The Gibraltar Crusade: Castile and the Battle for the Strait, 

The epic battle for control of the Strait of Gibraltar waged by Castile, Morocco, and Granada in the late thirteenth and early fourteenth centuries is a major, but often overlooked, chapter in the history of the Christian reconquest of Spain. After the Castilian conquest of Seville in 1248 and the submission of the Muslim kingdom of Granada as a vassal state, the Moors no longer loomed as a threat and the reconquest seemed to be over. Still, in the following century, the Castilian kings, prompted by ideology and strategy, attempted to dominate the Strait. As self-proclaimed heirs of the Visigoths, they aspired not only to reconstitute the Visigothic kingdom by expelling the Muslims from Spain but also to conquer Morocco as part of the Visigothic legacy. As successive bands of Muslims over the centuries had crossed the Strait from Morocco into Spain, the kings of Castile recognized the strategic importance of securing Algeciras, Gibraltar, and Tarifa, the ports long used by the invaders.
At a time when European enthusiasm for the crusade to the Holy Land was on the wane, the Christian struggle for the Strait received the character of a crusade as papal bulls conferred the crusading indulgence as well as ancillary benefits. The Gibraltar Crusade had mixed results. Although the Castilians seized Gibraltar in 1309 and Algeciras in 1344, the Moors eventually repossessed them. Only Tarifa, captured in 1292, remained in Castilian hands. Nevertheless, the power of the Marinid dynasty of Morocco was broken at the battle of Salado in 1340, and for the remainder of the Middle Ages Spain was relieved of the threat of Moroccan invasion. While the reconquest remained dormant during the late fourteenth and early fifteenth centuries, Ferdinand and Isabella conquered Granada, the last Muslim outpost in Spain, in 1492. In subsequent years Castile fulfilled its earlier aspirations by establishing a foothold in Morocco.