'Blücher' (iv) was a U-boat wolfpack operation in the Atlantic Ocean (14/28 August 1942).

The wolfpack comprised U-107, U-214, U-333, U-406, U-566, U-590, U-594 and U-653, and for the loss of none of its own number sank six ships (41,984 tons) and damaged one armed merchant cruiser, the 10,552-ton British Cheshire, of the SL.118 convoy. Formed on 13 July, the wolfpack attacked the SL.118 and SL.119 convoys steaming from Freetown, Sierra Leone to Liverpool.

Kapitänleutnant Gerhard Remus’s U-566 was the first boat to attack, in a position to the north-east of the Azores islands group. At 17.56 on 17 August the U-boat fired three torpedoes at the SL.118 convoy, hitting the 6,607-ton Norwegian Triton twice and sinking her. The master, 39 crewmen, two gunners and one passenger abandoned ship, and were picked up by the 3,496-ton British Baron Dunmore. At 18.52 on 18 August Kapitänleutnant Günther Reeder’s U-214 fired four single torpedoes at the SL.118 convoy and hit three ships: one torpedo damaged the 10,552-ton armed merchant cruiser Cheshire, which was towed back to the UK for repairs; another damaged the 7,522-ton British Hatarana so badly that she was abandoned by her crew of 108 and sunk by the gunfire of the corvette Pentstemon; and the last two struck the 6,318-ton Dutch Balingkar, sinking her within 15 minutes with the loss of two men from her crew of 93.

At 16.22 on the next day Kapitänleutnant Horst Dieterichs’s U-406 torpedoed the 7,452-ton British City of Manila, which was then abandoned by her crew. On the next day the vessel was reboarded by a number of her crew, but the ship later broke in two, was abandoned again and then sank. One crew member was lost. The master, 83 crewmen and 11 gunners were rescued.

At 19.08 on 28 August Kapitänleutnant Gerhard Remus’s U-566 fired a spread of three torpedoes at the SL.119 convoy to the west-north-west of Lisbon and hit two ships, the 5,661-ton British City of Cardiff and the 8,424-ton Dutch Zuiderkerk. The latter was hit in the bows and forced to stop so that the damage could be inspected. The ship then managed to rejoin the convoy, but flooding in her holds forced the 56 crew and 12 passengers to abandon ship early on 29 August, and the ship was then sunk with depth charges by the sloop Erne. Meanwhile, the badly damaged City of Cardiff remained afloat, but foundered two days later with the loss of 21 crew.