Hitler postpones the attack in the West

On 16 January 1940, at around 7 p.m., Adolf Hitler agreed to call off the offensive against the Netherlands, Belgium and Luxembourg that had been set for 17 January. This time he did not merely move the date back by a few days, as he had done many times since November, but postponed the offensive indefinitely – in practice until the spring. At the same time he declared that the whole operation had to be built “on a new basis”, so as to ensure secrecy and surprise. The decision closed the first, autumn and winter, phase of planning for the campaign in the West and opened the way to the change of plan that in May 1940 sealed the defeat of France.

Many chronologies state that on 16 January captured documents revealed Hitler’s plans for an invasion of Scandinavia and the postponement of the invasion of France and the Low Countries until the spring, when the weather would be more favourable. The date and the decision to postpone the attack are correct, but the rest of the sentence conflates several different matters. The documents that had fallen into Belgian hands six days earlier in the Mechelen incident concerned only the offensive in the West – more precisely, the part to be played by the air force and airborne troops in the attack through Belgium and the Netherlands. They contained not a word about Scandinavia. Nor did they “reveal” the postponement of the attack: that was decided by Hitler himself, after their loss, and no one on the Allied side knew of the decision at the time. In Berlin the plans for Norway were a separate thread, developed during the same weeks in the High Command of the Wehrmacht (as described below).

A date never once kept

Hitler had wanted to strike in the West as early as the autumn of 1939. Directive No. 6 of 9 October ordered an offensive to be prepared “as early as possible”, and on 22 October he set its start for 12 November. The generals, led by the Commander-in-Chief of the Army, Colonel General Walther von Brauchitsch, and the Chief of the General Staff, General Franz Halder, regarded an autumn offensive as a risk beyond the strength of an army that had only just emerged from the September Campaign. After a stormy interview with Brauchitsch on 5 November Hitler upheld the order, but on 7 November, because of bad weather, he postponed the date for the first time, a few days before Elser’s assassination attempt in Munich.

From then on the mechanism was always the same. The date of the attack, called “A-Day” in the orders, was announced several days in advance, because the troops needed time to move from their billeting areas to their start lines. A few days beforehand Hitler, on the basis of the meteorologists’ forecasts, either confirmed it or postponed it, usually by a few days or a week. The documents presented at Nuremberg included eighteen such orders of the High Command of the Wehrmacht (OKW), signed by Colonel General Wilhelm Keitel or by the chief of the operations staff, Generalmajor Alfred Jodl, between 7 November 1939 and 9 May 1940. In all, counting decisions not recorded in separate orders, the date of the offensive was postponed 29 times according to the most commonly cited reckonings. In December Hitler agreed to a Christmas break and leave for the troops, and put off the decision on the date until the end of the year.

The reasons were not only meteorological. The offensive relied on the air force, which was to destroy the enemy’s air forces and support the armoured divisions, and for that it needed several consecutive days of good visibility. In the autumn the days were short, and rain turned roads and fields to mud. On top of the weather came the state of the troops, still being brought back up to strength after the fighting in Poland, and an unresolved dispute over the plan. On 19 and 29 October the OKH (the Army High Command) issued two versions of the Case Yellow (Fall Gelb) plan, with the main blow delivered by Army Group B in central Belgium, while the staff of Army Group A in Koblenz, through the mouth of Generalleutnant Erich von Manstein, had been arguing since 31 October that such a blow would push the Allies back towards the Somme but would not destroy them. Brauchitsch kept Manstein’s successive memoranda to himself; the last was written on 12 January 1940.

From 10 to 16 January

At the beginning of January winter set in with a hard frost, which in dry weather gave the air force good visibility and the tanks firm ground. On 10 January Hitler decided that the time had come and set the offensive for 17 January, a quarter of an hour before sunrise. That same day a light Messerschmitt Bf 108 aircraft, in which Major Erich Hoenmanns was flying with Major Helmuth Reinberger, a staff officer of the German airborne forces, lost its way in fog and made a forced landing near Maasmechelen in Belgian Limburg. Reinberger was carrying documents concerning the role of the air force and the airborne landings in the offensive. He tried to burn them, but most fell into Belgian hands in a legible state.

The news reached Berlin late on the evening of 10 January. Hitler flew into a rage. On 12 January (some sources say as early as 11 January) the commander of Air Fleet 2, in whose area the aircraft had taken off, General Hellmuth Felmy, and his chief of staff, Colonel Josef Kammhuber, were dismissed. Command of the air fleet was taken over by General Albert Kesselring. The same day Hitler signed the so-called Basic Order No. 1 on secrecy: no one was to know more about secret matters than his task required, or to learn of them earlier than was necessary. On 12 January Jodl noted in his diary that if the enemy had all the documents, the situation was catastrophic. The following day, after the German air attaché in Brussels had spoken with both airmen, he calmed down, writing that the briefcase had “certainly” been burned. The Belgians had deliberately allowed this meeting to take place, in the hope that the Germans would believe the documents had been destroyed and would not change their plan.

The Belgians and the Dutch, meanwhile, were taking action. The government in Brussels passed the contents of the documents to the French and the British, and on 14 January, after further warnings of German preparations, placed the army on the highest state of readiness and recalled soldiers from leave. The Dutch stopped all leave. The French Commander-in-Chief, General Maurice Gamelin, counting on the Belgians to ask for help at any moment and on being able to carry out the Dyle Plan, moved Allied forces up to the Belgian frontier during the night of 14/15 January. The Belgians even began removing the barriers on the border with France, but on the morning of 15 January they stopped. The Belgian government had no intention of letting foreign troops in before a German attack, and the disappointed Allies withdrew to their positions. On the British side there was no shortage of suspicion that the whole affair was a German provocation and that the documents had been planted deliberately. Historians who have studied the matter have not confirmed this theory.

In Berlin the Belgian alarm and the French troop movements did not go unnoticed. The weather changed too. The frost held, but heavy snowfalls came, and the forecasts offered no hope of several fine days in a row. On 13 January, in view of poor forecasts, the final decision on the date was put off by a few days, and by 15 January the roads were in such a bad state that Jodl advised Hitler to abandon the attack for the time being. Hitler hesitated until the evening of 16 January and then accepted this advice. The winter of 1939/1940 was one of the harshest in Europe in the twentieth century and would indeed have paralysed the movement of armoured and motorised columns on Belgium’s narrow roads.

A compromise and a “new basis”

The decision of 16 January was therefore a compromise between the weather and the consequences of Mechelen. Hitler did not know how much the Belgians had actually read, but he had to reckon with the possibility that the plan of attack was known to the enemy, and the alarm in Belgium and the Netherlands had robbed the attack of surprise. Rather than plunge into the snow against a prepared enemy, he preferred to wait. According to Jodl’s note of 16 January, he decided that the whole operation had to be built on a new basis in order to ensure secrecy and surprise. Above all this meant a different deployment of the troops: the mobile units were to be positioned so that they could attack almost straight from the march, without the long and conspicuous regroupings that since November had time and again betrayed German intentions.

Postponing the offensive until the spring also provided time that had so far been lacking. The generals, who had opposed the offensive since the autumn, for the first time since November were not obliged every few days to prepare for an attack that was then called off at the last minute. The OKH set about reworking the plan. At the end of January it issued a third version, in which Colonel General Gerd von Rundstedt’s Army Group A received more forces, but the main blow was still to be struck by Colonel General Fedor von Bock’s Army Group B in central Belgium. Halder, who had been rejecting Manstein’s ideas since the autumn, still had no intention of shifting the weight of the offensive to the Ardennes. On 27 January Manstein was appointed commander of a corps being formed in Stettin (Szczecin), far from the Western Front, which in practice removed him from the planning.

Historians still argue over whether the Mechelen incident caused the change of plan. Some, Karl-Heinz Frieser among them, believe that the loss of the documents merely hastened a change that would have come anyway, since Hitler himself had already been looking in the autumn for a thrust through the Ardennes towards Sedan, and the first plan satisfied no one. What the Germans saw in mid-January may have mattered more than the documents themselves: the readiness of the Allies to advance deep into Belgium at the first signal. Such a move was exactly what Manstein’s idea depended on.

Scandinavia: a separate thread

The misleading reference to Scandinavia has some basis in the calendar, because the two threads ran in the same weeks. Since October the Commander-in-Chief of the Navy, Grand Admiral Erich Raeder, had been urging Hitler that Germany must forestall the British in Norway. In December, after meetings with the Norwegian far-right leader Vidkun Quisling, Hitler instructed the OKW to examine the possibility of an operation, and in January a preliminary study, called “Studie Nord”, was produced there. The Allies for their part were considering sending troops to Scandinavia under the pretext of helping Finland in its war with the USSR, which would also allow them to cut Germany off from Swedish iron ore.

The Mechelen documents, however, had nothing to do with this, and the decision of 16 January did not mean a shift of attention from the West to the North. Postponing the offensive until the spring did, however, give Hitler several months in which he could deal with Norway first. Eleven days later, on 27 January, Keitel ordered a separate staff to be set up within the OKW to plan an operation against Norway, which was given the code name “Weserübung”.

Place in the war

Postponing the attack until the spring proved to be one of the most important decisions of the first year of the war, although when it was taken it looked like just another change of date. On 2 February Hitler’s chief adjutant, Colonel Rudolf Schmundt, briefed in Koblenz by officers of the Army Group A staff, put Manstein’s concept to Hitler, and the OKH war games in February showed that an advance on Sedan required far greater forces than had been assumed. On 17 February Manstein presented his plan to Hitler at the Reich Chancellery, and on 24 February the OKH issued the fourth version of Case Yellow, with the main blow delivered by Army Group A through the Ardennes. Before the offensive in the West began, Germany attacked Denmark and Norway on 9 April.

On 10 May 1940 the Wehrmacht struck at the Netherlands, Belgium and Luxembourg. The Allies, following the Dyle Plan, extended in March to include an advance into the Netherlands, moved deep into Belgium, while the German armoured divisions passed through the Ardennes, forced the Meuse at Sedan on 13 May and reached the English Channel on 20 May. France capitulated after six weeks. Had Hitler attacked in January according to the original plan, against a prepared enemy and in the snow, the battle in Belgium might have ended as Manstein had predicted: with the front halted on the Somme and a long war of position. The winter, the lost documents and the decision of 16 January meant that Germany struck only in the spring – and according to a plan the Allies did not expect.