section_path: History/Second World War
section_name: Second World War
paragraph_text: Second World War
  
  Norway once more proclaimed its neutrality during the Second World War, but was invaded by German forces on 9 April 1940. Although Norway was unprepared for the German surprise attack (see: Battle of Drøbak Sound, Norwegian Campaign, and Invasion of Norway), military and naval resistance lasted for two months. Norwegian armed forces in the north launched an offensive against the German forces in the Battles of Narvik, but were forced to surrender on 10 June after losing British support which had been diverted to France during the German invasion of France.
  
  King Haakon and the Norwegian government escaped to Rotherhithe in London. Throughout the war they sent radio speeches and supported clandestine military actions against the Germans. On the day of the invasion, the leader of the small National-Socialist party Nasjonal Samling, Vidkun Quisling, tried to seize power, but was forced by the German occupiers to step aside. Real power was wielded by the leader of the German occupation authority, Josef Terboven. Quisling, as minister president, later formed a collaborationist government under German control. Up to 15,000 Norwegians volunteered to fight in German units, including the Waffen-SS.
  
  Many Norwegians and persons of Norwegian descent joined the Allied forces as well as the Free Norwegian Forces. In June 1940, a small group had left Norway following their king to Britain. This group included 13 ships, five aircraft, and 500 men from the Royal Norwegian Navy. By the end of the war, the force had grown to 58 ships and 7,500 men in service in the Royal Norwegian Navy, 5 squadrons of aircraft in the newly formed Norwegian Air Force, and land forces including the Norwegian Independent Company 1 and 5 Troop as well as No. 10 Commandos.
  
  During German occupation, Norwegians built a resistance movement which incorporated civil disobedience and armed resistance including the destruction of Norsk Hydro 's heavy water plant and stockpile of heavy water at Vemork, which crippled the German nuclear programme. More important to the Allied war effort, however, was the role of the Norwegian Merchant Marine, the fourth-largest merchant marine fleet in the world. It was led by the Norwegian shipping company Nortraship under the Allies throughout the war and took part in every war operation from the evacuation of Dunkirk to the Normandy landings. Every December Norway gives a Christmas tree to the United Kingdom as thanks for the British assistance during the war.
  
  Svalbard was not occupied by German troops, but Germany secretly established a meteorological station there in 1944.