Fernando III. was succeeded by his son Alfonzo X., _El Sabio_, 'the Learned.' He occupied the Palace of the Alcázar, and devoted his leisure to the study of geometry, ancient laws, history and poetry. The King wrote verse to the Virgin in the Galician dialect, which resembles the Portuguese tongue, and was, for his age, a versatile and accomplished scholar. His ambition was great, and though he was called 'the Learned,' he was prone to serious error in the conduct of the affairs of government. He attempted to take Gascony, which was then in the possession of Henry III. of England, and governed by Simon de Montfort. The King's military enterprises were costly, and as they failed, the people resented the increase of taxes, and especially the measure of direct taxation. When Alfonso presented Algarve to the King of Portugal, with his natural daughter, Beatrice de Guzman, the nobles rebelled under the King's brother, Felipe, and were aided by the King of Granada. Alfonso invited the malcontent party to a conference of arbitration at Burgos. The knights were appeased; but the King was forced to yield his ground, and to make many concessions. Upon the death of Alfonso's eldest son, Fernando, a dispute arose concerning the heir to the crown. Fernando left two sons, born to him by Blanche, sister of Philip IV. of France. The second son of Alfonso, Sancho, was announced as rightful successor, but this proclamation was a cause of offence to Philip IV., who claimed that the eldest child of his sister was the lawful heir to the throne of Castile. The King of France demanded that Alfonso should restore the dowry to Blanche, and allow her and the children to come to France. Alfonso refused the request. War was then declared by Philip of France; and further anxiety was caused by the disloyalty of Sancho, who took the lead of the discontented party, and laid siege to Toledo, Córdova, and other towns. The King was at his wit's end. He begged aid from Morocco, from the infidels, while, at the same time, he desired the Pope to excommunicate Sancho. Eventually the quarrel between King and Prince was patched up. Alfonso appears to have cherished affection for his unruly son, for upon hearing, soon after the reconciliation, that Sancho was seriously ill, the King died of grief.