WI: Longer Maginot Line

[Hoist40]

One problem with the French WW2 War plans when it comes to Belgium is that the French did not want to fight another war on their northern border because it was too close to their northern industrial area which was devastated during WW1 and greatly weakened the French war effort. That is a big reason why they did not build significant fortifications on the border, even if built, the Germans could put the northern industrial area within artillery range.

The French and British WW2 plan was to advance into Belgium and fight there but obviously this was not something to make the Belgium happy since they also were devastated by fighting in WW1 on their territory, so the Belgium’s wanted neutrality.

The French and British also counted on Belgium military fighting and holding the Ardennes even though that area was not critical to Belgium’s defenses.

So there were multiple problems caused by the different interests of the French, British and Belgium’s. The French did not want to fight on French territory. The Belgium’s did not want the French and the British fighting on Belgium territory. The British did not want to fight to the last to defend France. The French and British wanted Belgium to stop or slow down the Germans in the Ardennes but the Ardennes had no significant in the defense of Belgium.
　

 

[BlondieBC]

The French and British WW2 plan was to advance into Belgium and fight there but obviously this was not something to make the Belgium happy since they also were devastated by fighting in WW1 on their territory, so the Belgium’s wanted neutrality.

It is a small point, but outside of Ypres area, most of Belgium was more devastated by the blockade by England and the looting by the Germans. The Germans were pretty systematic in demetalizing Belgium.

 

[Dan Reilly The Great]

As has been said, the real failing wasn't in keeping the maginot line at the length that it was, it was that the Commanders of the French army as well as the French political leadership were so mind numbingly incompetent in how they handled the opening phases of the war that no defensive plan, no matter how well formulated.


The French are not cheese eating surrender monkeys, but they were certainly saddled with some real numbskulls in the run up to the war.

 

[CalBear]

You are correct. The line was a perfect defense for the previous war.

Too bad the Germans were not fighting the previous war.

Actually the Line was a very powerful defensive structure, this is best shown by the way the Heer avioded it like the Pox. The French, contrary to post-war beliefs, had no intention of sitting behind the Line and praying that the Germans ran out of ammo. The goal was to stop the initial Genam attack, use the Line to hold the enemy in place and then destroy them with fire and use the Line as a stable base of operation for offensive maneuver warfare.

What caused the French failure was a combination of errors, some military (including those by the British forces), some political, the Fog of War caused by the unexpected location and method of the Heer's attack, and superior tactics and battle planning by the Heer staff. Any one of these could have been overcome, all of them proved to be fatal.

 

[Athelstane]

I hope it's becoming clear on this thread by now: the problem really was not with the Maginot Line, which in fact more or less accomplished what it was supposed to accomplish: It channeled a German attack away from the common Franco-German border. It allowed the economization of troops, freeing up more for a strategic maneuver force which could be deployed to the plains of Belgium. It was not the fault of the planners of the Line that Gamelin and the French general staff failed to take advantage of that economy. And, more to the point: German attacks mounted directly on the Line met with little success.

Three billion francs were dumped into the Maginot Line, all at the opportunity cost of modernization of French forces otherwise, particularly as regards mechanization. Much more than double that would have been required to extend the line to the Channel, given the high water table noted by others. In any event, French war planners counted on the increasingly impressive Belgium fortifications being completed in eastern Belgium to hold up any German attack until the French Army (and BEF) could be deployed to Belgium.

No, the extra billions that would have been shoveled and poured into the marshy soil of Artois would have been better spent building more capable armored and mechanized divisions, more robust command and control, and more capable ground attack air support capabilities. It could have been spent on combined arms exercises to hone and refine those capabilities, and develop appropriate tactics to exploit them. And it would have cost little money to promote army commanders who could and would actually take advantage of such capabilities.

The German victory in 1940 was certainly not inevitable, and the Maginot Line, often unfairly disparaged for failing to accomplish what it was never intended to accomplish, did not make it inevitable. Rather, it was the nature of the French Army itself, and how it was deployed by Maurice Gamelin, that did so much to make the German breakthrough at Sedan possible, and so readily exploited in turn.

 

[LOTLOF]

What people tend to forget is that 'Plan D' the Allied plan to rush north and fight the Germans on the Meuse would have actually been the correct response to the ORIGINAL German invasion plan. Until Manstein came up with the idea for his sickle cut through the Ardennes the operational plan was to invade through Belgium to try and capture the Channel ports. If the Germans had stuck to their original strategy they would have met the BEF, French, and Belgian armies head on and been forced to try and slug their way through. They might or might not have succeeded, but this sort of straight on fight would have played into allied strengths and made a battle of encirclement pretty much impossible.

The reason for the disaster was not the weakness of the Maginot Line, lack of numbers, or inferiority of equipment. The issues was that Gamelin and the Allied High Command were committed to a plan that would only work if the enemy did exactly what they expected them to. It is always very dangerous to assume the enemy cannot surprise you.

Their fatal flaw was that they complately lacked flexibility and were not able to respond when the Germans hit them in an unexpected area with an unexpected strategy. If the lessons from Poland, and more recently Norway, had been understood and the Allies had more flexibility they could have at least avoided the fall of France.

 

[TyranicusMaximus]

More money invested in the line means less money for the rest of the military, and more importantly for the French electorate, less social spending.

Certainly there's more money that can be squeezed from somewhere with the right POD, but that much of an extension to the Channel Coast will force a diversion of government funds elsewhere.

I remember looking through Douglas's posts, and he posted a pretty lengthy debunking of the myths behind the Maginot Line.

 

[Athelstane]

= Wrong thinking, thinking in hint sight.

Which means the Maginot line did exactly what it was build, the whole lline worked perfectly and was never intended to be extend to the Channel coast.
The line was part of the French strategy:
Stop immediate invasion of France by German troops, like happened in 1870 and 1914.
Force any invasion through Belgium and fight there, on Belgium soil a war of manuvre. With this strategy you prevent the devastation of you own country.
That thing did not worked out a planned is an other reason, but not the Maginot line or that it stoped at the Belgian border.

And put this way, it really highlights the stupidity of Leopold III and the Belgian government in 1936-1940: the construction of the Maginot Line (and later, the weaker Siegfried Line across from it) virtually guaranteed that any future Franco-German War would be fought right where the last one had been fought: on Belgian soil. German general staff planners would hardly be stupid enough to commit their major attack into the teeth of such formidable fortifications (in such difficult terrain), any more than their predecessors had desired to attack directly into French fortifications of Toul-Verdun on the old Alsace-Lorraine border.

The idea that a mere declaration of neutrality would be any more effective than it had been in 1914 in overcoming overwhelming strategic realities simply boggles the mind. And yet, that was the mindset of too many Belgian leaders in the late 30's. It took the roar of bombs and the crashing of tanks through border stations on May 10, 1940 for them to realize their mistake, far too late.

 

[SergeantHeretic]

Actually the Line was a very powerful defensive structure, this is best shown by the way the Heer avioded it like the Pox. The French, contrary to post-war beliefs, had no intention of sitting behind the Line and praying that the Germans ran out of ammo. The goal was to stop the initial Genam attack, use the Line to hold the enemy in place and then destroy them with fire and use the Line as a stable base of operation for offensive maneuver warfare.

What caused the French failure was a combination of errors, some military (including those by the British forces), some political, the Fog of War caused by the unexpected location and method of the Heer's attack, and superior tactics and battle planning by the Heer staff. Any one of these could have been overcome, all of them proved to be fatal.

So basically it was just one of those things. A serious case of stuff happening, nothing anyone could really do.

 

[Athelstane]

What people tend to forget is that 'Plan D' the Allied plan to rush north and fight the Germans on the Meuse would have actually been the correct response to the ORIGINAL German invasion plan. Until Manstein came up with the idea for his sickle cut through the Ardennes the operational plan was to invade through Belgium to try and capture the Channel ports. If the Germans had stuck to their original strategy they would have met the BEF, French, and Belgian armies head on and been forced to try and slug their way through. They might or might not have succeeded, but this sort of straight on fight would have played into allied strengths and made a battle of encirclement pretty much impossible.

The reason for the disaster was not the weakness of the Maginot Line, lack of numbers, or inferiority of equipment. The issues was that Gamelin and the Allied High Command were committed to a plan that would only work if the enemy did exactly what they expected them to. It is always very dangerous to assume the enemy cannot surprise you.

Their fatal flaw was that they complately lacked flexibility and were not able to respond when the Germans hit them in an unexpected area with an unexpected strategy. If the lessons from Poland, and more recently Norway, had been understood and the Allies had more flexibility they could have at least avoided the fall of France.

That's an excellent point. Had Hitler stayed with the original Fall Yellow plan, they would have done...more or less what the Allies expected them to do., And were deployed to meet. Had Hitler invaded in October or November of 1939, as he wanted...the result would almost certainly have been stalemate at best, and not just because French morale was higher, and German tank production not yet sufficiently deployed.

The inflexibility of Gamelin and the French general staff really were the fatal weakness of the Western allies. Sure, they were inferior in air power, but by itself that would probably not have been enough to ensure a victory, or a fast one, at any rate. The French had good tanks, albeit distributed out among infantry divisions for the most part. But what was fatal was the rigid mindset of the French high command. They expected the Germans to act in a certain way, and had no plan, no flexibility for the possibility that they might do otherwise. The Germans, to their credit, were willing to take much greater risks.

 

[SergeantHeretic]

That's an excellent point. Had Hitler stayed with the original Fall Yellow plan, they would have done...more or less what the Allies expected them to do., And were deployed to meet. Had Hitler invaded in October or November of 1939, as he wanted...the result would almost certainly have been stalemate at best, and not just because French morale was higher, and German tank production not yet sufficiently deployed.

The inflexibility of Gamelin and the French general staff really were the fatal weakness of the Western allies. Sure, they were inferior in air power, but by itself that would probably not have been enough to ensure a victory, or a fast one, at any rate. The French had good tanks, albeit distributed out among infantry divisions for the most part. But what was fatal was the rigid mindset of the French high command. They expected the Germans to act in a certain way, and had no plan, no flexibility for the possibility that they might do otherwise. The Germans, to their credit, were willing to take much greater risks.

Now THERE is an idea for a timeline what aint got no Alien Space Bats. :What if HItler stuck to "Fall Yellow"?

 

[iddt3]

Now THERE is an idea for a timeline what aint got no Alien Space Bats. :What if Hitler stuck to "Fall Yellow"?

It certainly would be interesting, especially if it doesn't go the Soviet wank route (which is unfortunately I think the most likely outcome) and we end up with a very different post war Europe.

 

[SergeantHeretic]

It certainly would be interesting, especially if it doesn't go the Soviet wank route (which is unfortunately I think the most likely outcome) and we end up with a very different post war Europe.

If Hitler sticks to "Fall yellow" and advances the Wehrmacht into the teeth of the British. French and Belgian armies. They will then eat his lunch leaving Germany open to the Soviets, so yeah, Soviet wank, ahoy.

 

[eighthgear]

As in the Franco-Prussian War, the French were completely capable of putting up a good fight to the Germans, and even capable of repulsing them, but were betrayed by poor leadership.

 

[SergeantHeretic]

As in the Franco-Prussian War, the French were completely capable of putting up a good fight to the Germans, and even capable of repulsing them, but were betrayed by poor leadership.

AN otherwise fully capable and modern army screwed over by bad leadership?

Looks like there was a lot of that going around.

 

[corditeman]

Very interesting...but shtoopid!

A quote from a comic German watching something inane.

Back to the point.

Krupps did build some rather nasty 'bunker buster' guns to smash through up to seven metres of concrete. I thought this too good to miss so used them and other weapons on the Maginot Line in the WW2 part of 'HMS Heligoland'. The moral is that no fortification is completely invulnerable in the face of continued technical development. In OTL, the guns were used to shatter Soviet fortresses in the Crimea.

The Maginot Line as built was excellent, but it became an excuse for cutbacks in the mobile field army. Otherwise, even the Ardennes offensive could have been halted. Gamelin was the kind of commander every army suffers from and should make allowances for.

 

[Cook]

What if the French threw sufficient resources at the Line to extend it that far north? What impact does this have when the Nazis go west?

When the Maginot Line was designed in the 1920s Belgium was an integral ally of France and, as conceived and built, The Line linked up with the Belgian border defences that run through The Ardennes and along the line of the river Meuse, north to the Dutch border, the northern most fortress being Eben-Emael. The soil conditions of northern France played no part in the decision; the claim that the ground in the north was too wet and soft to build fortifications on is, as the civil engineering joke goes, without foundation. Eban-Emael defended against any German attempt to flank the Meuse defences by cutting through the tail of the Netherlands at Maastricht, if they tried cutting through Holland any further north they’d find bridges blown, the land flooded and the Dutch army withdrawing into ‘Fortress Holland’; there was no easy road further north.

The greatest concentration of French industry and mining lay in the region between Paris and Belgium, in the area straddling the border around Lille-Valenciennes; in what Clausewitz referred to as ‘the heart of France’. A series of defensive fortifications in this area would have exposed French industries and mining to the same destruction they’d suffered in the First World War, the very thing the Maginot defences were intended to prevent. As it was, following the withdrawal of Belgium from their alliance, a series of secondary defensive works were commenced along the Franco-Belgian border but these proved to be of no significant value during the invasion.

The thinking behind the Maginot Line was quite obviously a product of France’s experiences of the First World War. More specifically, it was based of the French army’s experience of the battle of Verdun. More French officers rotated through the battle of Verdun than any other battle of the war and while the French army did not break at Verdun, it was severely damaged by the battle. So much so that by 1918 it was the British army that was the principle attacking force on the allied side, not the French. As a consequence of this the French army had very much a secondary role in the sweeping withdrawal and subsequent offensive of that year. Far fewer French officers saw General Monash’s coordinated use of air power, artillery and armour that smashed the Kaiser’s armies, resulting in what Ludendorff called ‘the Black Day of the German Army’, than experienced the inferno of Verdun. Post war military planners approached the problem of France’s defence by asking the question ‘how can France fight another Verdun?’ instead of ‘how can France best defend herself?’ The difference is significant; they were asking the wrong question and consequently they came up with the wrong answer. This was reinforced by the report produced by the French army’s commission into the conduct of the war.

It has long been accepted that ‘to defend everywhere, is to defend nowhere’; if you spread your forces to defend the full length of your line you will be spread so thin that the enemy will be able to defeat you wherever he chooses to attack. This goes back at least as far as Sun Tzu (500 BC). In the nineteen twenties the French army turned this on its head. In an atmosphere where people used terms such as defending ‘every square metre’ of ‘the sacred soil of France’ not as romantic flourishes, but as serious military doctrine, the Ecole Militaire adopted a strategy known as the Continuous Line; there would literally be a continuous line of French troops running all the way from the English Channel to the Swiss Alps and on to the Mediterranean Sea. This line was to be held everywhere and at all costs. The motto of Verdun, ‘Ils ne passeront pas!’ became the military doctrine of the Third republic. (‘They shall not pass!’ credited to Petain, was actually said by General Nivelle.) There were a few lonely voices within the professional army that argued against the continuous line, but when people talk seriously about sacred soil, logic and reason don’t stand a chance.

The planning for the defences that came out of this concept took seven years and resulted in the design that was approved by the French parliament on 4 January, 1930. The resulting defences covered 140 kilometres of the Franco-German border in strength, concentrating mostly on two potential invasion routes; one blocking an attack towards Metz and Nancy and the other defending lower Alsace. This was the route taken by the Prussian armies of 1870 but they were not the traditional, nor the easiest roads to Paris. Invading via Metz meant crossing the Moselle, then the hill line behind, followed by the Meuse followed by a ridge, then the Marne and another ridge line. The easy route lay further north, through Belgium; Clausewitz’s ‘pit of the French stomach’. For centuries armies invading France had gone via the Belgian plains, where the ground was easy and flat and there were no major river obstacles or ridge lines all the way to Paris. Bismarck had avoided Belgium in 1870 to avoid upsetting the British, in 1914 the Kaiser and Moltke had not been concerned by the issue and after that it was no longer an issue, the battle ground would be Belgium. At the first sign of a threat from Germany the plan was for a French army to advance into Belgium and dig in alongside the Belgian army, providing further manpower to defend the major Belgian fortifications and to occupy the ground between them. In the immediate post-war period this had been expected to be an Anglo-French army with the British providing something close to the fifty divisions they’d had by the later stages of the First World War, but by 1930 the British army had only two divisions available to send to the continent with anything under a year’s notice and the French had to be entirely self-reliant.

Belgium only withdrew from their alliance and reverted to neutrality in 1936 following the German re-militarisation of the Rhineland, when France’s inaction was seen by the Belgians as evidence that the French were unreliable allies. Even then the French plan was to advance into Belgium and dig in before the German’s attacked. Hopefully the Belgians would see reason and a invite the French armies in well before the Germans were ready, allowing the French time to properly prepare their defences. This was still the plan when war broke out in 1939; the British and French requested permission to take up defensive positions in Belgium and were refused, it was only after Germany had attacked that the Anglo-French armies were allowed to cross into Belgium.

The Maginot Line was not the continuous line of reinforced concrete emplacements that the Line would suggest, but a series of forts in key defensive positions. These forts were vulnerable to infiltration by infantry, just as the forts at Verdun had been. This fault meant that in 1940 when the Germans attacked France, while ten divisions were based inside the Maginot defences, a further thirty divisions were stationed between the Maginot fortifications. These Interval Troops, in trench lines identical to those of 1918, were there to defend the impregnable Maginot Line! Had the fortifications been continued, and been built along the same lines as the main Maginot Line defences they would not have stopped the Germans, they would have just further immobilised the French army and allowed the Germans the opportunity to attack as and when they desired and with whatever forces they deemed necessary. We know this to be the case because that is exactly what they did; the German 16th Army attacked the Maginot Line southeast of Sedan on 19 May 1940 (three weeks before Paris fell). This was intended to be no more than a feint, designed to grab the French command’s attention and prevent them withdrawing forces from the Maginot Line to feed into the critical battle in the north. Instead the Germans succeeded beyond their expectations and took the fort in a single day. The result was that while the allied armies were fighting for their lives in Belgium and German Panzers were racing towards the English Channel, the French army was actually feeding more troops into the prison camp that was the Maginot Line.

The other fort to consider when contemplating how the Maginot Line would have performed had it been extended all the way to the English Channel is Eban-Emael. When it was completed in 1935 Eban-Emael it was the largest, most modern, and considered to be the most impregnable fortress in the world. When the Germans attacked it on the 10th of May 1940 they were able to disable the fortress’s armaments in a matter of minutes, rendering Eben-Enael harmless and the Belgian garrison surrendered the next day.

The Maginot Line, far from helping the French defence, actually severely hindered it. In 1940 the French army was desperately short of artillery and critically short of anti-aircraft guns, but priority was given to equipping the fortifications of the line rather than the mobile divisions that would fight the battle in the north; so those forces that would have to advance up the route considered most likely to be used by the Germans were given a lower priority than the least important, least vulnerable and least likely to be attacked section of the Maginot Line. Infantry divisions that would march along exposed Belgian highways, and armoured divisions that would try to block the Panzer breakthrough, were all left completely exposed to the Stukas so that garrison troops under five metres of reinforced concrete could feel a little more secure.

Worse than the material drain that the Maginot Line posed, which was bad enough, there was the mental barrier that it presented to the thinking of the French political and military leadership. The Ecole Militaire was completely indifferent to advances in armoured doctrine and technology because, after all, they were secure behind the fortifications of the Maginot Line. And if the military commanders were less than keen to have an armoured force, their political paymasters were even more reluctant to go to the expense of an armoured corps after they’d payed for the enormous expense of The Line, which had gone well over budget, and which they’d been assured would guarantee the security of France for at least a generation. French suffered from the same mentality that knights in a besieged medieval castle had, they were reluctant to advance out from behind the safety of their walls.

From the moment the Maginot Line was completed, the French give up the option of making the first move against Germany. When Hitler tore up the Treaty of Versailles and sent his small army into the Rhineland, rather than send their far larger standing army to drive him out, which probably would have resulted in the collapse of the Nazi regime there and then, the French did nothing. This decision cost them enormously in credibility and led to the collapse of their alliance with the Belgians, the very alliance that had been considered critical in the design of the Maginot Line. They then continued to sit immobile while Hitler rearmed and proceeded to swallow up the small countries of central Europe. When war finally came, during the period of the Phony War, when the French were desperately short of information concerning German intentions in the west and urgently needed to know where the Schwerpunkt of the German attack would fall, the French air force, after the loss of only four reconnaissance aircraft over the Rhineland, forbade any further flights beyond the forward edge of French ground forces; so an air force with 400 reconnaissance aircraft might as well have had none and an army was essentially blinded not by the enemy, but by its own feeling of security.

Reference Material:

To Lose a Battle: France 1940 by Alister Horne.

Dunkirk: Retreat to Victory by Major General Julian Thompson.

England’s Last War Against France: Fighting Vichy 1940 -1942 by Colin Smith.

Blitzkrieg by Len Deighton.

Blood Tears and Folly by Len Deighton.

 

[corditeman]

An excellent evaluation, Mr. Cook...

The Maginot Line had the same 'unsinkable' attitude as the 'RMS Titanic', and maybe similarly it was the level of investment - 'If it costs so m uch, it must be the best' - which influenced French thinking.

Britain planned as late as June 1939 to increase munitions production to the same levels as were needed for the Western Front. The Dalbeattie cordite works and other explosives production sites in South West Scotland were for a Western Front that never materialised. By 1942 the works were virtually on care and maintenance and munitions were shipped in from the USA and Canada.

 

[BlondieBC]

...

The thinking behind the Maginot Line was quite obviously a product of France’s experiences of the First World War. More specifically, it was based of the French army’s experience of the battle of Verdun. More French officers rotated through the battle of Verdun than any other battle of the war and while the French army did not break at Verdun, it was severely damaged by the battle. So much so that by 1918 it was the British army that was the principle attacking force on the allied side, not the French. As a consequence of this the French army had very much a secondary role in the sweeping withdrawal and subsequent offensive of that year. Far fewer French officers saw General Monash’s coordinated use of air power, artillery and armour that smashed the Kaiser’s armies, resulting in what Ludendorff called ‘the Black Day of the German Army’, than experienced the inferno of Verdun. Post war military planners approached the problem of France’s defence by asking the question ‘how can France fight another Verdun?’ instead of ‘how can France best defend herself?’ The difference is significant; they were asking the wrong question and consequently they came up with the wrong answer. This was reinforced by the report produced by the French army’s commission into the conduct of the war.

It has long been accepted that ‘to defend everywhere, is to defend nowhere’; if you spread your forces to defend the full length of your line you will be spread so thin that the enemy will be able to defeat you wherever he chooses to attack. This goes back at least as far as Sun Tzu (500 BC). In the nineteen twenties the French army turned this on its head. In an atmosphere where people used terms such as defending ‘every square metre’ of ‘the sacred soil of France’ not as romantic flourishes, but as serious military doctrine, the Ecole Militaire adopted a strategy known as the Continuous Line; there would literally be a continuous line of French troops running all the way from the English Channel to the Swiss Alps and on to the Mediterranean Sea. This line was to be held everywhere and at all costs. The motto of Verdun, ‘Ils ne passeront pas!’ became the military doctrine of the Third republic. (‘They shall not pass!’ credited to Petain, was actually said by General Nivelle.) There were a few lonely voices within the professional army that argued against the continuous line, but when people talk seriously about sacred soil, logic and reason don’t stand a chance.

The planning for the defences that came out of this concept took seven years and resulted in the design that was approved by the French parliament on 4 January, 1930. The resulting defences covered 140 kilometres of the Franco-German border in strength, concentrating mostly on two potential invasion routes; one blocking an attack towards Metz and Nancy and the other defending lower Alsace. This was the route taken by the Prussian armies of 1870 but they were not the traditional, nor the easiest roads to Paris. Invading via Metz meant crossing the Moselle, then the hill line behind, followed by the Meuse followed by a ridge, then the Marne and another ridge line. The easy route lay further north, through Belgium; Clausewitz’s ‘pit of the French stomach’. For centuries armies invading France had gone via the Belgian plains, where the ground was easy and flat and there were no major river obstacles or ridge lines all the way to Paris. Bismarck had avoided Belgium in 1870 to avoid upsetting the British, in 1914 the Kaiser and Moltke had not been concerned by the issue and after that it was no longer an issue, the battle ground would be Belgium. At the first sign of a threat from Germany the plan was for a French army to advance into Belgium and dig in alongside the Belgian army, providing further manpower to defend the major Belgian fortifications and to occupy the ground between them. In the immediate post-war period this had been expected to be an Anglo-French army with the British providing something close to the fifty divisions they’d had by the later stages of the First World War, but by 1930 the British army had only two divisions available to send to the continent with anything under a year’s notice and the French had to be entirely self-reliant.

Great summary.

It is interesting to not that DeGaulle and some of the other advocates of more mobile war were advisers in the Polish/Russian Wars where they saw a much more mobile face of warfare. Another interesting note is even the biggest advance on the Western Front pale in to comparison to the moves on the eastern front.

The secondary point you make is the most important point, namely the French assumed a level of support from Britain that simply did not exists. From the time of the ToV to the Fall of France in 1940, France tended to assume that the UK would provide many extra division if needed that the British simply refused to fund. Without the British support, France should have chose a soft peace with Germany. In the mid 1920's when it is even more clear the UK will not help, it should have found a way to make a lasting peace instead of a punitive peace. By the 1930's France had a terrible dilemma, yes it could have overthrown the Nazi, but then it would need to occupy Germany which it could not afford to do. And if the right wing of German politics is broken, it means the communist win, and a when the Red German Army crosses the Rhine, it will never leave.

Without Russia as a strong Ally, France was simply fighting about its weight class when it fought Germany after 1866.

Now this

 

[Dan Reilly The Great]

So basically it was just one of those things. A serious case of stuff happening, nothing anyone could really do.

On the contrary, there was PLENTY that could be done. It was just that the Allies didn't do it.

They could have launched a full scale assault into Germany while the bulk of the Heer was busy in poland(in fact this was exactly what they said they would do), they did not. The Belgians could have allowed the Allies to move into Belgium to shore up their defenses against the almost inevitable German attack, they chose to wait until it was too late. They could have chosen to pay more attention to the reports of German troops moving through the Ardennes, they largely ignored them.

The Maginot line could have been used to allow the Allies to conduct offensive operations in Germany with little fear of a flanking attack on France proper, thus taking the initiative and forcing the Germans to dance to their tune, unfortunately the Allies chose to ignore centuries of siege warfare and assume that simply sitting behind your walls will be all you have to do, ignoring the fact that the best way to lift a siege is to relieve it from the outside with a mobile army.