Castile is the principal domestic arena in which Ferdinand of Aragon built the reputation and authority that made him, in the book’s judgment, almost a new Prince. Its significance lies less in a description of its geography than in its political use: Ferdinand occupied the Barons of Castile with the war against Granada, drew money from the Church and his subjects to sustain that campaign, and converted a prolonged external conflict into a foundation for internal control and wider expansion.

Castile as the Foundation of Ferdinand’s Power

At the beginning of Ferdinand’s reign, Castile is described as politically weak, while Ferdinand himself was still far from being the dominant king he would become. His war against Granada supplied the decisive enterprise through which that condition changed. He conducted the campaign at first deliberately and without fear of interruption, keeping the Barons of Castile so fully absorbed in the war that they had no leisure to contemplate domestic changes. Military action therefore served two purposes at once: it advanced Ferdinand’s territorial aims and prevented the kingdom’s leading men from turning their attention toward opposition at home.

The campaign also allowed Ferdinand to acquire authority gradually rather than merely claim it. As the war continued, he accumulated reputation among the Barons and increased his power over them. The conflict became a political school in which obedience was practiced under the pressure of a common enterprise. Castile’s internal hierarchy was not abolished; instead, its potentially troublesome elites were kept occupied, while Ferdinand’s command acquired legitimacy through repeated action and visible results.

Finance, Religion, and Military Organization

The war in Granada was maintained with money drawn from the Church and from Ferdinand’s subjects. This financial arrangement made the campaign an instrument of state-building: resources gathered from established religious and social institutions supported armies that in turn strengthened the Crown’s authority. The prolonged nature of the war was important because it gave Ferdinand time to establish the military discipline for which he later became famous. Castile thus supplied not only soldiers and revenue but also the duration necessary for military habits to become a durable political foundation.

Ferdinand further enlarged the meaning of the campaign by presenting his undertakings under the cloak of religion. The text associates this policy with the expulsion of the Moors from his Kingdom, an act characterized as pious cruelty and described as extraordinarily impressive. Within Castile, religious justification made coercive consolidation appear as a sacred enterprise. The same religious pretext then accompanied Ferdinand’s war in Africa, his invasion of Italy, and his eventual attack on France, turning the kingdom’s initial campaign into the opening movement of a sequence of increasingly ambitious designs.

The Barons and the Management of Opposition

Castile’s Barons are central to the political mechanism described. Ferdinand did not allow them the unoccupied political space in which dissatisfaction could become conspiracy or a demand for change. By making the war against Granada their dominant concern, he redirected aristocratic energy outward and tied the leading figures of the kingdom to the success of the Crown’s enterprise. Their attention was not simply distracted; it was organized around a cause whose continuation reinforced Ferdinand’s authority.

This strategy illustrates the book’s broader distinction between a Prince who merely possesses power and one who continually creates the conditions of obedience. Ferdinand’s authority in Castile grew as the campaign produced reputation, revenue, discipline, and new opportunities for action. Each result supported the next. The war generated military strength; military strength enabled further enterprises; further enterprises kept the subjects’ minds suspended between expectation and admiration, leaving little time or opportunity for organized resistance.

Castile within Ferdinand’s Expanding Policy

The conquest of Granada is treated as the foundation of Ferdinand’s power, but Castile also appears as the launching ground for a much wider program. After the initial campaign, Ferdinand used the same religious cover for war on Africa, invasion of Italy, and attack on France. These ventures were not presented as isolated episodes. They followed one another in such close succession that the consequences of one became the occasion for the next, and the constant movement of policy prevented opposition from settling into a stable force.

In this sense, Castile’s importance is both domestic and strategic. It was the kingdom in which Ferdinand first gained authority over the Barons, secured the resources for sustained warfare, and developed the military discipline required for later enterprises. Its political consolidation enabled an outward policy whose scale kept subjects occupied with the results of royal action. Ferdinand’s transformation from one of the weakest rulers into the foremost King in Christendom therefore begins in Castile, where war was made to perform the work of government.

Comparative Political Significance

The book’s account of Castile belongs to a larger analysis of how rulers acquire and preserve States. It contrasts Ferdinand’s successful consolidation with cases in which rulers depended on inherited weakness, foreign assistance, or Fortune without building adequate foundations. Francesco Sforza rose from privacy to become Duke of Milan through ability and suitable measures, while Cesare Borgia received his Princedom through the favorable fortunes of his father and lost it when those fortunes failed, despite his efforts to establish durable power. Ferdinand’s example similarly emphasizes the importance of converting opportunity into institutions, reputation, and military capacity.

The comparison also clarifies why Castile matters as a political setting rather than merely a territorial name. A ruler’s strength is measured by whether he can stand alone with the men and money at his disposal, and Ferdinand’s prolonged war helped create precisely that capacity. The kingdom’s revenues, aristocratic structure, religious institutions, and military resources were drawn into a single policy whose visible achievements increased the Crown’s authority. Castile is consequently remembered as the place where Ferdinand’s power was founded and disciplined before it was projected across Africa, Italy, and France.