'Mordbrenner' was a U-boat wolfpack operation off Newfoundland against convoys, including SC.52, on passage from North America to the UK (16 October/13 November 1941).

The wolfpack comprised U-109, U-208, U-374 and U-573, and for the loss of none of its own number sank two ships (7,221 tons).

These boats, which had not been involved in the attack on the SC.48 convoy, were formed into the 'Mordbrenner' wolfpack and despatched to undertake a reconnaissance of the area near the Strait of Belle Isle. The boats arrived on 20 October but found no Allied shipping. After intercepts of the boats' radio transmissions, which made it possible to establish their positions, the Allies routed their convoys farther to the south to avoid attack.

From 28 October the U-boats moved to the area south-west of Newfoundland, and from 31 October were ordered toward the ON.28 convoy, which was being shadowed by the boats of the 'Reissewolf' pack from the previous day. Oberleutnant Unno von Fischel' s U-374 sank the 3,349-ton British Rose Schiaffino, an independent sailer, and then on 1 November sighted the SC.52 convoy. Ordered to support elements of the 'Reissewolf' and 'Stosstrupp' wolfpacks in attacks on the SC.50 convoy, the boats of the 'Mordbrenner' pack were unable to approach the convoy, and started their voyage back to base on 3 November after Oberleutnant Alfred Schlieper' s U-208 had sunk the 3,872-ton British Larpool, a straggler of the ON.27 convoy, on 2 November.