The attack on the Netherlands, Belgium, Luxemburg and France started on May 10th 1940 and within six weeks all these nations had been defeated with British and French forces being evacuated at Dunkirk. Blitzkrieg had torn through both the French Army and the British Expeditionary Force (BEF). Prior to the attack on France, German forces had attacked the Netherlands, Luxemburg and Belgium. All three had quickly surrendered to a vastly superior enemy and to save their countries from extensive damage.
The main military power in Western Europe was France. In the inter-war years, the French Staff College was considered to be one of the world's premier military colleges. Officers who went through the college were taught that defence was superior to attack and that any attack, as seen in World War One, would be slow and ponderous with many casualties involved. Tanks were seen as a means of supporting the infantry or as a means of supplementing reconnaissance units. The French put great faith in what they called the “continuous line” - literally a seemingly impregnable line of soldiers who were embedded in very strong defensive lines. In theory, breaking through this continuous line would be extremely difficult and costly in manpower - hence why the defensive was seen as being superior to the offensive.
The most visible sign of this defensive mentality within France was the Maginot Line. This was started in 1929 and named after the Minister of War of the time. The Maginot Line ran from Basle to Longuyon but it was not a 'land battleship' for the whole of this distance.
From Basle to Haguenau, the River Rhine acted as the frontier between Germany and France - and also as a very formidable defensive barrier. Therefore, between Basle and Haguenau, the Maginot Line was no more than a dense network of pillboxes.
From Haguenau to Longuyon, the Line was a massive fort that had many similarities to a battleship - self-raising gun turrets, ammunition hoists etc. In front of the Maginot Line, nearer to the German border, the land had been sculpted so that a massive anti-tank barrier had been built. Such was the size of the Maginot Line, that some of the individual forts within it, needed a garrison of near battalion strength.
However, once the Maginot Line ended, the French border as far as the Channel was poorly protected. Such was the French belief in the Maginot Line and the superiority of defence, it never occurred to them that an army could come through the 'impenetrable' Ardennes and simply bypass the Maginot Line. Attacked from the front, the Maginot Line would have been a formidable opponent - but not if it was either bypassed or attacked from the rear.
By May 1940, one in seven of the divisions in the northeast sector of France was a fortress division only capable of fighting from its fortifications. Therefore, the 'Maginot Mentality' (the superiority of the defence) automatically took out of the French Army a large number of men, about 15% of the French Army. The number of Germans manning the Siegfried Line opposite the Maginot Line was considerably smaller.
Dutch and Belgium officers frequently went to the French Staff College and it was only natural that the ideas of the French would percolate into the ideas adopted by their armies.
In the build up to May 10th, 1940, those armies in the field had the following strengths:
The Dutch Army comprised of 8 divisions, with 2 in reserve; none of these was an armoured division. It faced the power of von Bock's Army Group B.
The Belgium Army had 18 divisions with 4 in reserve. None of these was an armoured division.
The French Army was a major opponent on paper.
The First Army Group was commanded by General Billotte. This comprised of 22 divisions and spread from Longuyon to Maulde on the Belgium border.
Based behind the Maginot Line was the Second Army Group commanded by General Prételat. This had 43 French divisions in it and 1 British division. It had units based as widely apart as the Swiss border near Basle to Longuyon, southwest of the Luxemburg border.
Protecting the Channel ports of Dunkirk and Calais was the Seventh Army Group commanded by General Giraud. This comprised of 7 divisions.
The French had 22 divisions in reserve.
Supporting the French, and based between the First and Seventh Army Groups was the BEF commanded by Lord Gort. This comprised of 9 divisions.
Therefore, the Germans faced a total military force of some 108 divisions.
The French First Army faced Army Group A commanded by General von Rundstedt. This comprised of 45 divisions, including 7 armoured divisions. It was supported by Air Fleet III commanded by Sperrle.
Against the French Second Army was Germany's Army Group C commanded by General von Leeb. This comprised of 19 divisions.
Germany's Army Group B, commanded by General von Bock, was based in north Europe and had to pass through the Netherlands and Belgium before it faced the French. Bock's force comprised 29 divisions, including 3 armoured divisions. It was supported by Air Fleet II commanded by Kesselring.
Against the French and BEF, the Germans could muster 93 divisions including 10 armoured divisions.
The Germans had 42 divisions in reserve.
The French Chief of Armed Forces was General Gamelin. His German opponent was Field Marshall von Brauchitsch and his Chief-of-Staff was General Halder.
The success of the Germans has frequently been put down to her superiority in weaponry like tanks and artillery guns. This was not the case.
The French had 10,700 artillery guns in May 1940 (though 50% were from World War One) and the British had 1,280. Including those the Belgium and Dutch armies had, the Allies could call on 13,974. The Germans had a total of 7,378 artillery guns including the highly regarded 105 mm field gun.
The same was true with regards to tanks. The French had a total of 3,254 tanks in the spring of 1940 and the British 640. The Germans could call on a total of 2,493 tanks.
With such superiority, why did the Allies fail so badly? The numbers were essentially irrelevant when compared to the way these weapons were used. The Germans used artillery that was designed to be mobile while the French and British did not. Probably the greatest difference in usage was how each side used tanks. It is frequently assumed that the German tanks used in the attack on Western Europe were superior to French tanks. This was not the case. Where there was a difference was in the way both sides used tanks. The Germans spearheaded attacks using tanks while the French used tanks to support the infantry - therefore tanks such as the Char B were reduced to operating at the speed at which infantrymen operated, despite the Char B being a very capable tank that would have held its own against most German tanks.
The Germans also had a major advantage in the air. The French had failed to develop its air force in the inter-war years and by May 1940, only had 1,200 planes - all of which were inferior to the modern Luftwaffe. The single-seat fighters (the Morane, Bloch and Dewoitine) were no match for the Me 109 and Me 110. The British had 500 planes in France, of which 130 were fighters. Again, the Defiant and Gladiator were no match for the Luftwaffe's fighter planes. The Hurricane was based in France but it had not been tested in combat and was yet to make its mark. In total, the Germans could call on 3,200 planes for an attack on Western Europe.