King of Castile (1312-1350).
The son of King Ferdinand IV of Castile and Constance of Portugal, Alfonso came to the throne as a minor. During his adolescence, the political turbulence of the preceding reign continued. In 1325 he came of age, and from then on was extremely active in his attempts to restore the authority of the monarchy and to neutralize the threat from the Marinid dynasty of North Africa. In respect of the former aim, he was a worthy continuator of the centralizing politics of his greatgrandfather Alfonso X: by promulgating the Ordenamiento de Alcalà in 1348, he established Roman-canonical law in the kingdom. Against the Marinid sultan, who had been sending troops to the Iberian Peninsula since 1338, Alfonso concluded an alliance with the kingdom of Aragon and also with Genoa, which put ships at his disposition to block the Strait of Gibraltar; there was a further alliance with Portugal, which participated actively in the battle of the river Salado, near Tarifa(1340). In this campaign, declared a crusade by Pope Benedict XII, the allied troops, helped by an impressive participation of the military orders, defeated the Marinids and their Granadan allies. This victory meant the end of the African invasions of the Peninsula, although the Marinids retained a presence in Algeciras and Gibraltar. In 1343 Alfonso conquered Algeciras, taking advantage of the new artillery technology, but died seven years later while besieging Gibraltar. He was succeeded by his son Peter I “the Cruel.”