Up to this time Spain had been of little importance in the general affairs of Europe. The energies of its people had been entirely spent in fighting one long crusade against their Moorish conquerors. The disunion between the small Christian kingdoms long hindered their success against the Moors. But in 1230 the Christian kingdoms of Castile and Leon were united under one ruler, who, being wise and powerful, succeeded in winning back a large territory from the Moslem. The Kings of Portugal and Aragon had also been successful in the west and east of the peninsula, and at last nothing was left of the Mahometan power in Spain save the kingdom of Grenada. It is easy to understand, that whilst the kingdoms of Spain were disunited, and were engaged in this desperate struggle against the Moors, on which their very existence as a nation depended, they had no time to interfere in the affairs of Europe, and except for the connexion of the Kings of Aragon with Naples and Sicily, remained almost entirely outside European politics. Now, however, things were more settled in Spain. It was divided into five kingdoms, the four Christian kingdoms of Castile, Aragon, Portugal, and Navarre, and the Mahometan kingdom of Grenada. Of these Castile was the largest, and had, from its neighbourhood to the Duchy of Aquitaine, been connected with the Kings of England. A daughter of Henry II. of England had been married to the King of Castile, and Edward I. had married Eleanor of Castile, who had known well how to gain the love and veneration of the English people. As Dukes of Aquitaine, it was the policy of the English Kings to be on friendly terms with the Kings of Castile. Contending commercial interests had provoked discord from time to time, as we have seen in speaking of the great sea fight of Winchelsea, when Edward III. defeated the fleet of the maritime cities of Biscay; but this was in no way a quarrel between the two monarchs, and their friendly relations remained unchanged. So it happened that when the King of Castile, Don Pedro, was chased from his throne on account of his cruelty and tyranny, he turned naturally to the Black Prince, hoping to find in him a friend. He had been engaged to marry the Prince's sister, the Princess Joan, who had died of the plague at Bordeaux on her way to Spain. He called himself therefore the Prince's brother-in-law, and considered that he had a claim to the Prince's friendship.