the middle of the month, severe ice forced the ship to remain in port. On 5 April, she was deemed to be ready for action, and was therefore assigned to the forces participating in the invasion of Norway. Operation Weserübung On 5 April 1940, Konteradmiral (Rear Admiral) Oskar Kummetz came aboard the ship while she was in Swinemünde. An 800-strong detachment of ground troops from the 163rd Infantry Division also boarded. Three days later, on 8 April, Blücher left port, bound for Norway; she was the flagship for the force that was to seize Oslo, the Norwegian capital, Group 5 of the invasion force. She was accompanied by the heavy cruiser Lützow, the light cruiser , and several smaller escorts. The British submarine spotted the convoy steaming through the Kattegat and Skagerrak, and fired a spread of torpedoes; the Germans evaded the torpedoes, however, and proceeded with the mission. Night had fallen by the time the German flotilla reached the approaches to the Oslofjord. Shortly after 23:00 (Norwegian time), the Norwegian patrol boat spotted the flotilla. The German torpedo boat attacked Pol III and set her on fire, but not before the Norwegian patrol boat raised the alarm with a radio report of being attacked by unknown warships. At 23:30 (Norwegian time) the south battery on Rauøy spotted the flotilla in the searchlight and fired two warning shots. Five minutes later, the guns at the Rauøy battery fired four rounds at the approaching Germans, but visibility was poor and no hits were scored. The guns at Bolærne fired only one warning shot at 23:32. Before Blücher could be targeted again, she was out of the firing sector of these shore guns and was seen no more by them after 23:35. The German flotilla steamed on at a speed of . Shortly after midnight (Norwegian time), an order from the Commanding Admiral to extinguish all lighthouses and navigation lights was broadcast over the NRK (Norsk rikskringkasting) [Norwegian Broadcasting Corporation]. The German ships had been ordered to fire only in the event they were directly fired on first. Between 00:30 and 02:00, the flotilla stopped and 150 infantrymen of the landing force were transferred to the escorts R17 and R21 (from Emden) and R18 and R19 (from Blücher). Battle of Drøbak Sound R boats were ordered to engage Rauøy, Bolærne and the naval port and city of Horten. Despite the apparent loss