Adolf Hitler and General Wilhelm Keitel inspecting the Maginot Line, France, 1940. France built the system of fortifications in the 1930s to protect its eastern frontier from invasion. But in 1940, the Germans simply bypassed the supposedly impregnable line, entered France through the Ardennes, a strategy disregarded by the French due to their belief that the terrain would be impassable for German tanks. The photographer is unknown.