On the morning of 11 April 1940, in an attempt to wipe out Norway's unyielding king and government, Luftwaffe bombers attacked Nybergsund, destroying the small town where the Government was staying. Neutral Sweden was only 16 miles away, but the Swedish government decided it would "detain and incarcerate" King Haakon if he crossed their border (which Haakon never forgave). The Norwegian king and his ministers took refuge in the snow-covered woods and escaped harm, continuing farther north through the mountains toward Molde on Norway's west coast. As the British forces in the area lost ground under Luftwaffe bombardment, the King and his party were taken aboard the British cruiser HMS Glasgow at Molde and conveyed a further 1,000 kilometres (620 mi) north to Tromsø, where a provisional capital was established on 1 May. Haakon and Crown Prince Olav took up residence in a forest cabin in Målselvdalen valley in inner Troms County, where they would stay until evacuation to the United Kingdom. While residing in Tromsø, the two were protected by local rifle association members armed with the ubiquitous Krag-Jørgensen rifle.
The Allies had a fairly secure hold over northern Norway until late May. The situation was dramatically altered, however, by their deteriorating situation in the Battle of France. With the Germans rapidly overrunning France, the Allied high command decided that the forces in northern Norway should be withdrawn. The Royal Family and Norwegian Government were evacuated from Tromsø on 7 June aboard HMS Devonshire with a total of 461 passengers. This evacuation became extremely costly for the Royal Navy when the German warships Scharnhorst and Gneisenau attacked and sank the nearby aircraft carrier HMS Glorious with its escorting destroyers HMS Acasta and HMS Ardent. Devonshire did not rebroadcast the enemy sighting report made by Glorious as she could not disclose her position by breaking radio silence. No other British ship received the sighting report, and 1,519 British officers and men and three warships were lost. Devonshire arrived safely in London and King Haakon and his Cabinet set up a Norwegian government in exile in the British capital.
Initially, King Haakon and Crown Prince Olav were guests at Buckingham Palace, but at the start of the London Blitz in September 1940, they moved to Bowdown House in Berkshire. The construction of the adjacent RAF Greenham Common airfield in March 1942 prompted another move to Foliejon Park in Winkfield, near Windsor, in Berkshire, where they remained until the liberation of Norway. The King's official residence was the Norwegian Legation at 10 Palace Green, Kensington, which became the seat of the Norwegian government in exile. Here Haakon attended weekly Cabinet meetings and worked on the speeches which were regularly broadcast by radio to Norway by the BBC World Service. These broadcasts helped to cement Haakon's position as an important national symbol to the Norwegian resistance. Many broadcasts were made from Saint Olav's Norwegian Church in Rotherhithe, where the Royal Family were regular worshippers. Famously, one of the broadcasts went badly wrong when instead of the expected fanfare, the sound library delivered the sound of a funfair. Luckily, King Haakon found the mix-up funny and stifling a giggle, pronounced to the Norwegian people "Roll up, Roll up, all the fun of the fair" and managed to incorporate the fair reference into the speech he was intending to give.
Meanwhile, Hitler had appointed Josef Terboven as Reichskommissar for Norway. On Hitler's orders, Terboven attempted to coerce the Storting to depose the King; the Storting declined, citing constitutional principles. A subsequent ultimatum was made by the Germans, threatening to intern all Norwegians of military age in German concentration camps. With this threat looming, the Storting's representatives in Oslo wrote to their monarch on 27 June, asking him to abdicate. The King declined, politely replying that the Storting was acting under duress. The King gave his answer on 3 July, and proclaimed it on BBC radio on 8 July.
After one further German attempt in September to force the Storting to depose Haakon failed, Terboven finally decreed that the Royal Family had "forfeited their right to return" and dissolved the democratic political parties.
During Norway's five years under German control, many Norwegians surreptitiously wore clothing or jewellery made from coins bearing Haakon's "H7" monogram as symbols of resistance to the German occupation and of solidarity with their exiled King and Government, just as many people in Denmark wore his brother's monogram on a pin. The King's monogram was also painted and otherwise reproduced on various surfaces as a show of resistance to the occupation.
After the end of the war, Haakon and the Norwegian Royal Family returned to Norway aboard the cruiser HMS Norfolk, arriving with the First Cruiser Squadron to cheering crowds in Oslo on 7 June 1945, exactly five years after they had been evacuated from Tromsø.