Churchill was concerned about German naval activity in the Baltic Sea and initially wanted to send a naval force there but this was soon changed to a plan, codenamed Operation Wilfred, to mine Norwegian waters and stop iron ore shipments from Narvik to Germany. There were disagreements about mining, both in the war cabinet and with the French government. As a result, Wilfred was delayed until 8 April 1940, the day before the German invasion of Norway was launched.
Operation Wilfred was a British naval operation during the Second World War that involved the mining of the channel between Norway and her offshore islands to prevent the transport of Swedish iron ore through neutral Norwegian waters to be used to sustain the German war effort. The Allies assumed that Wilfred would provoke a German response in Norway and prepared a separate operation known as Plan R 4 to occupy Narvik and other important locations. On 8 April 1940, the operation was partly carried out, but was overtaken by events as a result of the following day′s German invasion of Norway and Denmark (Operation Weserübung), which began the Norwegian Campaign.
The Norwegian campaign was an attempted Allied occupation of northern Norway, during the early stages of World War II. Resulted evacuation of the Norwegian government and the royal family, establishment of the Norwegian armed forces from the exile. The 62 days of fighting made Norway the nation that withstood a German land invasion for the second longest period of time, after the Soviet Union.
On 9 April, German forces invaded Denmark and Norway. On the same day Hitler proclaimed the birth of the Greater Germanic Reich, his vision of a united empire of Germanic nations of Europe in which the Dutch, Flemish, and Scandinavians were joined into a "racially pure" polity under German leadership.
In 1940 the entire royal family had to flee Oslo because of the German invasion. It was deemed safer for the family to split up. The King and Crown Prince Olav would remain in Norway and the Crown Princess was to make her way to Sweden with the three children. The latter party reached Sweden on the night of 10 April. but although Crown Princess Märtha was Swedish-born, they encountered problems at the border station.