The Maginot Line
Schoenenbourg was a large arrangement of bunkers with 600 soldiers. The six bunkers were separated from their supporting facilities with barracks, a kitchen, a sick bay, and a power station. The parts were connected 18 to 30 meters below ground via a tunnel system that measured three kilometers.
However, because it was so expensive to set up the bunkers in Alsace, other parts of the line were neglected. The facilities were only intended to defend against infantry attacks; tank and aerial assaults were not taken into consideration.
In 1940, German troops attacked the Netherlands and Belgium, and could therefore circumvent the Maginot Line to the north. The German army used tanks to break through a weak line of defence in the Ardennes. German soldiers pushed forward to the French coastline to the English Channel, and in this way were able to trap Allied units in the first phase of the offensive.