In 1936 Germany began building a series of defensive lines facing the borders of France and the Low countries, which was known as the Westwall to the Germans and later, to the western allies, as the Siegfried Line. It was a series or 16,000 bunkers, tank traps and tunnels some 630 km (390 miles) long, stretching from the Swiss border northward to the town of Cleve on the border of the Netherlands. The German government commissioned private construction companies to carry out the work; however, progress was slow and the quality of the workmanship varied. Following the outbreak of war in western Europe, on 3 September 1939, there was an eight-month period of inactivity known as The Phoney War. The long-awaited German attack on the western front, which began on 10 May 1940, ignored the principle of static defence lines. Armoured spearheads supported by airpower bypassed the main Maginot Line defences, attacking through the Ardennes in Belgium. Glider-borne troops destroyed the great Belgian fort at Eben Emeal and airborne troops landed behind the Netherlands defensive lines, rendering them ineffective. By the autumn of 1944 the western allies had liberated most of France, Belgium and parts of the Netherlands, and were on the German border. The Westwall/Siegfried Line was hastily refurbished but once again static defence proved incapable of stopping the allied advance.
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