British Vice-Admiral Horton’s submarine deployment pays off again. HMS Spearfish, patrolling in the Kattegat, encounters the already-damaged German cruiser Lützow returning from Oslo just after midnight. Spearfish fires a spread of 6 torpedoes then runs, not realizing that Lützow is unescorted. 1 torpedo hits Lützow nearly ripping off her stern. Lützow is towed back to Kiel but is out of action until repairs are complete in June 1941.
German success depends on reducing Norwegian Army resistance in southern Norway. The key is to link up their forces at Oslo and Trondheim via the long parallel mountain defiles. German 196th Division under General Richard Pellengahr moves North from Oslo up the Gudbrandsdal and Østerdal valleys with air support, brushing aside improvised Norwegian roadblocks.
General Kristian Laake is removed from command of the Norwegian Army for being defeatist and failing to mobilize his troops. He is replaced with General Otto Ruge. http://www.generals.dk/general/Laake/Kristian_Kristiansen/Norway.html