'Löwenherz' was a U-boat wolfpack operation in the Atlantic against the HX.231 convoy (1/10 April 1943).
The wolfpack comprised U-168, U-191, U-260, U-270, U-563, U-564, U-572, U-584, U-592, U-594, U-630, U-632, U-635 and U-706, and for the loss of Korvettenkapitän Hans Karpf’s U-632 and Oberleutnant Heinz Eckelmann’s U-635 sank four ships (28,083 tons) and damaged another three ships in attacks on the HX.231 convoy.
The 'Löwenherz' wolfpack was created in the area to the south-east of Greenland from U-168, U-191, U-260, U-270, U-563, U-564, U-572, U-584, U-592, U-594, U-630, U-632, U-635 and U-706 coming from the attack on the HX.230 convoy after being replenished at sea by U-463. On 4 April the returning U-530 sighted the HX.231 convoy just to the west of the wolfpack’s patrol line.
The convoy comprised 61 ships supported by Commander P. W. Gretton’s British Escort Group B7 ( frigate Tay, destroyer Vidette, and corvettes Alisma, Pink, Snowflake and Loosestrife).
To supplement the efforts of the 'Löwenherz' wolfpack, the nearby U-229 and U-532 were also deployed against the HX.231 convoy. U-530 brought up five boats before dusk and two more during the night, and during this period Oberleutnant Heinz Eckelmann’s U-635 sank the 5,529-ton British Shillong, and Oberleutnant Werner Winkler’s U-630 the 9,365-ton British Waroonga, while Oberleutnant Robert Schetelig’s U-229 sent down the 3,406-ton Swedish Valaaren, which was a straggler from the HX.231 convoy. While trying to get into an attack position, U-572 was rammed and damaged.
On 5 April the arrival of Consolidated Liberator long-range patrol bombers of the RAF’s No. 86 Squadron forced U-260, the contact-keeper, to dive and thereby lose contact with the convoy. Kapitänleutnant Götz von Hartmann’s U-563 torpedoed and damaged the 9,005-ton US tanker Sunoil, which Kapitänleutnant Kurt Lange’s U-530 later sent to the bottom. On 5 April Eckelmann’s U-635 was sunk by a Liberator of the RAF’s No. 120 Squadron, but in the afternoon of the same day Kovettenkapitän Alexander von Zitzewitz’s U-706 sank the 7,124-ton British British Ardour. During the night of 5/6 April Karpf’s U-632 sank another straggler, the 7,065-ton Dutch Blitar, and then, after missing Alisma, was itself sunk on 6 April by a Liberator of the RAF’s No. 86 Squadron. Tay attacked and slightly damaged U-306 before it could reach a firing position. U-594 was damaged by a Liberator of No. 120 Squadron. The attacks of U-270 and U-134 were unsuccessful.
Also on 6 April, the 4th Escort Group (destroyers Inglefield, Fury, Eclipse and Icarus) made touch with the convoy and, together with the air escort, drove off the contact-keeping U-270, U-229, U-564, U-134, U-563 and, during the morning of 7 April, U-260.
Meanwhile the ON.175 convoy, supported by the US Escort Group A3 (US Coast Guard cutter Spencer, US destroyer Greer, British corvette Dianthus, and Canadian corvettes Dauphin, Rosthern and Trillium) passed without detection.