The naval prominence of Castile in the late medieval and early modern period has been amply researched. However, the rise of the Castilian navies and their fundamental role in the thirteenth and fourteenth-century Castilian expansion have not been addressed properly. One of the principal reasons has been the relatively small amount of coverage of naval affairs in the chronicles, and the dearth of documentation in the archives in comparison to ground warfare and forces. After all, the Castilian elite, which takes up most of the attention in the sources, did not routinely train in maritime or naval matters as part of its upbringing. Maritime and naval historians, perhaps, have somewhat exacerbated the situation by appearing to treat naval issues separately from those of fighting on land.

Such a demarcation is untenable in Castile. The growth of its navies coincided with, and was important, if not fundamental, in its expansion and consolidation, which was accompanied by an increasing awareness and embrace of the importance of seafaring and the conquest and defense of the coasts. Castile struggled against not only the Muslims in the Iberian Peninsula and North Africa, but also the kingdoms of Aragon and Portugal and the Italian city-states, especially Genoa, which sought to establish and protect commercial interests in the Mediterranean and the Maghreb. Since all of these conflicts invariably included a naval component, more analysis is necessary to fully understand how, when, and why the Reconquest unfolded as it did. Just as the Muslim territorial domination gave way to Christian southern expansion, so too the coastlines and sea lanes, in the Atlantic, the Strait of Gibraltar, and the Mediterranean, were gradually wrested away from total Islamic domination during the thirteenth and fourteenth centuries. This was accomplished by following a familiar strategy of the capture and defense of important strongpoints, and only through difficult and slow progress. As Castile and Aragon emerged as the two top naval powers, their uneasy balance and later union in the fifteenth century signaled the end of any serious Muslim naval aspirations or capability, whether in Granada or North Africa. Navies played only a small role in the final defeat and annexation of Granada by the Catholic kings in 1492.