On the 15th, further intercepted signals ordering the submarines to disperse revealed that the Soviet–Finnish ceasefire had indeed upset the Allied plans. Interpretation of the signals indicated the operation was not cancelled, just put on hold with forty-eight to ninety-six hours’ notice. Oberst Warlimont concluded in a memorandum to Jodl that he believed the pretext for an Allied intervention in Norway had gone and that Operation Weserübung should be cancelled and the forces released. The SKL took a more conditional stance:
The consequence of the Finnish–Russian ceasefire for Germany’s warfare is as yet unclear. The Allied plans for an immediate landing in Norway . . . seem to have been deferred for the moment. The SKL believes England’s strategic goals in the north have not changed and the planned action will be initiated when another favourable occasion has been found.102
At the Führer conference on 26 March, intelligence was presented showing how close an Allied intervention in Norway had been when the Finnish–Russian ceasefire was announced. Raeder added that even if the imminent danger of such an operation had been reduced, the ultimate objective of the Allies to sever the iron-ore supplies to Germany remained and an intensified effort against German merchant traffic in neutral waters was to be expected. Sooner or later, Allied plans for an intervention in Norway would re-emerge and Germany would have to carry out Weserübung. The operation had originated from the premise that Germany could not accept British control of Norwegian territory and that only a pre-emptive occupation could avert that. Therefore, Raeder suggested, Weserübung should be initiated in the next new-moon period and no later than 15 April. Everything was ready and the dark nights needed to cover the transit would soon become too short, increasing the overall risk to the operation. Virtually all operational U-boats had been deployed along the Norwegian coast or in the North Sea during March and would start running low on fuel and provisions in mid-April, thus closing the current window of opportunity. Sooner or later it would also be noted in London that other naval operations had been suspended. Earlier in the day, Raeder said, he had met with Hagelin and learned that the Norwegian Admiral Staff expected British naval forces to take control of the Norwegian Leads soon in a ‘staged provocation’, followed by seizure of naval and air bases in southern Norway. Hagelin believed that the Norwegian government would, at the most, offer only symbolic opposition. Careful as always, Raeder added that in spite of intelligence reports to the contrary, he personally was not sure an Allied intervention in Norway was imminent.103 Hitler concluded that it was not to be expected that the Allies had abandoned their strategy in the north; threats of a German attack in France could trigger an Allied intervention in Norway. Hence, a preliminary date for Weserübung was set for between 8 and 10 April. The SKL, on Raeder’s instruction, issued orders that all ships should remain on stand-by and arrangements for embarkation of troops and equipment continued until further notice – as should all security measures.104
In the evening of 26 March, Kapitänleutnant Wolf-Harro Stiebler lost his bearings during a snowstorm in the Skagerrak and ran his boat U21 firmly onto Oddskjæret, one of the southernmost rocks of the Norwegian coast, well inside territorial waters. The Norwegian government wished to make a stand and decided to intern the boat and its crew. A minor diplomatic crisis ensued, but Germany could not afford a disturbance at that moment and Kapitänleutnant Stiebler and U21 were sacrificed for the greater cause. He was ordered to escape if possible and that was it.105
The news from the Supreme War Council meeting on 28 March was taken as evidence that it had been correct to assume that Allied interest in Norway had not lessened. In the evening of the 28th, the Naval Chief of Staff Fregattenkapitän Schulte-Mönting told the Swedish naval attaché in Berlin Kommendörkapten Anders Forshell over dinner that the political and military development in the north was ‘highly disturbing’. Germany feared Allied interventions on the Norwegian coast, in particular against Narvik, and with the Russians now having concluded the campaign in Finland, there was no knowing what they would do next. An ‘Anglo-Russian race’ for Narvik could not be accepted, and Germany would have to initiate countermeasures should this appear to become reality. A pre-emptive strike was far better than a belated reaction. The challenge according to Schulte-Mönting was where to strike and when.106
The plans for Operation Weserübung were formally approved by Hitler on the afternoon of 1 April after a five-hour, detailed review of the operation in the Reichskanzlei, starting at 13:00 with ‘breakfast’. Von Falkenhorst and all senior navy, army and Luftwaffe commanders involved in the operation were present and Hitler talked to each one of the officers. According to von Falkenhorst, ‘He cross-examined every man, who had to explain very precisely the nature of his task. He even discussed with the ship commanders whether they would land their men on the right or on the left side of a given objective. He left nothing to chance; it was his idea, it was his plan, it was his war.’ Satisfied with what he heard, the Führer ended the meeting with a commanding appeal, underlining the importance of the operation for the conduct of the war.107
The following day, 2 April, Hitler asked for assurance by Raeder, Göring, Keitel and von Falkenhorst that all preparations were completed and neither ice nor weather could create adverse conditions. This they all confirmed. Hitler then asked Oberst Erich Buschenhagen, Chief of Staff for Group XXI, as the corps had temporarily been renamed, what would be the latest possible date to cancel the operation. The baffled Buschenhagen, who had worked day and night for five weeks preparing the operation, had not given this much thought, but after some deliberation answered ‘Wesertag minus five’. The operation could be cancelled or postponed without risk until five days before the designated day of the invasion; after that, wheels would be rolling and the number of involved personnel with knowledge of what was happening would rise sharply.108 Hitler gave the answer some consideration and decided the invasion should commence at 05:15, German time, on 9 April. The first supply ships would be at sea within less than forty-eight hours. At 19:17 on 2 April a signal was sent from the SKL to Groups East and West, C-in-C U-boats and C-in-C Fleet: ‘Wesertag ist der 9. April.’109 A note was made in the SKL War Diary:
With the order from the Führer . . ., Weserübung has been initiated, commencing one of the boldest operations in the history of modern warfare. Its implementation has become necessary in order to defend vital German interests and supply of raw materials, which the enemy is attempting to sever . . . The outcome of the venture will to a large degree depend on the quality and the readiness of the naval forces as well as the determination of the individual officers in command. The landing operation will predominantly take place in an area where England rather than Germany has naval supremacy. Surprising the enemy . . . is important for success, and will depend on the extent to which, in the coming days, secrecy can be maintained . . .
And on 5 April:
The at times limited operational options of the German sea and air forces will improve significantly through an occupation of southern Norway. Germany now has the capacity to implement such an incursion swiftly. The basis for the operation will obviously be the loss of Norwegian neutrality to England and the total inability of the Norwegians to resist this loss.110
Acting Commander-in-Chief for Group West Generaladmiral Rolf Carls wrote in his war diary on 6 April as he was handing the command of the group back to Generaladmiral Alfred Saalwächter, returning to his own command in Group East:
The significance of this operation is not only to secure the ore supplies and to sever British trade with Norway, but to include the whole of Scandinavia in the German power-sphere . . . The British have to a large extent influenced the timing of the operation. A massive attempt from their side to forestall our seizing of the Norwegian harbours is to be expected . . . The risks associated with this task for the deployed surface units of the navy are well known to the SKL as well as to the Führer; [Raeder] has seen to that, in the same way as all group commanders have been made aware that the success of this operation, contrary to conventional, operative considerations, is based on secrecy, surprise, lack of Norwegian opposition and ruthless use of force to overcome all difficulties.111
The multiple set of motives behind Operation Weserübung is evident.