Towards the close of the tenth century as the Ommeyad caliphate grew weaker, the Christian princes of Visigothic descent, who dwelt in the mountains of the Asturias, began to grow more bold in their attacks on the declining power; and in 997 Bermudo II., king of Gallicia, won back the first portion of modern Portugal from the Moors by seizing Oporto and occupying the province now known as the Entre Minho e Douro. At the beginning of the eleventh century, the great Moorish caliphate finally broke up, and independent Mohammedan emīrs established themselves in every large city, against whom the Christian princes waged incessant and successful wars. In these wars the Celtic inhabitants of the peninsula took but little part; the Moorish armies consisted of Mohammedans, the descendants of the fierce soldiers of Abder-Rahmān and a few Mosarabs, while the Christian armies consisted only of the feudal chivalry of the northern mountains. In each army different customs prevailed; the strength of the Moors lay in their perfect military discipline and absolute obedience to their generals; that of the Christians in the new impulse to valour given to each individual knight by the laws of chivalry. On neither side was personal ambition without an incentive; Moorish generals hoped to become emīrs, Christian knights, feudal counts. The finest soldiers of both armies were foreigners to the peninsula, being on the one side Africans, on the other either of Gothic descent or else the flower of the chivalry of northern Europe, which went to win its spurs in the wars against the unbelievers, and especially admired and followed the Cid, Rodrigo Diaz de Bivar. Between these two contending bands of warriors the unfortunate Celtic inhabitants of the middle zone of the peninsula were crushed; those of the mountains of the north were by feudal custom obliged to take up arms to follow their lords, and after a century or two those of the centre by the force of necessity became warriors also, and proceeded to drive the Moors back to Africa.