For the Christians of the north were now on the move. They saw their opportunity, and they made the most of it. Alfonso VI., who had united under his sway the three kingdoms of the Asturias, Leon, and Castile, understood his part perfectly. He saw that he only had to allow the various Moslem princes rope enough, and they would proceed to hang themselves with the utmost expedition. These short-sighted tyrants, indeed, caring only for their petty individual power, and eagerly aiding in anything that could weaken their rivals, threw themselves at Alfonso's feet, and implored his assistance whenever they found themselves overmastered by a more powerful neighbour. Partly in consequence of acts of this kind, and partly in terror at the furious raids which the Castilians made throughout the country, even as far as the port of Cadiz, the Moslem States were almost all tributaries of the King of Castile, who took care to annually demand heavier and more heavy tribute, as the price of his friendship, in order to lay up stores for the great conquest which he had in mind. The north was poor, and with a fine irony he trusted to the immense contributions of his vassals among the Andalusian princes to provide the sinews of the war which should destroy them. Divided and jealous as were the Mohammedan dynasts, there was a limit to their patience. When Alfonso had bathed in the ocean by Hercules' Pillars, rejoicing that at last he had traversed all Spain and touched the watery border; when he had established a garrison of more than twelve thousand daring men in the fortress of Aledo, in the very midst of the Moslem territories, whence they ruthlessly emerged to harry the whole country and commit every sort of savage outrage; when Rodrigo Diaz de Bivar, "my Cid the Challenger," had established himself in Valencia with his Castilians, and laid waste the neighbouring lands; when it became clear to everyone that Alfonso meant nothing less than the reconquest of all Spain, and the extermination of all Moslems--then at last the Mohammedan princes awoke to their danger, and began to take measures for their defence. Helpless in themselves and, in spite of the common danger, despairing of any firm collected action among so many and such hostile factions, they took the only other course possible--they called in the aid of the foreigner. Some, indeed, foresaw dangers in such aid; but Mo'temid, the King of Seville, silenced them: "Better be a camel-driver in African deserts," he said, "than a swineherd in Castile!" The power they required was not far off. A new Berber revolution had taken place in North Africa, and a sect of fanatics, called the marabouts or saints (_Almoravides_, as the Spaniards named them), had conquered the whole country from Algiers to Senegal. They were much the same sort of people as Tārik and his followers, and they were ready enough to cross the water and conquer the fertile provinces of Spain. They made it a favour, indeed, and evinced supreme