'Panther' (iv) was a U-boat wolfpack operation in the Atlantic against the ONS.148 and HX.217 convoys (29 November/11 December 1942).

The wolfpack was formed in the central Atlantic from the newly arrived U-135, U-211, U-254, U-439, U-465, U-524 and U-758 to locate and attack the ONS.148 convoy supported by the British Escort Group B2.

The wolfpack moved to the west in the direction of the area to the north-east of Newfoundland until 4 December, but located no targets. On 4 December U-524, which was carrying a B-Dienst radio intercept and decryption team, intercepted the convoy’s radio traffic, and was thus able to direct the wolfpack to the north-east, and at about 12.00 on 6 December the boat sighted the HX.217 convoy of 33 ships supported by Commander R. Heathcote’s British Escort Group B6 (destroyers Fame and Free Polish Burza, corvettes Vervain and Free Norwegian Eglantine, Potentilla and Rose, and HF/DF-equipped rescue ship Perth).

The four U-boats which approached in the afternoon of 6 December then lost contact as the visibility worsened, and were also distracted by the destroyer Montgomery of the Western Local Escort Force, which was launching flares away to one flank.

In the morning of 7 December Kapitänleutnant Walter Freiherr von Steinaecker’s U-524 again established contact and brought up U-135, U-254, U-439 and U-465, but the boats were then driven off by a Consolidated Liberator long-range patrol bomber of the RAF’s No. 120 Squadron. During the night of 7/8 December von Steinaecker’s U-524 sank the 8,194-ton British Empire Spenser, and just missed Fame. U-254, U-465, U-623 (arriving with U-611 after refuelling) and U-758 were located by Burza, Eglantine, Potentilla and Rose before being able to reach a firing position, and were driven off.

On 8 December the 'Draufgänger' (i) wolfpack’s boats (U-221, U-455, U-553, U-569, U-604, U-600, U-609, U-610 and U-615) neared the area, Kovettenkapitän Bernhard Zurmühlen’s U-600 having already sunk the 6,762-ton US James McKay, a straggler from the HX.217 convoy, on 7/8 December. On 8 December Kapitänleutnant Nikolaus von Jacobs’s U-611 was sunk by a Liberator of No. 120 Squadron. In the afternoon of the same day U-610 and U-553 established contact but, after a miss on a destroyer, they and another three boats were compelled to dive by the appearance overhead of two Liberator aircraft of No. 120 Squadron. During the evening of 8 December Oberleutnant Hans-Hartwig Trojer’s U-221 inadvertently rammed and sank Kapitänleutnant Odo Loewe’s U-254. Two boats were driven off by Potentilla and Rose.

During the morning of 9 December U-455 attacked but missed an escort, and Korvettenkapitän Karl Thurmann’s U-553 sank the 5,273-ton British Charles L. D., a straggler from the HX.217 convoy. Another two attacks were prevented by Eglantine and Potentilla. During the day U-553 maintained contact.

During the night of 9/10 December only U-758 was able to attack, but missed Burza. Six other attacks were checked by Potentilla (twice), Rose, Vervain, Burza and Rose. Despite the strong Allied air cover, provided by six Lockheed Hudson medium-range patrol bombers of the RAF’s No. 269 Squadron, Boeing Fortress long-range patrol bombers of the RAF’s No. 220 Squadron and Consolidated Catalina flying boats of the US Navy’s VP-84 squadron, U-628 was able to keep contact until the night of 11 December. However, U-610, U-615 and U-623 were driven off, and U-609 was slightly damaged by a Catalina of the RAF’s No. 84 Squadron.

A resumption of the attack on 11 December had no prospect of success as a result of the presence of Allied air cover, and the Germans therefore terminated their operation.