It must be remembered that preventive action in foreign territory is justified only in case of "an instant and overwhelming necessity for self-defense, leaving no choice of means, and no moment of deliberation" (The Caroline Case, Moore's Digest of International Law, II, 412). How widely the view was held in influential German circles that the Allies intended to occupy Norway cannot be determined with exactitude. Quisling asserted that the Allies would intervene in Norway with the tacit consent of the Norwegian Government. The German Legation at Oslo disagreed with this view, although the Naval Attache at that Legation shared it.

The War Diary of the German Naval Operations Staff for 13 January 1940 stated that the Chief of the Naval Operations Staff thought that the most favorable solution would be the maintenance of the neutrality of Norway, but he harbored the firm conviction that England intended to occupy Norway in the near future relying on the tacit agreement of the Norwegian Government.

The directive of Hitler issued on 1 March 1940 for the attack on Denmark and Norway stated that the operation "should prevent British encroachment on Scandinavia and the Baltic."

It is, however, to be remembered that the Defendant Raeder's memorandum of 3 October 1939 makes no reference to forestalling the Allies, but is based upon "the aim of improving our strategical and operational position."

The memorandum itself is headed "Gaining of Bases in Norway". The same observation applies mutatis mutandis to the memorandum of the Defendant Dönitz of 9 October 1939.

Furthermore, on 13 March the Defendant Jodl recorded in his diary:

"Führer does not give order yet for 'W' (Weser Exercise). He is still looking for an excuse." (Justification?)
On 14 March 1940 he again wrote: "Führer has not yet decided what reason to give for 'Weser Exercise"'. On 21 March 1940 he recorded the misgivings of Task Force XXI about the long interval between taking up readiness positions and the close of the diplomatic negotiations, and added:

"Führer rejects any earlier negotiations, as otherwise calls for help go/ out to England and America. If resistance is put up it must be ruthlessly broken."
On 2 April he records that all the preparations are completed; on 4 April the Naval Operational Order was issued; and on 9 April, the invasion was begun.

From all this it is clear that when the plans for an attack on Norway were being made, they were not made for the purpose of forestalling an imminent Allied landing, but, at the most, that they might prevent an Allied occupation at some future date.