 convoys (11/27 April 1943).
The first seven boats of this pack assembled as early as 11 April, and were later joined by another 13 boats, and in overall terms, therefore, the wolfpack comprised U-71, U-84, U-108, U-134, U-188, U-191, U-192, U-203, U-209, U-257, U-258, U-267, U-306, U-378, U-381, U-404, U-413, U-415, U-438, U-531, U-532, U-552, U-571, U-598, U-610, U-613, U-618, U-631, U-648, U-662, U-706, U-732 and U-954. For the loss of Korvettenkapitän Hellmut Kurrer’s U-189 and Kapitänleutnant Helmut Fiehn’s U-191, the U-boats of this wolfpack sank five ships (30,822 tons) and damaged another two (10,799 tons) in attacks on the ONS.3, ONS.178 and HX.234 convoys.
It was from 11 April that seven U-boats were deployed in an area to the east of Newfoundland as the ‘Meise’ wolfpack, and then more boats replenished from the tankers U-462 and U-463 supplemented the initial boats to allow the establishment of a patrol line from 14 April for the interception of the SC.126 convoy. This comprised 38 ships and was supported by Commander R. C. Boyle’s British Escort Group B5 (destroyer Havelock, frigate Swale, and corvettes Buttercup, Godetia, Lavender, Pimpernel and Saxifrage). Further shielded by the 3rd Escort Group (destroyers Offa, Impulsive, Penn and Panther), the convoy was routed to the south of the ‘Meise’ wolfpack’s patrol line and thus avoided interception.
On 19 April, en route to their new positions, U-732 and U-108 each reported the sinking of one ammunition transport from an Icelandic feeder convoy, and the sinking of this vessel, the 7,176-ton US Robert Gray, in generally credited to the latter boat.
In the light of B-Dienst intelligence on 20 April, the ‘Meise’ pack, now of 21 U-boats, was relocated to a position ahead of the HX.234 convoy. On 21 April U-306 spotted and reported the convoy, which was supported by Commander E. C. Day’s British Escort Group B4 (destroyers Highlander, Beverley and Vimy, and corvettes Pennywort, Anemone, Abelia, Asphodel, Clover and Rosthern), and sank the 10,218-ton British Amerika during the night. While closing up, U-706 met the ONS.3 convoy supported by the 40th Escort Group (sloops Aberdeen, Hastings and Lulworth, and frigates Moyola and Waveney). U-203, U-415, U-191, U-613 and U-438 moved toward an attack position, and the last of this boats also met the following ON.178 convoy of 18 ships supported by Commander E. C. Bayldon’s British Escort Group B1 (destroyers Hurricane and Watchman, frigate Kale, and corvettes Dahlia, Meadowsweet, Wallflower and Monkshood). From this convoy Oberleutnant Kurt Neide’s U-415 sank the 4,917-ton British Ashantian and damaged the 5,486-ton British Wanstead, which was later sent to the bottom by Kapitänleutnant Gustav Poel’s U-413. Kapitänleutnant Helmut Fiehn’s U-191 sank the 3,025-ton Norwegian Scebeli before contact was lost following the arrival of the 3rd Support Group to support the two convoys.
The SC.127 convoy, supported by the Canadian Escort Group C1, was first re-routed to the south, but the signal ordering this change was intercepted and decrypted by the B-Dienst on 20 April, resulting in the formation of the new ‘Specht’ wolfpack for establish a patrol line with 17 boats on 22 April. The SC.127 convoy was then ordered to circumvent this pack in the gap between the ‘Specht’ and ‘Meise’ wolfpacks. On 22 April Consolidated Catalina flying boats of the US Navy’s VP-84 squadron based in Greenland and Iceland drove the boats of the ‘Meise’ wolfpack away from the HX.234 convoy, only Kapitänleutnant Claus von Trotha’s U-306 maintaining contact and sinking the 10,218-ton British Amerika in a submerged daylight attack on 22 April. U-954 torpedoed and damaged the 5,313-ton British Silvermaple before the arrival of the air escort in the form of Consolidated Liberator long-range patrol bombers of the RAF’s No. 120 Squadron, one of which sank Kurrer’s U-189.
U-732 now encountered the oncoming ONS.4 convoy of 41 ships supported by Commander D. G. F. W. MacIntyre’s British Escort Group B2 (destroyers Hesperus, Whitehall and Vanessa, and corvettes Clematis, Sweetbriar, Gentian and Heather). This and the nearby ON.179 convoy, the latter supported by Lieutenant Commander E. H. Chavasse’s Canadian Escort Group C2 (British destroyer Broadway, British frigate Lagan, corvettes Amherst, Drumheller, Morden and Primrose, and corvettes Algoma and Calgary returning from ‘Torch’ service) were further supported by Captain E. M. C. Abel-Smith’s 5th Support Group (escort carrier Biter and destroyers Pathfinder, Obdurate and Opportune). Fairey Swordfish anti-submarine aircraft from Biter forced U-732 to submerge.
Fiehn’s U-191, which had taken over as the contact-keeper boat, was located with HF/DF by Hesperus and sunk. Of the shadowing U-954, U-209, U-648, U-108, U-404 and U-514, only U-108 managed to establish contact with the convoy, and only U-404 with the escort group. In the morning of 25 April U-404 fired a torpedo salvo against what the U-boat’s crew believed to be the US light carrier Ranger but was in fact Biter, but the torpedoes were wrongly fused and therefore failed.
On the same day a Swordfish of the FAA’s No. 811 Squadron from Biter sighted Kapitänleutnant Hermann Koltmann’s U-203, which was returning to base and was now sunk by Pathfinder.
The 11 boats of the ‘Meise’ wolfpack stationed near HX.234 were unable to attack during the night of 23/24 April as a result of hail, rain and snowstorms combined with the skilful manoeuvring of the convoy. U-306 maintained contact on 24 April, but the presence of a strong air escort for HX.234 and ONS.5, the latter close to the north, allowed only U-610 to make an attack, which was unsuccessful, and while making for the HX.234 convoy Oberleutnant Dietrich von Carlewitz’s U-710 was sunk by a Boeing Fortress long-range patrol bomber of the RAF’s No. 206 Squadron. After a miss by U-413 in the night, the remaining boats were driven off by the air escort and the reinforced sea escort, now including the 4th Escort Group (destroyers Faulknor, Eclipse, Fury and Icarus).