The engineers of the Empire developed in Alsace and in Lorraine all the techniques coming from the art of fortifying in Germany: from Alexis von Biehler's forts in Strasbourg to the strongholds on the square of Metz. During 45 years, Germany built on its frontiers with France a coherent defensive system, consistent with its strategy and adapted to the army's operational plans proposed by Von Schlieffen: "the Empire's occidental shield."

This fortified system has not been fully tested during the Great War, which has helped to create this idea of an undefeated, mighty and modern system.