The Case Yellow directive

On 9 October 1939, three days after his speech in the Reichstag in which he had offered Britain and France peace on the ruins of Poland, Adolf Hitler signed two documents of an entirely different tenor. The first was a lengthy memorandum on the conduct of the war in the west, the second a short “Directive No. 6 for the Conduct of the War”, addressed to the commanders-in-chief of the army, the navy and the air force. The directive ordered the preparation of an attack on the northern flank of the western front, through Luxembourg, Belgium and the Netherlands, “as soon and in as great strength as possible”. The last Polish soldiers had barely laid down their arms, and planning for the war against France was already under way.

It is usually said that on 9 October Germany issued the orders for Case Yellow (Fall Gelb) to prepare the invasion of Belgium, France, Luxembourg and the Netherlands. This is broadly accurate, with two reservations. The directive itself did not yet use the code name Fall Gelb (“Case Yellow”). The army high command gave it that name ten days later, in the first operational plan of 19 October. Nor was this yet a decision to attack the whole of France: the objective of the attack was northern France, and the directive said nothing about further operations.

Hitler’s decision

Hitler did not wait for the end of the September Campaign to turn west. As early as 27 September, the day Warsaw surrendered, he summoned the commanders-in-chief of the armed services to the Reich Chancellery and told them that he intended to strike in the west that very autumn, before France and Britain could grow stronger (the Phoney War). The generals heard this with disbelief. Preparations for Case White had taken six months, and now they were to prepare, in a few weeks, a campaign against the strongest land army in Europe, backed by the British.

In this situation the peace offer of 6 October was a propaganda exercise rather than a genuine proposal. Hitler knew that London and Paris would not recognise the partition of Poland, and at most hoped that their refusal would let him present the continuation of the war to the Germans as something forced on them from outside. In the same speech, moreover, he assured Belgium and the Netherlands of his friendship and of respect for their neutrality, as he had done in the guarantee to Belgium of 1937 and again in August 1939. Three days later he signed an order that tore up that neutrality. Belgium and the Netherlands had declared their neutrality on 3 September and observed it strictly, and their governments knew nothing of the German plans.

The memorandum of 9 October

Hitler drafted the memorandum, entitled “Memorandum and Guidelines on the Conduct of the War in the West”, himself over a few days. On 10 October he read it out in the Reich Chancellery to the Commander-in-Chief of the Army, Colonel General Walther von Brauchitsch, and his chief of staff, General Franz Halder. It set out his entire strategy. The aim of the war was to be a final military reckoning with the West – that is, the destruction of the strength and capacity of the Western powers to oppose the further development of the German people in Europe. Hitler no longer spoke of Danzig or the Corridor, but of a decision that would give Germany a free hand on the Continent.

The memorandum’s central argument was time. Hitler claimed that it was working in his opponents’ favour. No agreement could guarantee the Soviet Union’s neutrality for ever, even though after the Molotov–Ribbentrop Pact and the Boundary and Friendship Treaty of 28 September Moscow was well disposed for the time being. Italy would side with Germany only if it saw German victories. The United States might in time begin to support the West. France and Britain would rearm with every passing month, and the British would bring more divisions over to the Continent. Hitler was particularly worried about the Ruhr, the heart of German industry, which lay close to the Belgian and Dutch borders. If the Allies entered those countries, they could paralyse the German economy from their airfields. From this he drew the conclusion that the attack had to begin as soon as possible, if possible that autumn.

The memorandum also contained military guidance that reflected the experience of Poland. Hitler wrote that there must be no return to the positional warfare that had bled the armies white in 1914–1918. Armoured and motorised forces were to operate in concentrated masses, break through the front and not get bogged down in fighting for towns and built-up areas. The air force was to destroy the enemy air force and support the advance of the ground troops.

Directive No. 6

Directive No. 6, short and matter-of-fact, turned these ideas into orders. It began by stating that if it became evident in the near future that England, and under her influence France too, were not willing to end the war, Hitler was determined to go over to offensive action without further delay. Any delay, he wrote, would lead to the end of Belgian, and perhaps Dutch, neutrality to the Allies’ advantage, would increase the enemy’s military strength, would weaken the neutrals’ confidence in Germany’s final victory and would not encourage Italy to enter the war.

The attack was to be carried out on the northern flank of the western front, through the territory of Luxembourg, Belgium and the Netherlands. Its aim was to defeat as large a part of the French army and its allies as possible, and at the same time to seize as much territory as possible in the Netherlands, Belgium and northern France as a base for air and naval warfare against England and as a broad glacis protecting the Ruhr. The date was to depend on the readiness of the armoured and motorised units and on the weather. The Luftwaffe was to protect the ground forces from the Anglo-French air forces, support their attack and prevent the Allies from establishing air bases in Belgium and the Netherlands, while the Kriegsmarine was to support the operations of the other two services. Independently of the preparations for the attack, the forces were to be kept constantly ready, should the French and British enter Belgium, to advance at once as far as possible into Belgian territory and to occupy as much of the Netherlands as possible towards the west coast. Troop movements were to be camouflaged as precautions against an alleged Allied threat. Finally, Hitler demanded detailed plans and regular reports from the commanders-in-chief through the High Command of the Wehrmacht (OKW).

The directive was thus an order to attack three neutral states, none of which had given Germany any cause for war. The invasion of Belgium and the Netherlands was justified in advance by the Allies’ alleged intention to do the same. The prosecutors at Nuremberg later cited it as evidence of the planning of a war of aggression and of the breaking of guarantees that Hitler himself had given.

The first Case Yellow plan

The operational plan was drawn up by the army general staff at Zossen near Berlin, the headquarters of the Army High Command (OKH). On 19 October OKH issued its first “deployment instruction” under the code name Gelb. Its aim was formulated almost in the words of the directive: to defeat as large a part of the French and Allied armies as possible and to seize as much of the territory of the Netherlands, Belgium and northern France as possible as a base for the war against England and a glacis for the Ruhr. The main blow was to be delivered by Army Group B under Colonel General Fedor von Bock, concentrating three armies in central Belgium, north and south of Brussels. The armoured and motorised divisions were then to strike on the right wing towards Ghent and Bruges. The plan covered only the first phase of the campaign: it ended with the arrival at the northern border of France and said nothing about what would come next.

In this it resembled the Schlieffen Plan of 1914, though it was more modest, since it did not envisage encircling the French army. It satisfied no one, Hitler included. On 25 October Hitler summoned Brauchitsch and Halder and, according to the diary of the OKW’s chief of operations staff, General Alfred Jodl, said that he had originally wanted to attack with all his forces south of Liège, towards Reims and Amiens. After further talks he announced his decision on 28 October: the attack was to go both north and south of Liège, with a group of armoured divisions in each wing. On 29 October OKH issued the second version of the plan. Army Group B kept the main effort, while Colonel General Gerd von Rundstedt’s Army Group A was merely to cover its left flank. On 30 October, according to Jodl’s record, Hitler came up with a “new idea”: to send an armoured and a motorised division through Arlon towards Sedan. A day later Rundstedt’s chief of staff protested against the whole plan. He was Generalleutnant Erich von Manstein.

The generals’ resistance

To the generals an autumn offensive was madness. The campaign in Poland had been shorter than expected, but it had exposed the army’s weaknesses: shortages of ammunition and bombs, worn-out tanks and vehicles in need of repair, poorly trained reserve divisions, and infantry which, in the view of many commanders, was not a match for that of 1914. The French army was still regarded as the strongest in Europe, it was backed by the Maginot Line, and the British Expeditionary Force was taking up positions on the Belgian border. In autumn the days were short, and rain and mud could immobilise the tanks and ground the air force, on which the Wehrmacht relied most.

The commanders of all three army groups in the west were opposed. Colonel General Wilhelm von Leeb, commander of Army Group C, sent Brauchitsch a memorandum in mid-October arguing that an attack through neutral states would turn world opinion against Germany, would bring no decision and might end in a war of attrition. Bock and Rundstedt also believed that an autumn attack would not yield a decisive victory. Brauchitsch and Halder shared these fears. According to an entry in Halder’s diary of 14 October, they considered three possibilities: attack, waiting, or “fundamental changes”. These words are read as an allusion to removing Hitler.

The Zossen conspiracy

The order to attack in the west revived the conspirators of 1938, who had planned to overthrow Hitler during the Sudeten crisis and had been left without a pretext after the Munich Agreement. The centre of the preparations became the Abwehr, where Colonel Hans Oster had long kept in touch with opponents of the regime, together with its liaison officer at OKH, Lieutenant Colonel Helmuth Groscurth. A memorandum entitled “The Impending Disaster”, written in October by Groscurth, the diplomat Hasso von Etzdorf and Erich Kordt of the German Foreign Office, circulated among the officers. Its authors argued that protests and resignations would not stop Hitler and that he had to be removed “in good time”, before the attack in the west dragged Germany into catastrophe. The former Chief of the General Staff Ludwig Beck and the former Lord Mayor of Leipzig Carl Goerdeler urged that the army had its last chance to prevent a world war.

Halder wavered. According to Groscurth’s diary, on 1 November he confessed to him, with tears in his eyes, that for weeks he had been going to meetings with Hitler with a pistol in his pocket in order to shoot him if necessary. He could not bring himself to do it, however, and did not want to lead a coup without Brauchitsch. Meanwhile, on 22 October, Hitler set the start of the offensive for 12 November. The matter was settled by a meeting at the Reich Chancellery on 5 November, when Brauchitsch put the generals’ objections to Hitler. Hitler flew into a rage, accused the army of defeatism and threatened to stamp out “the spirit of Zossen”. Brauchitsch and Halder concluded that the conspiracy had been discovered. Halder had some of the documents burned, and preparations for a coup were abandoned. That same day Hitler confirmed the order to attack, but on 7 November, owing to bad weather, he postponed it for the first time.

Place in the war

Directive No. 6 opened a period that in the west was called the Phoney War, but which for the German staffs was a time of feverish planning. From then on the date of the attack was postponed about thirty times – 29 is the figure most often given – because of the weather, the state of the troops and disputes over the plan. On 31 October Army Group A sent OKH the first of Manstein’s memoranda, which called for the main effort to be shifted south, through the Ardennes. For the next three months OKH rejected the idea, even though Hitler himself was looking for similar solutions. On 10 January 1940 a German courier aircraft carrying documents of the Case Yellow plan made an emergency landing in Belgium (the Mechelen incident). In February Hitler adopted Manstein’s concept, and on 24 February 1940 OKH issued a new version of the plan, with the main thrust delivered by Army Group A through the Ardennes towards Sedan and on to the English Channel.

The attack began on 10 May 1940 and ended in the defeat of France within six weeks. Hitler claimed the victory as his own, and the generals who in the autumn had considered the offensive madness lost what remained of their authority with him. The Netherlands surrendered on 14 May, Belgium on 28 May, and Luxembourg was occupied in a single day. The first objective set out in the directive, the Channel coast as a base for the war against Britain, was achieved, but the British did not make peace. For Poland, whose government and rebuilt army were by then in France, the fall of its ally meant a second evacuation, this time to Britain. The directive of 9 October was the first order that turned the war over Poland into a war for mastery of Western Europe.