The number of the Mozárabes of course diminished rapidly in the progress of reconquest as the Christian territories expanded from Galicia to Leon and Castile. Early in the twelfth century Alfonso VI, in reducing to order his extensive acquisitions, experienced much trouble with them; they are described as being worse than Moors, and he settled the matter by the decisive expedient of deporting multitudes of them to Africa.[137] The rapid progress of his arms, however, had so alarmed the petty kings among whom Andalusia was divided that they had, about 1090, invited to their assistance the Berbers known as Almoravides, who drove back Alfonso on the bloody field of Zalaca. Their leader, Jusuf ibn Techufin, was not content to fight for the benefit of his allies; he speedily overthrew their feeble dynasties and established himself as supreme in Moslem Spain. The Almoravides were savage and fanatical; they could not endure the sight of Christians enjoying freedom of worship, and bitter persecution speedily followed, until, in 1125, the Mozárabes invited the aid of Alfonso el Batallador. They sent a roll of their best warriors, comprising twelve thousand names, and promised that these and many more would join him. He came and spent fifteen months on Moorish territory, but made no permanent conquests, and on his departure the wretched Christians begged him to let them accompany him to escape the wrath of the Almoravides. Ten thousand of them did so, while of those who remained large numbers were deported to Africa, where they mostly perished.[138] The miserable remnant had a breathing spell, for the atmosphere of Spain seemed unpropitious to fanaticism and the ferocity of the Berbers speedily softened. We soon find them fraternizing with Christians. King Ali of Córdova treated the latter well and even entrusted to a captive noble of Barcelona named Reverter the command of his armies. His son Techufin followed his example and was regarded as the especial friend of the Christians, who aided him in his African wars.[139] Yet this interval of rest was short. In 1146, another Berber horde, known as Almohades, overthrew the Almoravides and brought a fresh accession of savage ferocity from the African deserts. Their caliph, Abd-al-mumin, proclaimed that he would suffer none but true believers in his dominions; the alternatives offered were death, conversion or expatriation. Many underwent pretended conversion, others went into voluntary exile, and others were deported to Africa, after which the Mozárabes disappear from view.[140]