William the Red's arms were as successful against Wales as against Scotland. During his reign the southern half of the land of the Cymry was overrun by Norman barons, who won for themselves new lordships beyond the Wye and Severn, and did homage for them to the king. Many of these adventurers married into the families of the South Welsh princes, and became the inheritors of their local power. In North Wales the Normans pushed across the Dee, and built great castles at Rhuddlan and Flint and Montgomery, but they could not win the mountainous districts about Snowdon, where the native chiefs still maintained a precarious independence. [Sidenote: =William obtains possession of Normandy.=] Beyond the British seas William waged constant war with his brother Robert, and always had the better of his elder, for the duke, though a brave soldier, was a very incapable ruler, and lost by his shiftless negligence all that he gained by his sword. He was forced in 1091 to cede several of his towns to William, and to promise to make him his heir if he should die without male issue. But in 1096 the king gained possession of the whole, and not a mere fraction, of the Norman duchy. For Robert, seized with a sudden access of piety and a spirit of wandering and unrest, vowed to go off to the First Crusade, which was then being preached. In order to get the money to fit out a large army, he unwisely mortgaged the whole of his lands to his grasping brother for the very moderate sum of £6666. So William ruled Normandy for a space, and Robert went off with half the baronage of Western Christendom, to deliver the Holy Sepulchre from the Turks, and to set up a Christian kingdom in Palestine. Among his companions were the Etheling Eadgar, and many Englishmen more. The duke fought so gallantly against the infidel that the Crusaders offered him the crown of Jerusalem; but he would have none of it, and set his face homeward after four years of absence (1099). [Sidenote: =William's extortions.--Quarrel with the Church.--Anselm.=]