The greatest failing of the French Army in 1940 was in command and control and their understanding of modern tactics. The first is because they had conspicuously failed to keep pace with improvements in technology and the second can be laid squarely at the feet of the great obstacle to French defence thinking; the Maginot Line.
The French Army in 1940 had a command and control system that was little better than it had in 1918 and was quite possibly worse. The Orders were usually sent by dispatch riders. The headquarters of the Commander in Chief of the French Army, General Gamelin, did not even have a radio. When asked about the lack a radio he said that it might have revealed the location of his HQ. Prior to the German offensive reports were taking up to 48 hours to reach Gamelin’s headquarters and his orders another 48 hours to reach front line commands. So even before the massive disruption of the German attack the French were struggling to respond to something at their front in less than 5 days. In five days the Germans were able to conquer Holland, reach the outskirts of Brussels and reach Montcornet; half way to the English Channel!
Had the French had a more satisfactory communications system they might have been able to respond to the German attack better. Their army was very limited in motorised transport; the French armies of 1940 for the most part literally marched north into Belgium, but the bulk of the German Army was likewise limited in motorised transport so this was not disastrous handicap.
In 1933 Colonel Charles de Gaulle published his book ‘Towards a Professional Army’. The title alone is clear proof of de Gaulle’s lack of talent when it came to winning friends and influencing opinions; if you want to persuade your military superiors to change their ideas it does not help to start by implying that they are unprofessional. The senior commanders of the French Army were so incensed that they ordered that all future articles or lectures by serving officers needed to be approved by them prior to publication, effectively quashing discussion.
The armoured and motorised force proposed by de Gaulle had another problem getting funding; the Maginot Line. French Politicians did not want to spend large sums on money on an armoured force when they had already spent an enormous sum on the border defences. Critics asked if this new force was to be put in front of or behind the Maginot Line. Nevertheless by May 1940 France did manage to field three armoured divisions, or more correctly three ‘light mechanised divisions’ consisting of one tank brigade, a motorised infantry brigade, a regiment of artillery and a regiment of armoured cars and assigned the role previously occupied by the cavalry; reconnaissance and scouting. Had they been given the principle counter-offensive role of the Army things might have been different; had they been tasked with promptly attacking the German breakthroughs at the bridgeheads over the Meuse they could have made things very difficult for the German Panzer divisions, possibly even stalled the German offensive. But that would have required prompt responses to events by the French High Command.
The German Panzer offensive was directed through the Ardennes region, a region the French ruled out as a rout of attack because of its hilly nature, narrow and poor quality roads. When they did attack the result was an enormous traffic jam behind the German spearheads, a highly visible, very vulnerable, traffic jam that was actually reported by French reconnaissance aircraft flying over the area. The reports were discounted because they did not conform to French High Command’s expectations of where the German attack would come.
If the German river crossings of the Meuse had been promptly met by armoured forces, and the panzer and truck convoys behind, stuck on the narrow and twisting roads of the Ardennes been bombed and strafed by the French air force the entire offensive could have died there and then. Instead the crossings and the convoys were unhindered by air attacks.
Not only did the French Air Force high command ignore reports of tanks moving through the Ardennes but following the Luftwaffe attacks on French Airfields on the first morning of the attack a very large number of French Aircraft were flown south to airfields out of range of German attacks without any record being kept of where they were being sent. So although the French had aircraft as good as the Germans, and in numbers actually greater than the Germans, they at no stage had air superiority over the battlefield or even came close to challenging German air superiority.
As to the Maginot Line itself, most of its armaments were facing forwards and could not provide all round defence and it did not contain large numbers of troops ready to counterattack any German breach in the line; so once it had failed anywhere and the Germans were in behind the line it was doomed and the troops left manning static defences facing the wrong way. Besides which the Maginot Line could be built all the way to the English Channel without cutting through French industrial and mining areas; so the Germans didn’t need to breach the French defences, they just drove around them.
Without the Maginot line the French could have been exploring the best use of tanks right from the end of the First World War. Instead of large numbers of slow moving tanks spread amongst the infantry they could have had an armoured spearhead at the front of their army, and would have had the money to afford ten or more armoured divisions in 1938 when Hitler had only three. With such a balance of forces the Munich conference could have had a very different outcome and a German offensive in 1940 would never have eventuated.