As in former ages the progress of the Moslems was retarded and the stability of their empire endangered and finally undermined by intestine quarrels, so now, on the other hand, the jealousies and contentions of the rival kingdoms of Castile and Aragon were destined to prolong for centuries their struggle for national and religious supremacy. The intrigues of hostile chieftains, the greed and ambition of the clergy, the passions of dissolute and unprincipled women, the unnatural aversion of two nations identical in origin, proud of the same traditions, professing the same theological dogmas; the prejudices of the fanatical masses, absolutely controlled by a despotic and ignorant priesthood, were all-important factors in determining the policy of the as yet unorganized Christian states of the Peninsula. The mutual hostility of the kingdoms subsequently united under Ferdinand and Isabella insured the continuance of Moorish dominion far more effectually than the levying of contributions, the forming of alliances, the enlistment of armies. Bodies of Moslem mercenaries served alternately with the troops of both contending parties, and those who fought side by side to-day might meet as enemies to-morrow. Not infrequently impoverished and unscrupulous vassals of the Christian monarchs were induced to revolt before a projected invasion by the judicious employment of Moorish gold. Thus arrayed against each other, with treachery in their camps and foes in their rear, the Spanish princes were constantly hampered in the execution of their plans of conquest. Other causes contributed to their want of success. The Christian generals could often win, but were seldom disposed to improve a victory. Feudal independence, now first interposed as a disturbing force, was implacably hostile to discipline; the vassal obeyed his suzerain; but the noble whose origin was often as illustrious as that of his king was only too ready to question, or even to defy, the regal authority. The incapacity to appreciate the resultant advantages of military success was also a characteristic of the Moors. A great battle usually ended a campaign. But the enemy was rarely pursued beyond the field; his camp was overrun by a disorganized mob in search of plunder; his baggage was ransacked; his seraglio appropriated; his wounded massacred. The dispersed remnants of his army were afforded abundant time to reorganize and to again become formidable. The ability of the Moslems to profit by the discomfiture of an adversary disappeared with the great soldier Al-Mansur. Generations were to elapse before the Spanish commanders, recognizing untiring energy as an indispensable requisite of permanent success, were enabled to plant their banners on the towers of Cordova and Seville. In no great contest described in history were such fierce battles fought, such bodies of men dispersed, such losses of life sustained, and such paltry results accomplished.