Hitler meanwhile had decided he would have to take Norway. He was worried that the British might come to the aid of Finland, land at Narvik and seize the Swedish iron-mines at Gallivare from which Germany received supplies of iron ore, vital for German's armaments industry. The Allies did indeed intend to invade Norway with the Norwegians' approval, it was hoped even though the Finnish war had ended, but they waited too long and the Germans got there first on April 1940.

German troops carried by warship took Narvik, Trondheim and Bergen. Paratroops (troops dropped by parachute) took Oslo and Stavanger. Denmark was overrun in a few hours, providing the Germans with bases for providing air support. The German forces were modest in scale but they moved swiftly with strong air cover.

The British Home Fleet, which was much stronger than the German fleet, sailed too late and, without air cover, could not stop the German invasion of Norway. But the British managed to sink many German warships and greatly reduced the strength of the German navy.

British troops landed north and south of Trondheim and near Narvik. Short of air cover, the better -equipped and better-trained Germans coming up from Oslo defeated them and the Norwegians, who soon conquered the country. The British forces withdrew in May 1940.

The Norwegian campaign was a great success for the Germans. It saved them from the sort of North Sea blockade that had been fatal for them in World War One and provided them with a base from which to attack Allied shipping.

In Britain a majority of MPs blamed Neville Chamberlain for the humiliating British defeat and voted against him in the House of Commons. Winston Churchill was chosen as the new Prime Minister. However Germanys Navy was made less effective at Dunkirk than it might have been.