On the eve of May 10, 1940, the German army in its offensive array against the Allies was divided into three groups of armies. By far the most efficient forces were naturally mobilized in areas where the OKW had decided to fight its decisive maneuvering battle. Therefore, since against Maginot, where the enemy was fearfully barricaded, nothing conclusive could be achieved, Hitler had established that the group of armies “C” would be in charge of facing, for the moment, in a static way the chain of Maginot fortifications., under the orders of col. gen. Von Leeb. Since no shock actions would be pursued on this side for a long time, von Leeb’s army corps completely lacked both armored and motorized forces. Indeed, von Leeb had only 10 infantry divisions of the 16th Army, 20 infantry divisions of the 1st Army and finally another 10 infantry divisions of the 7th Army. The 10 armored and 4 motorized divisions of the Wehrmacht were instead concentrated in the two groups of armies “A” and “B”. More specifically, since Hitler had devised a daring and ingenious plan of attack, overturning the traditional scheme of the Schlieffen plan by strengthening the left rather than the right of his alignment much more (v.world War: Campagna di Francia, in this App.), The armored vehicles were fully deployed to the two army groups “A” and “B”. And since the “A” army formed the left of the attack device, this army, under col. gen. von Rundstedt, 7 Panzer divisions were assigned, divided into three armies (armed by the armored troops gen. Hoth, Reinhardt, Guderian) and 3 motorized divisions, making up the army of the gen. Wittersheim. The “B” army, employed by col. gen. von Bock, had a more modest mission: that of occupying Holland, of disorienting the allied command and of supporting the decisive action of the “A” army from the north, on the right of the Germanic deployment; therefore to this group of only 3 armored and 1 motorized divisions were assigned (the 3rd and 4th Panzer with the motorized 20th constituted Hoeppner’s armored army). The third group of armies “C”, employed by von Leeb, having to perform, as we have seen, a mainly static function, lacked armored and motorized corps, did not have a Luftflotte, which the other two groups were equipped with: the 2nd Luftflotte (A. von Kesselring) to group “B”), the 3rd Luftflotte (gen. Sperrle) to group “A”; von Leeb also had no maneuver reserves, while the other two groups were followed by the general reserves of the OKW, formed by 15 infantry divisions.
Apart from the equipment of materials, not comparable with those of the enemy, the French deployment left much to be desired also from a tactical-strategic point of view. The allied troops were divided for operational purposes, into three large groups of armies: 1st group of armies, under the orders of gen. Billotte, 2nd army group (gen. Prételat), 3rd group (gen. Besson). The first group, more important, was to cover the territory between the mouths of the Meuse and Longuyon; the second group was entrusted with covering the Maginot, between Longuyon and Sélestat (thus excluding the short Montmédy-Longuyon section, pertaining to the 1st group); on the third, the remainder of the Maginot and the entire Franco-Swiss border. The first group of armies had to bear, according to all likelihood, the greatest weight of the struggle between Breda and Namur. Well, to this first group were attributed, including 6 reserve, 45 divisions; to the second and third groups, together, 54. The most efficient troops, from the point of view of mechanization, were however seconded to the 1st armed group of the Billotte, which had 3 mechanized light divisions and 4 motorized infantry divisions in line, and 3 motorized infantry divisions in reserve; the Prételat and Besson groups, on the other hand, did not have any corresponding mechanized units. Moreover, as for the 37 large active infantry units, at the time of the German attack, only 15 were assigned to the 1st group, 9 to the 2nd group, 1 to the 3rd group; 11 remained available in the general reserve of Gamelin and Georges. So that at the decisive moment of the German attack, about 40% only of the best infantry in France participated in the decisive initial fights. The picture is aggravated if we reflect that of the three real armored divisions, none were on line on 10 May 1940. These three large units were placed in the general reserve, near Châlons-sur-Marne, at the disposal of the supreme command. Such a decision made it necessary to rely on dominance, or, at least on air balance, so that the three units were able to participate in the battle when needed. However, given the net imbalance, the French command was ruinously hindered in its intention to fuel the operations using the roads and railways, which were made impracticable by the German air attacks in the first three days of the offensive.
According to Militarynous, the real war on the western front began at 5:35 minutes on May 10, 1940. Almost simultaneously with the start of operations by the German armed forces, Holland and Belgium were invaded. The French and British military leaders – gen. Gamelin and Lord Gort – met to determine the common conduct of operations.
Two solutions were presented to the Allies: wait for the enemy attack on French territory, in pre-established and fortified positions, or enter Belgian territory, with the dual purpose of avoiding the destruction of the twenty Belgian divisions and protecting the coast facing Great Britain. The French generalissimo preferred to stick to this second solution. (For operations in the Belgian and Dutch territories, see Belgium ; Holland, in this App.).
Following the rapid success achieved by the Germans in the Dutch and Belgian territories, and the serious setback suffered by the 9th French army (Gen. Corap), on the average Meuse, on the days from 12 to 15 May, a setback that opened the way to the Germans. in the heart of France, the situation of the French army was quickly and seriously affected, especially as the breach opened in the Meuse line, in front of Sedan, was, with a further effort of German armored formations, very validly supported by the aviation, enlarged for about a hundred kilometers, extending northwards, until a little south of Maubeuge.