The German invasion of Denmark (), was the German attack on Denmark on 9 April 1940, during the Second World War. The attack was a prelude to the invasion of Norway (, 9 April – 10 June 1940). Denmark's strategic importance for Germany was limited. The invasion's primary purpose was to use Denmark as a staging ground for operations against Norway, and to secure supply lines to the forces about to be deployed there. An extensive network of radar systems was built in Denmark to detect British bombers bound for Germany. The attack on Denmark was a breach of the non-aggression pact Denmark had signed with Germany less than a year earlier. The initial plan was to push Denmark to accept that German land, naval and air forces could use Danish bases, but Adolf Hitler subsequently demanded that both Norway and Denmark be invaded. Denmark's military forces were inferior in numbers and equipment, and after a short battle were forced to surrender. After less than two hours of struggle, Danish Prime Minister Thorvald Stauning ended the opposition to the German attack, for fear that the Germans would bomb Copenhagen (København), as they had done with Warsaw during the invasion of Poland in September 1939. Due to communication difficulties, some Danish forces continued to fight, but after a further two hours, all opposition had stopped. Lasting approximately six hours, the German ground campaign against Denmark was one of the shortest military operations of the Second World War. Background The attack on Denmark was part of Operation Weserübung Süd, Germany's plan for the invasion of Norway. Its main purpose was to secure the iron ore that shipped from Narvik. To capture Norway, the Germans had to control the port outside Aalborg (Ålborg) in northern Jutland (Jylland). The Kriegsmarine high command approved of occupying Denmark to extend the German sea-defence network northward, making it harder for British ships to outflank it from the north when attacking ships in the Atlantic. Norway's fjords also provided excellent bases for German submarines in the North Atlantic. The Germans presented the invasion as an act of protection against a supposed imminent attack by the United Kingdom. German plan of attack The German High Command planned a combined assault on Denmark to overrun the country as swiftly as possible. It included an airborne assault on the Aalborg (Ålborg) airfields, a surprise landing of infantry from naval auxiliaries at