What If The Maginot Line Had Been Built Along The Franco-Belgian Border?

Having read a collection of interviews with politicians and ambassadors conducted 1933-43 by W.P. Crozier the editor of 'Manchester Guardian' I have been provoked into writing a number of counter-factual postings about that period. Most of them I had thought of before, but reading that at least one leading man on the political scene at the period considered these developments to be feasible added weight to me writing about them.


This posting was one I had considered myself when looking at the alternatives around the French and British resisting the German invasion of France in 1940. I found this speculation reinforced in an interview between Crozier and Leslie Hore-Belisha, secretary of state for war 1937-40. Speaking in either November or December 1939, Hore-Belisha advised that France should be encouraged to extend the Maginot Line to run along the Franco-Belgian border (and in fact the Franco-Luxembourg border too). Of course, only 5-6 months before the Germans invaded France it would have been too late to put effective defences in place, though when the British Expeditionary Force landed in France in September 1939 they worked with the French to extend defences from the end of the line East of the border with Luxembourg right to the Channel coast. However, the option of the line running along the borders of Luxembourg and Belgium could have been implemented when the Maginot Line was originally constructed from 1930 onwards.

The Maginot Line is named after was André Maginot, French Minister of War 1922-4 and 1928-31. The line was in fact a long, sometimes patchy, chain of defensive fortifications stretching 20-25Km deep, running the length of the Franco-German border with a similar scheme along the Franco-Italian border known as the Alpine Line. It had forward border posts often disguised as houses where troops would detect invasion and seek to slow up the advance, particularly of tanks, using emplaced explosives. There were 17 fortified observation posts on hilltops providing good views of the landscape with high quality optics. They were equipped both with telephones to the fortresses and wireless transmitters.


About 5Km behind the border posts were 5000 block houses of the Outpost and Supply Line, again focused on stopping the advance of tanks and allowing the troops of the main Ouvrage line to prepare. Ten kilometres back from the border was the Principal Line of Defence, six lines of anti-tank obstacles and a line of anti-personnel obstacles with gates that could be moved to block roads. Behind this line were the 352 infantry casemates equipped with crews of 20-30 with two mounted machine guns and an anti-tank gun. In this zone, about 0.5-1Km behind the Principal Line of Defence were 78 Infantry Reserve Shelters equipped with their own electricity and accommodation for 200-250 soldiers. These were to be used to halt any advance against the Principal Line of Defence and act as headquarters for counter-attacks against the presumably stalled invaders.

The infantry casemates were reinforced by the 97 ‘Petit Ouvrages’ which were a series of connected infantry bunkers with their own accommodation, generators, hospital units and stores. They were connected by a tunnel network and housed 100-200 soldiers. The 142 full-scale Ouvrages were self-contained fortresses with heavy armament and units of 500-1000 soldiers. The Ouvrages had Safety Quarters in their proximity, basically barracks to allow soldiers to get to the Ouvrages easily in case of a surprise attack. The Ouvrages were connected by an underground narrow gauge railway stretching to supply depots up to 50 Km back. Over 100 Km of tunnels connected the various fortifications. In addition to generators in the casements, shelters and various ouvrages, the Ouvrages themselves were connected to the national electricity grid by underground cables and two separate telephone lines ran between all the various fortifications.


In particular areas there were Flood Zones which along the lines of the Dutch plans for defence, could be deliberately flooded to slow up the invaders’ advance. Behind the Maginot Line, heavy railway artillery was deployed with a longer range than the 10-12 Km of the fortresses’ guns.


As France and Belgium were allies 1920-36, the French did not build the line along the Franco-Belgian border and the idea was that the French forces would move to support Belgium, which is in fact what happened in 1940. However, following the remilitarisation of the Rhineland in 1936, which France could have contested, as I have discussed before on this blog, Belgium broke the alliance and became neutral. The Belgians vacillated 1936-40 and on the eve of the German invasion seemed almost ready to let the Germans into the country without fighting back; the Belgian King Leopold III did not flee Belgium in the way other monarchs did when their country was invaded in order to carry on the fight from Britain and he oversaw Belgium’s surrender.

Following the end of the Franco-Belgian alliance, France did take steps to fortify along the mutual border, but far weaker than the construction farther South. Part of the problem was the low lying nature of this region compared to Alsace-Lorraine and the high water table which meant a risk of flooding of the extensive tunnel systems. Even by 1936 the enthusiasm of 1930 seemed to have waned and so the necessary funds to overcome this problem were not as forthcoming. However, other approaches such as the mobile defensive tactics favoured by De Gaulle and Paul Reynaud were not introduced even in combination with the weaker defences along the Franco-Belgian border. As noted above more impetus was put into strengthening the line in this region when the BEF arrived in 1939, but by then it was too late.


The Maginot Line is seen to sum up the flawed mentality of the elites in French society in the inter-war period. This includes a very defensive mentality, seen as stemming from the experience of the First World War that Maginot and many others in the government and military had seen first hand. It can be argued that the whole idea of the Maginot Line was based on the experience of the battles for the fortresses of Verdun, February-December 1916 which sucked in so many German troops in trying to seize it that it did have an impact on the German Army. Ultimately the death toll was 163,000 French to 143,000 German but it did distract units from other parts of the front and did not lead to significant German progress despite 11 months of fighting. Interestingly General Nivelle’s 1916 slogan of not letting the enemy pass was taken up by the units who staffed the Maginot Line.


Certainly the Maginot Line defences look like what had been seen as sophisticated in 1918 taken the next level. Both sides on the Western Front, but especially the Germans had developed extensive bunkers and other fortifications to a degree that they resembled 20th century castles, able to withstand ‘siege’ even when assaulted by high explosives. Similarly the inclusion of the narrow gauge railway mimicked what had been developed behind the front line during the First World War. Perhaps more importantly the Maginot Line seems to be an embodiment of the perception of the French elites that they were under siege from not only the renascent Germany even before Hitler’s rearmament, but also from extremists within France. William Shirer’s account of the final two decades of the Third Republic shows the paralysis which gripped so much policy in this period and among many in French society somehow a desire for victimhood, that rebirth of the ‘proper’ France could only come from defeat; a line which the Vichy regime in fact took following the defeat of 1940. The obsession with ‘sitting tight’ within France and not taking active steps was shown by the pathetic ‘invasion’ of Germany by French forces September-November 1939. It seems that there was almost a fear of potential victory and given how debased many elites in France saw republican society I guess this is no surprise, they certainly would not such a society and political situation re-invigorated by even the mildest of victories against Germany.


Whilst one can certainly argue for the Maginot Line manifesting a broad ‘Maginot mentality’, the perception that the Line itself had the nature it did because French commanders and politicians did not understand the nature of mechanised warfare and were easily caught out by the German blitzkrieg in 1940 is only partly accurate. It must be remembered how unreliable most tanks had proven during the First World War and that Britain with its combination of tanks and infantry had made best use of them especially when compared to the Germans who at best had created over-engineered tanks that added nothing and in their complexity caused errors; to a degree, an error Hitler’s designs for tanks in the latter half of the Second World War were to repeat. If we look at the tanks that were used by the Germans in 1940 the bulk were Panzer Is and IIs which could have easily been halted by decent French infantry units let alone French tanks which at that stage were superior to the average German tank. The German forces would have been weaker still if they had not been able to draw a third of their stock from the Skoda works in Bohemia. Another assumption is that the invasion of France followed the plans that the Germans had laid out. In fact, certainly the rapid penetration of tank units into France was often done purely on the initiative of unit commanders at times against the wishes of their superiors. If German tank generals had been more obedient then blitzkrieg would not have looked as effective (or as risky) as it proved to be.


The Maginot Line can be seen as only enhancing First World War technology rather than engaging with that to be found in warfare as it was anticipated to be in the 1940s,even though the invasions of Poland, Denmark and Norway cannot really be classified as blitzkrieg, partly due to the terrain. However, the approach of the defence in depth aimed at slowing up an advance through the need to penetrate levels of defence, combined with the combination of a unified network which retained autonomy (for example, an Ouvrage was able to shell another Ouvrage in the line if it had been over-run by invaders) was a sound static response to tank warfare. In addition the deployment of the heavy artillery on railways gave the opportunities for a flexible response in case of break-throughs in the line. What was missing was the mechanised units with sufficient weight of tanks to snuff out salients that would develop once a breach had been made. This would have been a weakness defending the Maginot Line as it was in defending Belgium and northern France without such defence.


One interesting point to note is that one reason for not building the Maginot Line along France’s border with Belgium was the sense that it could inhibit the planned French intervention in Belgium. You then must ask why during the period of the Franco-Belgium alliance, six years of which coincided with the construction of the Maginot Line no attempts were made to build a line along the Belgian-German border. Of course there were defences but as the fall of the flat-roofed fortress of Eben-Emael showed such fortifications could be captured. In addition, simply having a defensive line does not mean there cannot be offensive moves. In fact such attacks have the advantage of the artillery barrage behind them. In many ways Ouvrages especially if built up would have been more powerful in the flatter lands of northern France and Belgium, because as the First World War had shown even controlling a low ridge in such territory could allow you to dominate a battlefield and be unassailable without heavy loss. 


Paratroopers could have overcome such challenges especially if the French lacked the mobile forces behind the frontline to snuff out paratroop assaults. However, as shown on Crete and at Arnhem, with speedy concentrated action it was feasible to eliminate such attacks. The British Army was one of the most motorised forces in the war at the time and would have been suitable for such a role if anyone on the Allied side had felt it was appropriate. In addition, stalling the German forces at the Belgian border would have opened up the chance for shelling from Royal Navy battleships and potentially from an amphibious flanking attack by British forces along the Belgian coast. Either of these actions would have had the benefit of the longer Maginot Line's guns to provide support.


Whilst the Maginot Line may have used the best technology of the First World War, its location was rooted in the Franco-Prussian War of 1870-1. That had been the last time that the Germans had invaded into Alsace-Lorraine. In 1914 when these provinces were in German hands the French made a tentative attack, Plan XVII into these regions, where the Germans were able to resist. The main German attack in 1914 as in 1940 came via Belgium. In 1940 forces came through the Ardennes mountains of southern Belgium which had deemed by the French to be impassable for armies. This is despite France and Belgium being allies for 16 years and having been able to make military manoeuvres in the region. Whilst the exact focus was different between 1914 and 1940 in both cases the Germans came across the Belgian border into northern France. In 1914 it was the ability to move French armies quickly as the Germans approached Paris, just the fast mobility that Reynaud and De Gaulle sought in the 1930s, that had saved France with 'The Miracle of the Marne'. Yet the lesson was not learnt from that success nor was a lesson learnt from the direction of the 1914 invasion. It was appropriate to defend the industry of Alsace-Lorraine, but what about the industry of the Nord-Pas-de-Calais which was quickly swept up by the German invasion of 1940?


The failure to anticipate that, as in 1914, the Germans would come through Belgium and in the 1930s to have tested whether the Ardennes were the natural defence it was assumed, made the Maginot Line, even as it existed by June 1940, immediately obsolete. The Maginot Line held 36 divisions in 1940, a third of the French Army they faced 19 divisions of the Wehrmacht along their front. The ouvrages around Mauberge were effectively outflanked when the weaker defences along the Belgian border were overrun. Interesting the first break-through of the Maginot Line did not occur until 15th June, the day Paris fell to the Germans. The break through owed much to the rout of many French units which characterised the German advance into France. Weak sections such as at the Vosges could be broken, but in contrast the line at Wissembourg held. Part of the problem of the Maginot Line was in certain areas such as the Vosges, where there were only observation posts to summon forces rather than fortresses and along the Rhine, there was an over-dependences on the uplands and the river to do the work of defence for the French. This severely weakened the line and it was particularly in these areas that the Germans were able to penetrate.


Despite the flaws, the bulk of the ouvrages even those attacked from the rear held out and it was only the armistice signed on 22nd June which ended their defiance. The value of such modern fortresses was revealed again to be effective in 1944-5. This time the bulk of French ports, places like St. Nazaire, La Rochelle and Lorient held out under German occupation until May 1945 despite the liberation of Paris in August 1944. The Germans were as great fortress builders as the French as can still be seen along many locations on the French coast.


Let us assume, that perhaps France and Belgium could not come to an agreement in 1920 and the ambivalence between them seen after 1936 was apparent through the 1920s too. In such a context the expansion of the Maginot Line along the Belgian border would have been feasible. Given the innovation, such as the pop-up turrets that the Maginot Line introduced, it seems unlikely that French engineers would have been unable to resolve the issues of constructing defences along the Belgian border, after this was a region in which French military engineers had gained a great deal of experience 1914-18 and as can be seen even today sophisticated structures were constructed if predominantly on the German side. The Belgians may have felt uncomfortable with such defences along the border, but there is little they could do about it. In addition the Maginot Line was not like the Berlin Wall and the other border defences that were to separate the Communist bloc states from West Germany and Austria. Traffic still flowed across the Franco-German border before the outbreak of war. In addition, even though the French invasion of Germany in 1939 was pathetic it was in no way inhibited by the presence of the Maginot Line. So, an expansion of the line along the Belgian and Luxembourg borders with France would not have prevented French and particularly British forces penetrating into Belgium if this had been seen to be appropriate.


The border of France with Luxembourg is 73Km and France with Belgium 620Km compared to 450Km bordering with Germany; there was also a stretch of Maginot Line along the northern border of Switzerland. Thus, ironically the defence along the Belgian border would have been greater in length than that around Alsace-Lorraine. Given the way in which the Vosges was treated it seems likely that the line face the Ardennes would have been left weak too. This would have undermined the whole defence and it can easily be argued that despite the sophistication of the defences and the 3 billion Francs spent even on the Maginot Line we know, it was insufficient. Whilst a longer Maginot Line would have been a heavy burden on the French government expenditure it would have formed an even greater public works project and as rearmament in Germany reduced unemployment, work on the greater Maginot Line would have made an even larger contribution to stimulating the French economy through the workers it employed and the incomes they could spend. Notably it was a form of regional redevelopment that in our world brought benefit to the peripheral regions of the Alsace-Lorraine and Alpine France but could have brought this into the northern regions of France with their urban industrial areas that had suffered both between 1914-1918 and the Depression of the 1930s.


Of course, if the Ardennes had been weakly defended it would have formed an very narrow channel through which if not as impassable as the French had assumed, was far harder to progress through than the flat roads farther North. In fact the traffic jams of German military vehicles trying to get through in 1940 put them at immense risk. If the French bomber force had not been so dispersed and used so ineffectually, the attack through the Ardennes could have been easily stymied. Even observation posts and heavy artillery on railways behind the French frontier with the Ardennes let alone some ouvrages, would have severely delayed any advance this way.


The Maginot Line was never envisaged as blocking an advance entirely, simply slowing it up by 2-3 weeks to permit full mobilisation of France's forces. It was well designed in those regions with ouvrages for severely slowing the advance of tanks. This would have certainly have fouled up blitzkrieg. Much of the German victory in France came from the success of the speed of the advance in terrifying not only the French population but vital units of the French Army who fled South to avoid being surrounded. Interestingly the troops of the Maginot Line generally did not flee. Thus, we can easily envisage that British and French forces have advanced from behind the Maginot Line into Belgium but have been repelled and flee back behind the defences. This gives them breathing space to regroup and reinforce those units held in the Line's fortresses. Being much longer than in our world, perhaps as much as half of the French regular army is housed in these frontier fortresses.


The first difference is that unless Maginot Line fortresses surrendered, and the evidence suggests that even when surrounded they did not, then blitzkrieg would have ground to a halt. In some ways the situation would have been like the Lines of the Torres Vedras used by General Wellington during the Peninsular War, defences outside Lisbon against which French forces failed to penetrate and ultimately were compelled to withdraw. With modern supply lines the Germans would not have done that but all the tanks that had rushed from Germany would have ended up sitting in a killing zone pummelled by the guns of the ouvrages, the railway artillery behind and the bombers that the Germans could put into service. Of course, the Germans would not be passive and would use paratroopers and bombing raids to try to smash through. Break-throughs are likely to have been more narrow than happened when France was invaded in 1940 and would resemble much more those from the 1914-18 conflict. The question remains whether the French and British would be ready to react quickly enough to snuff out salients and paratrooper landings. Quite possibly given much of the disorder shown in 1940 in the face of the German invasion they might not have been able to do so. 


Whilst blitzkrieg was an effective approach to waging war especially in western Europe, the belief in the power of blitzkrieg can be seen as having been more effective. The collapse of French forces so quickly in 1940 emphasises this. The over-stretched break-throughs could have been cut off if there had been a calm, organised response that proved to be lacking. In contrast as the experience of Maginot Line fortresses proved, engaging with the conflict on the basis that the French had developed to a high art by 1940, would have entirely shifted the balance. Yet, just where such a situation was needed, along the Belgian border it was largely lacking.


Ultimately the Maginot Line running along the Luxembourg and Belgium borders probably would not have prevented the conquest of France, but it would have altered the subsequent course of the war a great deal. Rather than those who felt that it had been a mistake to fight the Germans coming to the fore as they did both in occupied France and the Vichy regime area, there would have been greater pride that at least the advance had been halted and the time it bought would have been recognised as important. This would have meant a different attitude in the period 1940-45, especially when options such as the government relocating to Algeria were being considered in 1940. It would certainly have had an impact on the retreat of the BEF. At best the Germans would have penetrated through narrow slots and would not have had the opportunity to surround the British as effectively, particularly with islands of resistance in the ouvrages still held by the French. This would have allowed a more effective retreat by French forces and probably by the British so not leading to the abandonment of heavy weapons at Dunkirk, rather these being taken off in a more orderly way, perhaps from Le Havre, Cherbourg or Brest.


The biggest impact would have been on German war materiel. The tanks which invaded France were not the best quality, but the men inside them would go on later in the war to be among those who invaded the USSR and fought in North Africa, notably Rommel. If they had died in large numbers butting against the Maginot Line, the Germans would have been far less well staffed and equipped for their battles into those two theatres. Of course, the relative success of the Maginot Line may have led to faulty conclusions being drawn about the value of powerful static defences. Such an approach was impossible in the vast spaces of the USSR but maybe the British in Egypt would have moved to creating some kind of fortress line rather than engaging with mobile warfare to counteract the German advances in North Africa.


Unless the Franco-British response to paratroop drops behind the Maginot Line on the Belgian border had been entirely ineffectual, and of course there was a chance that they might have been, Hitler may have come to disregard the use of paratroopers as in our world he was to do following the invasion of Crete in 1941. The British learnt a very different lesson from Crete and ramped up the use of paratroops notably on Sicily, Arnhem and for D-Day, really only in the latter case can they be deemed to have succeeded. With the failure of German paratroopers to continue the success they had had in the Netherlands and Belgium once they came to trying to break the Maginot Line, subsequent uses, most notably on Crete may have never occurred. The attack on Crete might have been restricted to a seaborne invasion and this may have favoured a more successful defence by Greek and British forces.


When looking at the role of the Maginot Line in the history of the Second World War one cannot detach it from the difficulties with the mentality of the French elites in the 1930s. No defensive fortifications or tactics could work without the political will to make them work. Without such political will it would be unsurprising if, as happened in 1940, many ordinary soldiers could see no point in trying to put the tactics into effect. What is interesting is whilst the Maginot mentality seemed to hamper French commanders and politicians reflecting on different options for defending the country and ignoring those advocating a mobile defence based on tank units, the mentality did foster and esprit de corps among those manning the Maginot Line which meant morale remained higher and the units far more effective than among the standard infantry. The problem was that these units generally were not put to the test as they were by-passed and the armistice signed before most of them had faced combat.


Overall, whilst a greater Maginot Line may not have saved France from invasion, it certainly would have blunted the German advance providing opportunities both for the French and British. The slowing of the advance and the time and resources that the Germans would have had to expend to break the line would have been lost to Germany in terms of its subsequent battles and the war would have definitely unfolded differently.