After fighting the Germans in one of the most destructive wars in history for four years the French determined to make themselves less vulnerable to future German attack. One way they did this was to insist on a very harsh peace at Versailles. Another way they did this was to build enormous fortifications along the French/German border and that is what the French did.
These fortifications, named the Maginot Line after the French secretary of Defense Andre Maginot were built between 1930 and 1940 and defended France's border with Italy and Germany with concrete bunkers, tank obstacles, machine gun turrets, and artillery positions. The Maginot Line also featured an extensive tunnel system and underground railroad that would allow the French to quickly mobilize and supply their men in the event of another Germany attack.
As a defense system, the Maginot line was impressively complex. It featured over 45 large forts and 97 small forts all connected by over 100 miles of tunnel. It did have two weaknesses, however. It did not protect the border with Belgium as Belgium was a neutral country, nor did it protect the Ardennes because the French believed the the trees there were too thick for an army to pass.
Unfortunately, the Maginot line was not successful in preventing Germany from invading again. During World War II, Germany sent a decoy army to make the French believe that they were planning to attack the line head on. They then simply bypassed the Maginot Line by invading France through neutral Belgium. The Germans met some resistance, but just over a month later they had occupied Paris. In the meantime, the line still held. Even attacks on the line from behind had proved largely unsuccessful. It was not until the French government signed an armistice with Germany and ordered the army out of the fortifications that they were lost.
Some observers have criticized France over the years for almost asking for the Germans to invade through Belgium by not fortifying that section of the border. After all, the last time Germany had invaded France, during World War I, it had gone through Belgium. Why then did they think their "super-trench" would be successful in stopping another invasion? The fact is that they probably did not think that. The French realized that the Germans could easily ignore Belgium neutrality and invade through the French/Belgium border. What leaving that gap open did, however, was allow the French to concentrate most of their army in one place where they knew the Germans were likely to attack. They were still overwhelmed by the German army, but they faired better than they would have if they had been made to stretch their forces along their whole border.
