Fortified Position of Liège

The fortified position of Liège was established following World War I by Belgium to block the traditional invasion corridor from Germany through Belgium to France. The Belgian experience of World War I, in which the Belgian Army held up the invading force for a week at Liège, impeding the German timetable for the conquest of France, caused Belgium to consider a refined defence strategy. Belgium upgraded the existing fortifications of Liège and extended them onto the Herve plateau closer to Germany, using the most advanced fortifications available to Belgian military technology. However, in 1936, Belgium's neutrality was proclaimed by King Leopold III of Belgium in a vain attempt to forestall another conflict, preventing France from being able to make active use of the Belgian defences and territory in the forward defence of France. At the outbreak of World War II, Belgium's defences had to resist alone until France could advance into Belgium after neutrality failed. Again the fortifications could not hold the Germans.

The position fortifiée de Liège was divided into the modern defensive line, anchored on the Albert Canal by Fort Eben-Emael and extending to the south through a planned five additional forts, designated PFL I, and the ring of forts around Liège itself. Liège commanded crucial road and rail crossings of the Meuse, and remained as strategically important in the 1930s as in 1914. The modernized Liège forts were designated PFL II.

The first modern forts at Liège were built between 1888 and 1891 at the initiative of Belgian General Henri Alexis Brialmont. The forts made a belt around Liège at a distance of about 7 kilometres (4.3 mi) from the city centre. Following the Franco-Prussian War, both Germany and France had extensively fortified their new frontiers in Alsace and Lorraine. Belgium's comparatively undefended Meuse valley provided an attractive alternative route for forces seeking invade either France or Germany. The plains of Flanders could provide transportation, food and fuel for an invading force. Brialmont recognized that France and Germany would once again go to war. Fortifications at Liège and Namur might dissuade France and Germany from fighting their next war in Belgium. The Liège fortifications were intended to deter Germany, while the Namur forts were to dissuade the French.

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