The main strategic reason for Germany to invade Norway was to seize the port of Narvik and guarantee the delivery of iron ore needed for German steel production.

The abandonment of the planned landings put immense French pressure on Neville Chamberlain's British government, and eventually led to the Allies laying mines off the Norwegian coast on 8 April.

[17] Altmark had spent the prior months as a fleet oiler turned prison ship for the German cruiser Admiral Graf Spee while the latter was acting as a commerce raider in the South Atlantic.

[1][16][17] With the end of the Winter War, the Allies determined that any occupation of Norway or Sweden would likely do more harm than good, possibly driving the neutral countries into an alliance with Germany.

This was soon changed to a plan involving the mining of Norwegian waters to stop iron ore shipments from Narvik and provoke Germany into attacking Norway, where it could be defeated by the Royal Navy.

[18] It was agreed to use Churchill's naval mining plan, Operation Wilfred, designed to remove the sanctuary of Norway's coastal waterways and force transport ships into international waters, where the Royal Navy could engage and destroy them.

Another matter that caused additional reworking of the plan was Fall Gelb, the proposed invasion of northern France and the Low Countries, which would require the bulk of German forces.

Although the weather did make reconnaissance difficult, the two German groups were discovered 170 km (110 mi) south of the Naze (the southernmost part of Norway) slightly after 08:00 by Royal Air Force (RAF) patrols and reported as one cruiser and six destroyers.

In response, the Admiralty ordered Renown and her single destroyer escort (the other two had gone to friendly ports for fuel), to abandon her post at the Vestfjord and head to Glowworm's last known location.

On the morning of 8 April, the Polish submarine ORP Orzeł sank the clandestine German troop transport ship Rio de Janeiro off the southern Norwegian port of Lillesand.

The Danish army was small, ill-prepared and used obsolete equipment, but resisted in several parts of the country; most importantly, the Royal Guards located at Amalienborg Palace in Copenhagen, and forces in the vicinity of Haderslev in South Jutland.

RAF reconnaissance soon reported stronger opposition than anticipated, and this, along with the possibility that the Germans might be controlling the shore defences, caused them to recall the force and instead use the aircraft carrier HMS Furious to launch torpedo bombers at the enemy ships.

On 10 April, the Fleet Air Arm made a long-range attack from their base at RNAS Hatston (also called HMS Sparrowhawk) in the Orkney Islands against German warships in Bergen harbour.

Admiral Hipper, however, had already managed to escape through the watch set up outside the port and was on her way back to Germany when the attack was launched; none of the remaining German destroyers or support ships were hit in the assault.

[49] On 11 April, after receiving reinforcements in Oslo, General Falkenhorst's offensive began; its goal was to link up Germany's scattered forces before the Norwegians could effectively mobilize or any major Allied intervention could take place.

Dissension among the various branches was strong though, as the British Army, after conferring with Otto Ruge, wanted to assault Trondheim in Central Norway while Churchill insisted on reclaiming Narvik.

[50] After the appointment of Ruge as Commanding General on 10 April, the Norwegian strategy was to fight delaying actions against the Germans advancing northwards from Oslo to link up with the invasion forces at Trondheim.

Several of the units facing the German advance were led by officers especially selected by Ruge to replace commanders who had failed to show sufficient initiative and aggression in the early days of the campaign.

After several days of confusion and episodes of panic among the Norwegian troops, despite the complete absence of fighting, the 2,000 men of the defending 3rd Division in Setesdal surrendered unconditionally on 15 April.

[1] To block the expected allied landings the Oberkommando der Wehrmacht ordered a Fallschirmjäger company to make a combat drop on the railway junction of Dombås in the north of the Gudbrandsdal valley.

[55] In the waning hours of 14 April, Mauriceforce, composed primarily of the British 146th Infantry Brigade and commanded by Major-General Adrian Carton de Wiart made their initial landings at the Norwegian port town of Namsos.

On 20 April German aircraft bombed Namsos, destroying most of the houses in the town centre, and large portions of the supply storage for allied troops, leaving de Wiart without a base.

[1][79] Organized Norwegian military resistance in the central and southern parts of Norway ceased on 5 May, with the capitulation of the forces fighting at Hegra in Sør-Trøndelag and at Vinjesvingen in Telemark.

[16] The failure of the central campaign is considered one of the direct causes of the Norway Debate, which resulted in the resignation of British Prime Minister Neville Chamberlain and the appointment of Winston Churchill to the office.

The Norwegian counter-offensive against the Germans at Narvik was hampered by Fleischer's decision to retain significant forces in Eastern Finnmark to guard against a possible Soviet attack in the far north.

[88] On 15 April, the Allies scored a significant victory when the Royal Navy destroyers Brazen and Fearless, which were escorting the troop-carrying Convoy NP1, forced the German U-boat U-49 to surface and scuttle in the Vågsfjorden.

[94] As the Germans advanced northward from a railhead at Mosjøen, the garrison of Mo i Rana (a mixed force based on the 1st Scots Guards) withdrew on 18 May, too precipitately in Gubbins's opinion.

The brigade withdrew under heavy pressure across Skjerstad Fjord on 25 May, covered by a rearguard from the 1st Irish Guards and several of the Independent Companies under Lieutenant Colonel Hugh Stockwell.

After a meeting on 7 June at which the decision to carry on the fight abroad was made, King Haakon VII, Crown Prince Olav and the Norwegian cabinet left Norway on the British cruiser Devonshire and went into exile in the United Kingdom.

The ranks of the Navy and Air Force were swollen by a steady trickle of refugees making their way out of occupied Norway, and their equipment brought up to standard by British and American aircraft and ships.