As I understand it, the Maginot Line (intended to protect Frace from invasion from Germany) was never built along the Belgian border. This was because French defense planners saw the French Army as allied with the Belgian Army, and the frontier did not need a defensive line. So, the very advanced Maginot line only protected the Alsace Frontier.
My question: had the line covered the entire northern border, would this have prevented a German attack? True, fixed defenses were passe, but having a defensive point in their rear would have worried the German generals.
Any ideas?
The Line was also a failure because it failed to cover the Ardennes Forest, which the French military planners considered impassable, not anticipating developments in light-tank technology.
Not really. The French military would have wanted it to be extended along the Belgian border too. It wasn’t done for diplomatic reasons (Belgium didn’t like the concept, since it meant that the French army would likely defends its borders and abandon Belgium in case of German attack) and for budgetary reasons.
Leaving a defensive point in their rear wouldn’t have worried them. Actually, they did exactly that. Isolated fixed defences couldn’t really threaten them. The problem with the Maginot line (from the German point of view) was its very real defensive value. It was a formidable uninterrupted line of interconnected forts ( surprisingly modern for the time if you look at pictures of the inside) and fixed defences that would have been difficult to breach with a mobile army behind it.
It likely wouldn’t have helped. A static defensive line doesn’t help if any part of it breaks, which happened very quickly in the northern part of the Line. Also, bear in mind the major blow for Allied forces wasn’t the Germans invading France through Belgium, but rather cutitng off the Allied forces IN Belgium by going through the Ardennes.
Defense in depth DOES work, as evidenced by the Battle of Kursk, when the Russian lines were used to grind down a very large German force, but if it fails in one place the result is disaster, and the Maginot Line was, in fact, breached, at Mauberge.
It’s worth noting that the Germans did take a shot at the Line and were completely repulsed.
The problem was French doctrine. By the end of WWI, the French Army was shattered and incapable of attack led by Metropolitan units. Instead, they relied on defense.
You can see it in their dispatches in 1940. The Germans crossed the stream at a certain point, but French units had sealed them in. All that remained to be done was for the Germans to attack the French lines and die on the wire.
This is laughable to our modern ears. By 1940, advances in motorization (almost universal amongst good units) and mechanization (limited to a few units) had made it too easy to bypass most defenses and mass on the others. The more mobile Germans could place overwhelming power at the critical point and break through every time.
So the French had learned the wrong lesson from the previous war. The idea of the Line was to have a ready-made WWI trench system, in an emergency it could be quickly manned while mobile units further in the rear could move by train to plug up any holes.
While the Germans certainly used the unfortified portion of the frontier as crossing points, it is unlikely the Germans could not have made three or four breakthroughs with specialized units and then confront the defense-oriented mobile columns.
I hope this helps.
I would like to add to this comment that the few German units who did attack points along the line were more often than not soundly trounced, even though the line was undermanned, and mostly by soldiers considered unfit for normal service. None of the major forts ever fell, and only a handful of “petits ouvrages” (smaller bunkers) did.
For good or worse, the line did its job - it was a deterrent, and a way to concentrate real troops up north, where the Germans were fully expected to attack, as they did in 1914. The line itself was never meant to be attacked.
As to the original question, and assuming France to have had infinite ressources (the line wasn’t exactly cheap, you know ? ;)), yes I think it could have. Or at least stalled the German advance long enough to relocate the regular army, organise muster, call for allied support… and end up with another trench war. Which the Germans would probably have won in the end, on account of superior numbers. So we’d have had a smaller Reich that would’ve lasted much longer (esp. considering the Germans wouldn’t have attacked Russia with a protracted western war on their hands).
Sometimes, losing is better 
In The Blitzkrieg Myth Mosier points out that the Maginot Line wasn’t the answer and the French never for a moment believed it was. True, Belgian sympathies made a finished line impossible, but the true purpose was one of flexible defense anyway. Of course a German break through could happen, and to answer that the French had larger tanks and more of them, it turns out they just weren’t as fast or as organized.
The French realized that their Belgian frontier was exposed. They planned around this. The purpose of the Maginot Line was to narrow the front down so the French could concentrate their forces in one area. They knew that Germany would see Belgium as an obvious route into France. The French figured the Germans would invade Belgium and the French army would advance into Belgium to meet them.
And the Maginot Line was only a one-way deterent. Once the bulk of the German Army was tied down in Belgium, French forces could cross the eastern frontier and directly attack undefended Germany.
To clear up possible confusion:
The defeat in 1940 was not caused by the Germans advancing into Belgium and the Low Countries. It was caused by everyone thinking the Germans would advance in force into Belgium and the Low Countries, where the Maginot Line was not, when the Germans actually attacked south of there.
In WWI (the first war), the Schlieffen Plan was Germany’s attack along that northern corridor. France tried to move into the central area (economically valuable mining and manufacturing) and a classic “revolving door” offensive developed (see the map in the article). The French got into deep trouble but got out of it, thanks to steely nerve on the part of one of their commanders, and the famous “taxis of Paris rushing troops to the front” sort of all-out effort.
Determined not to fall for that again, the French plan for the coming war (WWII) involved fortifying the central area and hurling their main force (and the British expeditionary force) along the northern corridor to meet the presumed German invasion head-on. But the Germans attacked at the hinge, south of the main Allied effort but north of the Maginot Line, where the French assumed armored advance was impossible because of the dense Ardennes forest. The French stationed two second-rate formations there.
As the Allies swung northeast along the corridor, the Germans punched through the hinge and turned toward the coast, cutting them off and forcing the Dunkirk evacuation.
In retrospect, tanks and mobile forces made the difference. French military doctrine was to consider the tank a mobile strong point for stiffening the infantry, and accordingly the tanks were mostly dispersed all along the front. But this was an error if the enemy concentrated.
For a grossly oversimplified example, if you have, say, 2000 tanks on each side…and one side puts them all along a 500 mile front, that’s 4 tanks in a mile width. Now let’s say the other side sneaks all 2000 of its tanks through the Ardennes and hits a one-mile section of front “stiffened” by…four tanks. That’s a 2000-4 advantage. In the words of John Keegan, when such a concentration of armor struck a weak point in the line – and by definition, any point struck by such a force would be weak – the results were certain.
How do you fight that? There’s three main ways. Firstly, defense in depth, via a series of “hedgehogs” or strongpoints that do not form a continuous line. The enemy can pass between them but leaves a force capable of cutting off its line of supply if it does. Secondly, counterattack the flanks of the penetrating column with massed armor of your own, threatening to cut it off. The French actually did have a small amount of armor available for counterattack and in fact tried exactly this; the feeble effort, unsupported by significant airpower, nearly panicked the Germans. Thirdly, you can throw everything forward in an area from which the enemy is not advancing, and try to revolving-door him in turn. Risky, and you’d probably be unable to do it unless you had already organized an advance anyway.
Thanks, **Sailboat. **Now I need to find the supporting documentation (haven’t read that part by Keegan, fristance, ETA: but its likely on the shelf) to fill in the blanks and I’ll be happy.