[Illustration: Fig. 40.--Dagger with Moorish Blade and Flemish Handle (Fourteenth Century).--Collection of M. Onghena, Ghent.] In all probability the establishment of the _arrière-ban_, or the _ban-fieffe_, dates from the sixth century. It was a call to arms of the vassals that the suzerain alone had a right to command. A century later, feudalism, which was beginning to establish itself in Gaul as in Italy, as a consequence of the successful invasion of the Franks, was nearly stamped out by the Mahometan invasion of the Spanish Moors, who had been led by their chief, Abderamus, as far as the banks of the Loire, where they were stopped by Charles Martel, who routed them with great slaughter. After the brilliant victory of Poitiers (732), where the repulse of Arab civilisation left the field open to the defenders of the Christian faith, and to the originators of the feudal régime, the victorious army underwent a sudden change. The Frankish knights adopted as an inheritance of conquest the rich Saracen armour (Figs. 37, 38, 39, 40); the feudal troopers donned a coat of mail, and, henceforward, a full suit of armour became a necessary accessory to a warrior of high rank. The bow, which had long been thrown aside, was once more taken into favour, and became the special arm of the footmen. But we have exhaustively treated of the armament and equipment of the soldiery of the period (see the chapter on Armoury in “Art in the Middle Ages”), and we can only here deal with military tactics and organization; in a word, with the theoretical part of the art of war.