The germans have diverted the French-German border 2 times.
In WW1 there was the "plan-schlieffen" which ment the invasion of belgium then into northern france. In that plan the heavy artillery pieces like this one were crucial in order to destory the belgium fortresses at namur and liege, because infantry rush at a fortress is useless.
The plan Schlieffen and the rest of the western front 1914-1918 can be viewed up here:
TGTW history section
Also i never said bertha was the biggest
