In May 1940, there occurred the most mystifying event in the history of modern war. In the First World War, during four long years, the German army had tried in vain to break through the French lines. The fantasy of the historians was particularly stimulated by the notion of the so-called Blitzkrieg economy. Adolf Hitler's Blitzkrieg economy proves to be, upon closer examination, a fiction. After crossing the Meuse at Sedan, the German Panzer divisions were to turn westward toward the Channel coast. In the First World War, the general in charge, Jean Flavigny, was supposed to: seal off the enemy attack frontally via a defensive line along the massif de Stonne, and attack in the direction of Sedan as soon as possible. But this was-in the case of a tank offensive-self-contradictory, since the defensive and offensive portions of the order excluded each other.