'DNU' was a British naval sweep off the coast of German-occupied Norway (23/24 October 1940).
The object of the undertaking was to locate and destroy significant quantities of German coastal shipping at a time when good nocturnal visibility was provided by the last of the October moon. The raid was entrusted to the destroyers Matabele, Punjabi and Somali, which departed Scapa Flow in the Orkney islands group at 11.20 on 22 October for Sullom Voe in the Shetland islands group, where they were to refuel and wait until the following evening before steaming to operate off Stadlandet; and by the light anti-aircraft cruisers Bonaventure and Naiad, which departed Rosyth at 10.00 on 23 October and were to operate off Egersund.
During 22 October, however, there was an unusual number of German aircraft reconnoitring the Shetland islands group, and German radio traffic indicated an important movement of surface forces down the Norwegian coast. In view of this activity the Admiralty considered an attack on the Shetland islands group might be imminent, so the three destroyers were ordered to patrol to the east of the Shetland islands group, and the Home Fleet’s battle-cruiser force was sailed to cover and support the raiding forces.
At 19.00 on 23 October, the destroyers were ordered to proceed toward a position off Egersund to intercept a group of 20 German fishing vessels supported by one escort ship. Here the destroyers captured and sank the German 391-ton weather ship WBS 5 (ex-trawler Adolf Vinnen), which was operating in the area to provide weather information for break-outs by the heavy cruiser (ex-pocket battleship) Admiral Scheer and heavy cruiser Hipper. Before the German vessel was sunk, its Enigma cipher machine and associated code books were seized.
Distant cover for 'DNU' was provided by a force, which departed Scapa Flow at 15.30 on 23 October, comprising the battle-cruisers Hood and Repulse, the light anti-aircraft cruisers Dido and Phoebe, and the destroyers Bulldog, Douglas, Isis, Keppel and Mashona.