As I understand, the Maginot Line was a series of fortifications constructed on France's eastern border with Germany after the First World War. The idea was to have a border lined with heavily fortified positions from which the French Army could operate in the event of a German invasion.
I've often seen the Maginot Line portrayed as an example of inflexible military strategy on the part of the French Army. The story goes that in the interwar period, militaries had moved on from trench warfare and moved into an era in which increased mechanization meant that armies were fast enough to break through and encircle enemy armies (particularly infantry divisions). The implication is typically that the Maginot Line might have been very useful in the First World War, but was useless by the Second.
However, I can't help but notice that the Wehrmacht avoided the Maginot fortifications when they invaded France in May of 1940. As I understand it (using this map for reference), the Germans attacked the Netherlands and Belgium in order to draw the French Army north, and then launched an invasion through Sector 5 of the Maginot, through the Ardennes, which lacked the defensive fortifications of parts of the line like Verdun, Metz, and Strasbourg. This ultimately resulted in the majority of French Army being encircled, and the eventual capitulation of the French government.
The reason I've seen given for why that part of the border was not heavily fortified was that the French military didn't regard an invasion through the Ardennes as a serious possibility (in part due to the failure of the Schlieffen Plan during the First World War).
But my question is: was the Maginot Line a bad idea from the start? Had warfare really moved on from trenches and fortified positions? Or is it simply that the Maginot Line was not extended far enough (e.g. into northern France) that Germany was able to win so quickly?
I'm asking this question because the story of "French military command was rigid and inflexible in their thinking, evidenced by the fact that they endorsed obviously doomed projects like the Maginot Line" seems less plausible to me given that it seems like the German Army went through a lot of trouble to avoid the Maginot fortifications altogether.
This makes me wonder if historians have been a bit harsh on French High Command, with many seeming to agree that it was the incompetence of people like Gamelin and Weygand that caused France's quick capitulation.
PART 1
The Maginot Line was a good strategy based on the context of the time, and for the cost of 2-3% of France's military budget was money well spent.
To understand why u/RepresentativePop, you really need to understand the things that hamstrung French planning during and in-between the world wars. To this end I would highly recommend the writings of Robert Doughty and Eugenia Kieseling (see references at the end). These sources are the most modern historiography on the subject and avoid the "pop history" explanations that were popularised by writers in the 1950s and 60s, painting a much more accurate picture. A good example of the pop history narrative that links back to the part of your question on section 5 of the Maginot is the famous quote by Pétain on the Ardennes. It has been highlighted to show how out of touch the the army leadership was, however only the first part of the quote is ever used. The second half is just as important. Bold for emphasis: "The Ardennes is impenetrable so long as it's properly defended." Not an inaccurate statement.
Maginot Line
First, let's address the Maginot Line. The French examined the idea of extending the Maginot Line along the Belgian border in some detail but rejected the idea, partly for political reasons to do with Belgian neutrality but also for some sound strategic reasons. Fun fact... the French actually offered to pay for the cost of fortifying the Ardennes region during the 1930's but this was declined by Belgium. Moving on:
(A) The terrain on the Franco-Belgian border was completely unsuited to defence and is largely open fields intersected by rivers making it exceedingly difficult to fortify. It also has a high water table meaning it was impractical to build underground, and as the area along the Franco-Belgian border is heavily industrialised, it would have caused a lot of disruption to vital industry had they begun building forts in the area.
(B) The main industrial and population centres of France are in the North-East of the country which presents a significant strategic problem. Here is a link showing a map of France, within the red circle lies 50% of France's GDP today: https://imgur.com/a/92gJx Back in 1940 industry was even more concentrated in the North-East, and as Doughty lays out early in Seeds of Disaster and Breaking Point: Sedan, ninety percent of France's cloth and woollen industry was north of the Seine as were the majority of the chemical industry, 100% of the automobile factories and 100% of the aircraft industry. As noted before, lots of population lived near these industrial centres and as such they could not be lightly surrendered to the enemy. Aside from industry, this region also contained lots of natural resources, 75% of France's coal came from here and all of France's iron ore came from the Briey-Longwy basin in Lorraine. The French were aware they needed to move the battle away from this area if they were to have any chance in holding until their allies could come to their aid.
(C) Holding until here allies came to her aid was the most viable strategy for France. They knew in a 1 on 1 fight with Germany, they would be in serious trouble as Germany had more population and industry than France did (roughly 40 million compared to roughly 60 million, meaning Germany could call up twice as men of military age as France in this time period). France actually mobilised 300,000 less soldiers in 1940 than in 1914 (see the "Hollow Years"). Fortifying and sitting on the border meant the battle would occur in some of the most industrially valuable parts of France, and France would not be able to hold until help came. So the French plan was to push the front forward and fight the Germans in Belgian, not French territory, along the Dyle river (in what was called Plan D or the Dyle Plan).
(D) Regarding your question about fortifications... The French command was fully aware that any "line", attacked with enough strength, could be breached. Gamelin (French Commander in Chief) wrote in 1935, “from 1915… whenever the necessary means were judiciously employed, one always broke a front.” (Kielsing, Arming Against Hitler) When the Maginot Line was completed in 1935 it was impenetrable to the German army of the day but the French had no illusions about the sanctity of fortifications. If they had extended the line along the Belgian border the forts in exposed areas (fields and rivers remember) would have been broken quickly by heavy artillery, bombers etc. and the French high command knew this in part due to what had happened to the Belgian forts at Liege in 1914 and their own experiences with the forts surrounding Verdun in 1916.
(E) Defending the border would present a significantly longer front to defend than moving into Belgium and defending along the Dyle river. This was a problem due to what I mentioned concerning the number of men that France could field. Besides a shorter front, the French needed the extra 22 divisions of the Belgian Army plus whatever the Dutch could field to even out the manpower imbalance.
The Maginot Line was a force multiplier in today's parlance, designed to screen the border regions, allow the army to mobilise and funnel the Germans through Belgium where the French army's mobile elements could manoeuvre and counter the German advance. It was a practical and useful response to the strategic challenges faced by France at the time. It actually allowed France to garrison the Franco-German border with only 15% of its total number of soldiers.
Mobile Warfare (Or: Did the French Just Use Tanks as Infantry Support?)
Now let's move on to the way the French army operated in the field. Perhaps the most pervasive criticism of the French in 1940 was that they failed to understand the changes that had taken place in warfare since WW1, chiefly that they hadn't embraced combined arms and mobile warfare. However as Kiesling shows, the French military was well aware of new theories on mobile warfare. A resurgent Germany forced on France the problem of translating strategic ideas into a set of specific actions. However between theory and practice there were political, social and economic obstacles that caused a number of problems. France was limited by her political institutions, history and other factors, as were other powers.
It's worth noting that in 1940 France had:
7 x Motorised Infantry Divisions
5 x Mechanised Cavalry Divisions
4 x DCr or Division Cuirassée de Réserve (a heavy armoured division, light on infantry)
3 x DLM or Division Légère Mécanique (a well balanced medium armoured division including motorised infantry, artillery, AA and anti-tank sections)
In addition to this there were indeed tanks designed for infantry support, these consisted of 30 independent tank battalions generally deployed in regiments of two battalions each and assigned to army and corps reserve formations.
The DCr and DLMs were the functional equivalent of the German Panzer divisions, that is the French envisaged using these in the breakthrough phase of battle. France had 7 of these divisions to the 10 Panzer divisions Germany had. When you account for the differences in population and the relative size of the two armies, they were therefore roughly equal in terms of mechanisation.
There's certainly more to be said, but here's an old answer from /u/Georgy_K_Zhukov that covers the issue of the Maginot Line in context. Here's another answer from /u/vonadler approaching the matter from a different perspective.
Amazing stuff guys. Thank you so much!!
