9.7 Military adventures
Perhaps the most obvious of these changes was the much greater military efficacy of northwestern European society from the eleventh century onward, as feeble defense gave way to formidable aggression. This was most evident on the frontiers of Christendom. Knights from the northwest played roles of varying prominence in the reconquest of Spain and Sicily from the Muslims, the establishment of Crusader states in the eastern Mediterranean, and the conquest of pagan territory in the northeast. But the military edge of the old northern cradle of the Frankish state was also manifested within the boundaries of the Christian world by conquests in England, Ireland, and the south of France. The military basis of these developments was a particular use of an invention of the early Middle Ages that reached Europe from the east-the stirrup. The Franks and those who fought like them used it to perfect a style of warfare in which the ultimate weapon was the disciplined charge of heavily armored cavalry. As a Byzantine princess remarked of the Franks, "a mounted knight is irresistible; he would bore his way through the walls of Babylon." An army of this kind went well with the domination of peasant society by a warrior aristocracy.