The French Minister of Defense, Andre Maginot, built the line between 1928 and 1939. It was a system of some 600 major fixed fortifications and 5,000 blockhouses or firing positions, covering the French-German border between Switzerland and Luxembourg. It was intended to impede any German attack for 2-3 weeks to allow mobilization of the French Army. This concept was based on the faulty assumptions of septuagenarian French generals and politicians who had little grasp of mobile warfare. In 1940 the Germans, commanded by generals in their 40s and 50s, attacked through lightly fortified Belgium, entering France in 5 days.