Forts stand aboveground, flanked by pillboxes and barbed-wire entanglements.
Underground chambers provide space for communications systems, hospitals, storerooms, garages, and living quarters for officers and men. In May 1940, the Germans invaded France through Belgium, passing north of the Maginot Line. In three weeks, they swept past and then behind the line, and captured it from the rear. The Maginot Line was overhauled in the 1950's for possible use in case of atomic war. See also Siegfried Line .