Norway's declaration of neutrality was of little significance. On 9 April 1940, German forces attacked Norway. After an intense two-month struggle, and despite military assistance from Great Britain and France, Norway had no choice but to surrender. The Royal Family, the Government and some of the heads of the Ministry of Defence and the civil administration left for Great Britain, along with the withdrawing Allied troops. During the war the Norwegian government conducted its activities in exile.
The most important resource that the Norwegians had to offer the Allies was the Norwegian merchant fleet. It consisted of more than 1,000 ships, aggregating over 4 million gross tonnes. In Great Britain, Norway’s military units were built up again within all the services. They took part in the naval campaigns in the Atlantic, in the combat following the invasion of continental Europe in 1944, and in the air combat over the UK and the Continent. Towards the end of the war, the Swedes permitted Norway to build up military units in Sweden. Some of these forces took part in the campaigns against the German enemies. This happened after a Soviet force had attacked and liberated a small area of Norway in northeast Finnmark, in Norway's far north. In occupied Norway, civilian resistance grew from year to year. Secret military forces were also assembled, and were viewed as a threat by the Germans.
Norway was occupied right up to the German capitulation of 1945. When the surrender came there were no fewer than 400,000 German troops in Norway, which at that time had a population of barely 4 million. The occupation led to German exploitation of the Norwegian economy, and the Nazi reign of terror included executions and mass exterminations, though on a somewhat lesser scale than in many other occupied countries.
As early as 8 May 1945, Norwegian troops from the Resistance Movement started to take over positions from the Nazis. Gradually, they were joined by Allied and Norwegian troops from Great Britain and Sweden. The transition from occupying to allied forces was smooth. The exiled government returned home from Britain, and on 7 June King Haakon sailed into the port of Oslo onboard a British naval vessel.
Norwegian survivors began to emerge from the German concentration camps. At the end of the war 92,000 Norwegians were abroad, 46,000 of whom were in Sweden. In addition to the German occupiers, there were 141,000 foreign nationals in Norway, most of them prisoners of war. Of these, 84,000 were Russians.
During the course of the war the Germans had commandeered 40 per cent of Norway's GDP. In addition to this came the ravages of the war itself. In Finnmark these were considerable. Large areas were destroyed as a result of the "scorched earth" policy the Germans pursued during their retreat. Other towns and settlements were destroyed by bombing or deliberate burning.
A total of 10,262 Norwegians lost their lives either during the war or while they were imprisoned. About 40,000 were incarcerated.