Even after World War I had ended the French elite were still wary of the threat from the East, despite the Treaty of Versailles stripping away most of Germany’s power. As a result of these fears they constructed huge defences over their eastern border from Luxembourg in the north to Switzerland in the south. Filled with heavy weapons instalments, the defences were designed to be almost impenetrable to any advancing German force. They were designed by Andre Maginot and built for a cost of about 3 billion French francs.
The huge cost of the defences led to other areas of the French military being poorly financed and, although the Maginot Line did stop a direct German attack the Nazis simply invaded though Belgium in 1940 and thus avoided most of the defences. The French had left their Belgian border sparsely defended, so the Germans outflanked the line, blitzing through the Ardennes. When Allied forces invaded France in 1944 they too mostly bypassed the wall, further highlighting what an expensive mistake it was.
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