As mentioned above, things had changed in April 1940: on April 9, 1940, Germany invaded Denmark and Norway in Operation Weserübung. The military facts:
Presented with a diplomatic note of “surrender or be destroyed”, the Danish government capitulated in the early hours of April 9, 1940, after German para-troopers had already begun to seize key positions and airfield in the country. Likewise, the Luftwaffe took out most of the small air service arm of the Danish armed forces.
Confronted with the imminent threat of the Luftwaffe bombing Copenhagen and being hopelessly outnumbered, the Danish government surrendered.
Unlike Denmark, Norway decided to fight the invasion as good as possible. Although the German landing operations on April 9, 1940, succeeded in general, the resistance of Norwegian forces was unbroken.
The Norwegian forces were backed by Great Britain, France and Polish Forces which now recognized the true nature of the German operation and mounted a counter-attack. Allied forces landed in central Norway on April 12, 1940. Their attempt was in vain – the allied forces had to retreat from central Norway and withdrew on May 2, 1940.
A second allied landing took place in the north, around Narvik. They landed on April 14, 1940 and recaptured the city on May 28, 1940. But once more, the success was short-lived: the situation in the Low Countries and France, where the Wehrmacht had started the War in the West on May 10, 1940, had shifted the attention of the Allied and made Norway a less important objective than before.
The evacuation of the Allied expeditionary force was finished on June 8, 1940 – with the troops, the Norwegian King Haakon VII and the Crown Prince, Olav, as well as the Norwegian cabinet left Norway and went into exile in the United Kingdom. The Norwegian forces surrendered June 10, 1940.
From an academic point of view, there could possibly be a discussion as to the reasons for Operation Weserübung. Germany certainly had an interest in secured access to the Swedish iron ore – and that was, to a large extent – shipped through the port of Narvik.
But iron ore was just one side of things – the other certainly was access to the North Atlantic. Despite Norway providing ports to the Kriegsmarine if captured, it can also be assumed that Great Britain would – if they themselves would have found a way into Norwegian waters and ports – effectively have sealed of German access to the high seas and made marine warfare almost impossible for Germany. And the plans for Operation Wilfred and Plan R 4 show that it had indeed been a possible scenario…