From wasting the power of his kingdom in African wars Affonso V. turned to a still more fatal pursuit, the encouragement of his dream of sitting on the throne of Castile. The lessons of his grandfather’s reign were lost on him; he failed to understand that the two countries had developed on separate lines and could not coalesce, and did not see that in a contest Portugal, owing to her smaller population, must needs have the worst of it, unless the war were national and calculated to rouse the spirit of enthusiasm and not merely dynastic. His family was now at the height of its fame--his aunt Isabel was Duchess of Burgundy; his eldest sister had married the Emperor Frederick III.; his youngest sister had married Henry IV. of Castile; and his remaining sister, Catherine, had been sought in marriage by the son of the King of Aragon and by Edward IV. of England. His first wife, Isabel, the daughter of the great regent, Dom Pedro, had died in 1455, after giving birth to the prince who was to be John II., and it was not until after his third expedition to Africa that he contemplated a fresh marriage, which should give him a claim to the succession to the throne of Castile. With this idea Affonso V. married his own niece, Joanna, elder daughter of Henry IV. of Castile (though but a girl of thirteen), in 1475, and he claimed the kingdom of Castile in her name. But the Castilians preferred the Infanta Isabella, who had married Ferdinand, King of Aragon, and they were as determined to prevent a Portuguese king from sitting upon their throne, as the century before the Portuguese had been against the union of their country with Castile. The Castilians, fighting for their independence, as utterly defeated the Portuguese at Toro in 1476 as the Portuguese had defeated them at Aljubarrota in 1385. Affonso hurried to France, to beg help from Louis XI.; but his supplication was unheeded, and in 1478 he found himself constrained to sign the Treaty of Alcantara, by which he agreed to send his newly-married bride to a convent. He remained inconsolable at this failure of his schemes, and alternately abdicated and returned to the throne, until his death in 1481.