'Karin' (i) was a German naval minelaying operation off the Porsangerfjord of German-occupied Norway (19/20 March 1942).
The undertaking had to be postponed from 16/17 March as a result of adverse weather, but was then completed by the minelayer Ulm.
Although she had been completed in 1938 as a banana carrier for the Norddeutscher Nord shipping line, the 3,100-ton Ulm had been impressed for German naval service as a minelayer with the capacity for between 240 and 270 mines, and thus represented a distinct threat to the Allied convoys plying the Arctic route to and from the USSR’s northern ports. In the aftermath of the disastrous PQ.17 convoy, supported by 'EU', the US heavy cruiser Tuscaloosa, on loan to the British Home Fleet together with the US destroyers Emmons and Rodman, departed Murmansk to return to Scapa Flow in the Orkney islands group during the course of 24 August, arriving with the survivors of PQ.17 on 28 August. At the same time the British destroyers Marne, Martin and Onslaught also departed Murmansk but were then detached, on the basis of 'Ultra' intelligence, to make a sweep toward the north coast of German-occupied Norway.
'Ultra' had established on 19 August that Ulm was approaching Narvik from the south and then, on 25 August, that she was to head for Novaya Zemlya to lay a major minefield off the island’s north-west coast. On 28 August, the three British destroyers intercepted Ulm off Bjørnøya: one of the British torpedoes hit Ulm's ammunition storage, triggering a huge explosion after which the German ship broke up and sank in just 150 seconds with the loss of 114 men; there were 60 survivors.
The sinking of Ulm greatly reduced the threat of major German minelaying operations in the path of the Arctic convoys, and at the beginning of October 'Ultra' revealed that the Germans were having to use the heavy cruiser Admiral Hipper as an interim minelayer off Novaya Zemlya.