His attention, however, was directed elsewhere. His legal work *Las siete partidas* was inspired by Roman law, and his political activity revealed an absolutist tendency against which the nobles of the kingdom took up arms. Reviving old ambitions of his ancestors, he aspired to make Spain the center of European politics by securing the imperial crown: in 1257 some German Electors elected him King of the Romans, but he never dared to address the issue of a journey to Germany. Although he established the principle of succession by the eldest son and his descendants, the death of his son and heir Ferdinand de la Cerda forced him, under pressure from the nobility, to recognize his second son Sancho as heir instead of his grandsons the de La Cerdas; later he changed his mind and acknowledged the legitimate rights of his grandsons. The reign of Sancho IV was marred by the struggle against the de La Cerdas. The conflict worsened due to the intervention of the King of France on behalf of the de La Cerdas, and only in 1308 was the matter settled with compensation paid to the claimants. At the beginning of the 14th century there was military activity against Granada; once peace was restored, the Moorish King of Granada agreed to pay tribute. The early death of Ferdinand IV (1295–1312) was followed by the long reign of Alfonso XI (1312–1350), which was plagued by prolonged civil strife over the claims of various princes to the regency and later to the government. More violent struggles erupted after 1350 between Peter the Cruel, son of Alfonso XI by his first marriage, and his illegitimate half-brother Henry of Trastámara, who had himself proclaimed king in 1366. France and England intervened in the conflict, and the war in Castile became a lively episode of the Hundred Years' War. With French support, Henry of Trastámara prevailed and succeeded in ending the conflicts with neighboring monarchies; his heir John I reconciled with England by arranging the marriage of his son Henry—who was the first to be called Prince of Asturias—to an English princess. Henry III ascended the throne amid a new phase of struggles among the princes for the regency; once peace was restored, he began a notable military campaign, destroying the pirates of Tetuan and occupying the Canary Islands. During this period, the internal political life of the Kingdom of Aragon proceeded more quietly, as it was preoccupied with Mediterranean issues.
Peter III, son and successor of James I, having married Constance, daughter of Manfred, the Swabian King of Sicily, landed at Trapani in August 1282 to aid the Sicilians who had rebelled in March against King Charles of Anjou. The war between Anjou and Aragon was complicated by the intervention of the Pope and the French monarchy. Boniface VIII, in 1295, granted James II the islands of Sardinia and Corsica under the Treaty of Anagni, but Frederick, James’s brother, retained Sicily under the Treaty of Caltabellotta. The conquest of Sardinia occupied the reigns of Alfonso IV (1327–1360) and Peter IV the Ceremonious (1336–1370): the Aragonese kings, forced to fight against the Republics of Genoa and Pisa, which had interests in the two great islands, sought an alliance with Venice. Under John I (1387–1395) the question of Sicily resurfaced with the extinction of that branch of the Aragonese dynasty: Martin, who had married Maria, heiress to the Sicilian kingdom, died in 1409, leaving the island to his father Martin I, who had succeeded his brother John in Aragon.
5. The internal organization of the Spanish states in the 14th–15th centuries
Formed slowly through successive conquests over various centuries, the Spanish states bore all the characteristics of a conglomeration of different regions with distinct institutions and customs. The kings who had led their warriors to war against the infidels had gained privileges and wealth. They granted lands to those who aided them in the conquest, but feudalism of the Frankish type did not take root in Spain, with the exception of Catalonia, a Carolingian march.Beside the kings stood the *ricos hombres*, who in the 13th century formed the major councils to ensure the indivisibility of the family patrimony; below them were the *hidalgos*, an ancient nobility, and the *caballeros*, a noble class open to those who could provide themselves with a horse and arms. In Aragon, Catalan feudalism gradually took hold. The cities enjoyed a special status due to the liberties or privileges obtained through conquest and recorded in their *fueros*.