Although Brauchitsch and Halder strongly opposed Manstein's suggestion, arguing that his so-called secret passage was a wild hypothesis that would expose the elite of German panzer forces to a flank attack by the French and possibly lead to the annihilation of the entire army. But under pressure from Hitler, the two army chiefs succumbed. As a result, the Chief of the General Staff of the Army, Halder, was ordered to reformulate the battle plan on the basis of Manstein's proposal.

On February 22, 1940, Hitler approved a new battle plan that was broadly identical to that envisioned by Manstein. The German General Staff replaced this plan with Operation Scythe. According to Heinz Brown, then commander of the 19th Panzer Corps? William? With the exception of Hitler, Manstein, and himself, almost no one else had confidence in the plan, Guderian said.

On 10 January 1940, a German Messerschmitt Bf108 was forced to land in Masmechelen, north of Maastricht, Belgium (the so-called "Mechelen Incident"). The passenger on the plane was Helmao, a key member of the Luftwaffe? Reinberger, who carries an up-to-date copy of the "Yellow Plan No. 2". Reinberger was unable to destroy the document, which soon fell into the hands of Belgian intelligence agencies.

It is often argued that this event was the reason for the major revisions planned by the German army, but this is not true; In fact, on 30 January, the military operation was re-designated as "Yellow Plan No. 3", which is largely in line with the previous version. On 27 January, Manstein was relieved of his post as Chief of the General Staff of Army Group A and transferred to the rank of corps commander in Prussia, where he began his command at Stettin on 9 February.

This move was made by Halder in order to eliminate Manstein's influence. Manstein's enraged subordinates presented his plan to Hitler's attention, which he obtained on 2 February. Manstein was invited to explain his proposal to the Führer personally in Berlin on 17 February. Hitler was impressed by the plan. The next day, he ordered to follow the von ? Manstein's conception changes the plan. These ideas appealed to Hitler primarily because they offered some hope of a real cheap victory.

Hitler ordered Franz? Halder changed plans again, von? Manstein did not intervene further. Halder agreed to transfer the main forces, the so-called "tactical breakthrough forces", to the south. Feng? Manstein's plan did not have much support (from a defensive point of view), because the Ardennes region was densely forested and had only a poor road system, which were unreliable as invasion roads. But there must therefore be an element of surprise that would be crucial to the Allies' response to the plan originally envisioned, in which the main elite forces of France and Britain would advance north to defend Belgium.

To help ensure that in this case, German Army Group B was to attack Belgium and the Netherlands, giving the impression that they were the main force of the German army, in order to lure the Allies east into the intended encirclement and pin them down. To do this, 3 of the existing 10 armored divisions were still assigned to Army Group B.

However, Halder had no intention of deviating from the established principle and allowing the seven Panzer Divisions of Army Group A to make an independent strategic interlude. To Guderian's chagrin, this was initially completely removed from the new plan. The "Yellow Plan No. 4" was issued on 24 February, and the crossing of the Meuse at Sedan was supposed to be captured by infantry divisions on the eighth day of the invasion.

It was not until after much debate that the motorized rifle regiment of the Panzer Division was given the option to establish a bridgehead here on the fourth day after the invasion. Even now, the breakthrough and advance towards the English Channel can begin only on the 9th day, and the stay in the middle 5 days is intended so that a sufficient number of infantry divisions can catch up and create a continuous front with armored forces.

Even with adaptation to more conventional methods, the new strategy provoked protests from most German generals. They considered it irresponsible to concentrate their forces in the same position, and that it was impossible for the interspersed troops to be adequately supplied, and that these already insufficient supply routes could be easily cut off by the French. If the Allied response was not as expected by the Germans, the offensive could end up being catastrophic. However, their objections were ignored.

Halder believed that since the strategic position of the German army seemed hopeless, in any case, even a slight chance of achieving a decisive victory was better than defeat by complete inaction. The change in adaptation also implied that it would make it easier for the Allies to flee to the south. Halder noted that the German victory would have been easier if this had been the case, as it would have been a huge blow to the reputation of the abandoned Low Countries Entente (colloquially known as the Anglo-French alliance of 1940).

In addition, the combat effectiveness of the German army will remain the same, and it will be possible to carry out the "red plan", after which an all-out attack on France will be carried out. However, decisions in this regard will have to be postponed until the successful completion of the "yellow programme". In fact, the detailed implementation plan of the German army included only the first 9 days of operations; There is a fixed timetable to determine the path forward. According to the traditional "mission command", this relies on the judgment and actions of the field commander. This uncertainty can have a huge impact on the actual course of events.

In April 1940, for strategic reasons, the German army carried out Operation Wither, attacking the neutral countries of Denmark and Norway. The British, French, and Free Polish Army responded by operating in support of the Norwegians.

At this time, the Dutch, Belgian, Luxembourg, French and British expeditionary forces had a total of 135 divisions (including 103 divisions of the French and British armies, organized into 3 army groups, 3,469 tanks, 2,000 aircraft, and could use more than 1,000 aircraft in the British Isles to support the battle, which was comparable to the German army in terms of strength. However, Britain and France pursued a policy of appeasement for a long time and were not well prepared for war.

The Allied High Command's plan of operation, codenamed D, was a conservative miscalculation, focusing on defending against the main German assault on Belgium, which would be the main battlefield for both sides. According to Plan D, the Allies deployed their main forces at the northern end of the Franco-Belgian border and the northern provinces of France, and if the Germans carried out a major assault on Belgium, the Allied forces of the five countries would work together to block the German attack; Most of the other forces were deployed on the Maginot Line in the south, and in the event of a frontal German attack on the Maginot Line, they relied on strong fortifications to defend them; In the middle section, it relied on the natural dangers of the Ardennes Mountains and the Maas River, leaving only the weaker combat units to garrison.

France has mobilized about a third of its male population between the ages of 20 and 45, bringing its armed forces to more than 6,000,000 men, more than the 5,400,000 of the entire Wehrmacht. But only 2,200,000 of these troops were deployed in the north, although together with British, Belgian and Dutch troops, totalled more than 3,300,000.

By 10 May, 93 French, 22 Belgian, 10 British, and 9 Dutch divisions were in the north, for a total of 134 divisions, including 6 armoured and 24 motorized. An additional 22 divisions are being trained or equipped in wartime emergencies (excluding restructured units), including 2 Polish and 1 Czech.