In October 1939, the chief of the Kriegsmarine, Grand-Admiral Erich Raeder, discussed with Adolf Hitler the danger posed by potential Allied bases in Norway and the possibility of Germany pre-emptively seizing those location.

The Kriegsmarine argued that a German occupation of Norway would allow control of the nearby seas and serve as a platform for staging submarine operations against the Allies.

Though later implemented, Operation Wilfred was initially rejected by Neville Chamberlain and Lord Halifax for fear of an adverse reaction among neutral nations such as the United States.

Planning for the expedition continued, but the justification for it was removed after the Moscow Peace Treaty between Finland and the Soviet Union had been signed in March 1940 and ended the Winter War.

Convinced of the threat posed by the Allies to the iron ore supply, Hitler ordered the Oberkommando der Wehrmacht to begin preliminary planning for an invasion of Norway.

It decided upon two key factors: surprise was essential to reduce the threat of Norwegian resistance (and Allied intervention), and faster German warships, rather than comparatively slow merchant ships, should be used as troop transports.

The target objectives of the force were the Norwegian capital, Oslo, and other population centres: Bergen, Narvik, Tromsø, Trondheim, Kristiansand and Stavanger.

Hitler regarded the incident as a clear sign that the Allies were also willing to violate Norwegian neutrality, which made him become even more strongly committed to invading Norway.

On 5 April 1940, the long-planned Operation Wilfred was put into action, and a Royal Navy squadron led by the battlecruiser HMS Renown left Scapa Flow to mine Norwegian waters.

Given Denmark's position on the Baltic Sea, the country was also crucial for the control of naval and shipping access to major German and Soviet harbours.

At 04:00 on 9 April 1940, the German ambassador to Denmark, Cecil von Renthe-Fink, called the Danish Foreign Minister Peter Munch and requested a meeting with him.

When the two men met 20 minutes later, Renthe-Fink declared that German troops were then moving in to occupy Denmark to protect the country from Anglo-French attacks.

[8] At 04:20 local time, a reinforced battalion of German infantrymen from the 308th Regiment landed in Copenhagen harbour from the minelayer Hansestadt Danzig, quickly capturing the Danish garrison at the Citadel without encountering resistance.

The first German attack on Amalienborg was repulsed, giving Christian X and his ministers time to confer with the Danish Army chief General Prior.

At 05:25, two squadrons of German Messerschmitt Bf 110s attacked Værløse airfield on Zealand and neutralised the Danish Army Air Service by strafing.

[9][page needed] Faced with the explicit threat of the Luftwaffe bombing the civilian population of Copenhagen, and with only General Prior in favour of fighting on, King Christian and the entire Danish government capitulated at approximately 06:00, in exchange for retaining political independence in domestic matters.

[12] Norway was important to Germany for two primary reasons: as a base for naval units, including U-boats, to weaken Allied shipping in the North Atlantic, and to secure shipments of iron ore from Sweden through the port of Narvik.

The invasion of Norway was given to the XXI Army Corps under General Nikolaus von Falkenhorst and consisted of the following main units: The initial invasion force was transported in several groups by ships of the Kriegsmarine:[13] Shortly after noon on 8 April, the clandestine German troopship SS Rio de Janeiro was sunk off Lillesand by the Polish submarine ORP Orzeł, part of the Royal Navy's 2nd Submarine Flotilla.

Within two hours, the badly damaged ship, unable to manoeuvre in the narrow fjord from multiple artillery and torpedo hits, sank with very heavy loss of life totalling 600–1,000 men.

The threat from the fortress (and the mistaken belief that mines had contributed to the sinking) delayed the rest of the naval invasion group long enough for the Royal Family, the Cabinet and members of Parliament to be evacuated, along with the national treasury.

At 8:30 pm the Norwegian destroyer Æger was attacked and sunk outside Stavanger[15] by ten Junkers Ju 88 bombers, after it sank the German cargo ship MS Roda.

In land battles at Narvik, Norwegian and Allied forces under General Carl Gustav Fleischer achieved the first major tactical victory against the Wehrmacht in WWII.

King Haakon VII, Crown Prince Olav, and the Cabinet Nygaardsvold left from Tromsø 7 June aboard the British cruiser HMS Devonshire to represent Norway in exile.

However, it was determined that Germany had discussed invasion plans as early as 3 October 1939 in a memo from Admiral Raeder to Alfred Rosenberg whose subject was "gaining bases in Norway".

[c] Two diary entries by Alfred Jodl dated 13 and 14 March did not indicate any high-level awareness of the Allied plan but also that Hitler was actively considering putting Weserübung into operation.

The plan was to provoke a German reaction by laying mines in Norwegian waters, and once Germany showed signs of taking action, UK troops would occupy Narvik, Trondheim, and Bergen and launch a raid on Stavanger to destroy Sola airfield.

[22] The International Military Tribunal at Nuremberg determined that no Allied invasion was imminent and so rejected the German argument that Germany was entitled to attack Norway.