The little band of refugees was strengthened from time to time by fresh accessions, and, by degrees waxing more confident, came forth from their stronghold, and began to harass the Berbers who formed the frontier settlers. The Moors were at length compelled to seek out the intrepid raiders in their cavern; but the result was discouraging; they were driven back pell-mell with great loss. In 751 Alfonso of Cantabria (where the Moslems had never penetrated), having married the daughter of Pelayo and thus united the Christian forces, roused the northern provinces against the Moors, and, joined by the Galicians of the west, began a series of brilliant campaigns, by which the enemy was driven step by step further south. One after the other the cities of Braga, Porto, Astorga, Leon, Zamora, Ledesma, Salamanca, Saldaña, Segovia, Avila, Osma, Miranda, were recovered from the Moslems, and the Christian frontier was now pushed as far as the great Sierra, and Coimbra, Coria, Talavera, Toledo, Guadalaxara, Tudela, and Pamplona became the Moslem border fortresses. Alfonso had in fact recovered the provinces of Old Castile, Leon, Asturias, and Galicia; but the scanty band of Christians had neither money nor serfs wherewith to build fortifications and cultivate the fields over so immense an area: they contented themselves with leaving the conquered country as a debatable land between them and the Moors, and retired to the districts bordering the Bay of Biscay until such time as their numbers should justify the occupation of a wider area. In the ninth century they were in a position to advance upon the territory they had already in part recovered from the Moors. They spread over Leon, and built the fortresses of Zamora, San Estevan de Gormaz, Osma, and Simancas, to overawe the enemy. The debatable land was now much narrower, and the hostile forces were almost in contact at various places along the frontier. At the beginning of the tenth century the Moors of the borders made a strenuous effort to regain their lost dominions; but the Christians, aided by the men of Toledo, and by Sancho, King of Navarre, who had become the bulwark of Christianity in the north, defeated them severely, and began to harry the country over the border. The forays of the Christians were a terrible curse to their victims; they were rude, unlettered people, and few of them could even read; their manners were on a par with their education; and their fanaticism and cruelty were what might be expected from such uncouth barbarians. Seldom did the soldiery of Leon give quarter to a defenceless foe, and we may look in vain for the fine chivalry and toleration of the Arabs; where the latter spared nobly, the rough robbers of Leon and Castile massacred whole garrisons, cities full of inhabitants, and those whom they did not slaughter they made slaves.