<P> The Maginot Line was impervious to most forms of attack , including aerial bombings and tank fire , and had underground railways as a backup ; it also had state - of - the - art living conditions for garrisoned troops , supplying air conditioning and eating areas for their comfort . Instead of attacking directly , the Germans invaded through the Low Countries , bypassing the Line to the north . French and British officers had anticipated this : when Germany invaded the Netherlands and Belgium , they carried out plans to form an aggressive front that cut across Belgium and connected to the Maginot Line . However , the French line was weak near the Ardennes forest . The French believed this region , with its rough terrain , would be an unlikely invasion route of German forces ; if it was traversed , it would be done at a slow rate that would allow the French time to bring up reserves and counterattack . The German Army , having reformulated their plans from a repeat of the First World War - era plan , became aware of and exploited this weak point in the French defensive front . A rapid advance through the forest and across the River Meuse encircled much of the Allied forces , resulting in a sizeable force being evacuated at Dunkirk leaving the forces to the south unable to mount an effective resistance to the German invasion of France . </P>
where was the virtually unprotected area where german armies avoided the maginot line
the Ardennes forest