In the Wars of Granada (1480-92) he began to practice his tactical innovations, which surpassed medieval warfare of clashes between cavalry lines with the greater maneuverability of mercenary infantry in solid units; His ability to take advantage of all resources, adapting tactics to the conditions of the moment (using, for example, spies to gain the advantage of information, or practising guerrilla warfare in some of his campaigns), explains the successes of his career, which made him the most prominent military commander of the Castilian-Aragonese monarchy from a young age.

The kings entrusted him with several embassies to negotiate with King Boabdil the Younger of Granada, with whom he had friendly relations. The services he rendered during that campaign were rewarded with an encomienda of the Order of Santiago, in addition to other rents and lordships.

With the Reconquista completed with the capitulation of Granada (1492), Isabella and Ferdinand employed him in Italy, where they would wage a long war contesting hegemony in the region against France. The French invasion of Naples – claiming the inheritance of the House of Anjou – was answered with a two-year campaign (1494-96) led by Fernández de Córdoba, who defeated the French and restored the Neapolitan monarch, who belonged to the Aragonese royal family. The successes of that war (such as the capture of Reggio, Atella and Naples) earned him the nickname of Grand Captain and the title of Duke of Santángelo.

He returned to Spain in 1498, but soon had to return to Italy when France and Aragon settled their dispute with the Treaty of Granada (1500), which divided the kingdom of Naples into two areas: the north for France and the south for Aragon. Fernández de Córdoba himself was placed in command of the army that occupied Naples, wresting the throne from the dynasty he had defended four years earlier.

French expansionism also provoked the reopening of the conflict with Spain in 1502. It defeated them in the open at the battles of Ceriñola, Garellano and Gaeta (1503). Naples thus came under Spanish rule, under which it remained until the 18th century, with Gonzalo remaining governor of the kingdom.

The death of Queen Isabella the Catholic in 1504 marked the beginning of the Gran Capitan’s fall from grace. His confrontation with Ferdinand the Catholic reached a climax following the Treaty of Blois (1505), by which the king returned to the French Crown the Neapolitan lands that Fernandez de Cordoba had expropriated from the princes of the House of Anjou and distributed among his officers. In 1507 Ferdinand travelled to Naples to take possession of his new kingdom, at which time legend has it that he demanded that the Great Captain account for his financial management; in any case, he was deposed as governor of Naples, where he never returned despite his protests.

The king’s unjustified misgivings increased and, as he had to return to Spain to take charge of the situation due to the recent and unexpected death of his son-in-law Philip I, he ordered the Grand Captain to hand over his command and return with him to Spain. The year was 1507. Once there he kept him away from any office. On one occasion he had sworn to him by “God our Lord, by the Cross and the four Holy Gospels that he would resign in his favour” the office of Master of Santiago, but he failed to fulfil this sacred oath and denied the Grand Captain what he had promised, so that the latter retired to Loja, a city that the Monarch granted him, tired and disillusioned. In 1512 he broke his friendship with King Ferdinand the Catholic. He died in the city of Loja in 1515.