On the occasion of Charles’s own marriage, the dowry from the wealthy royal family of Portugal had provided him at a critical juncture with money to carry on the war with France; and now again, with his exchequer chronically empty, and the demands upon it for warlike purposes more pressing than ever, the emperor sought to tap the rich stream of the Portuguese Indies by wedding his son to Princess Maria, daughter of John III. and of Charles’s sister Catharine, another consanguineous marriage of which we shall see the result later. Before the affair could be concluded the emperor was obliged to leave Spain (May 1543). In July of the previous year Francis I. had fulminated against his old enemy his famous proclamation of war, and to Charles’s troubles with the Protestants of Germany was now added the renewed struggle with France, in which he was to have the assistance of the English king. The emperor’s intercourse with his son during his stay in Spain had convinced him of Philip’s precocity in statesmanship, and so he determined to leave in his hands the regency of Spain in his absence.
This was one of the most important junctures of Philip’s life. He was barely sixteen years old, and was thus early to be entrusted with Charles’s secret system of government, an instruction which left deep marks upon Philip’s own method for the rest of his life. The two letters written by Charles to his son before his departure from Spain are of the utmost importance as providing a key for Philip’s subsequent political action. Although Philip was entrusted with the ultimate decision of all subjects, he was to be guided by some of the most experienced and wisest of Charles’s councillors. First there was the Cardinal-Archbishop of Toledo, Tavara, and next the Secretary of State, Francisco de los Cobos, who had been at the emperor’s right hand for so long. The young regent is secretly told by his father that the reason why these two were appointed as his principal councillors was because they were respectively heads of factions, and their rivalry would prevent the prince from falling under the influence of either political party. With merciless scalpel the great emperor lays bare, for the benefit of the lad of sixteen, the faults and failings of the statesmen who are to aid him in the government. He is warned not to trust any of them separately. Their hypocrisy, their greed, their frailties of character, and conduct are pointed out by the worldly-wise ruler to the neophyte; and the moral of it all is that he should listen to the opinions of every one, and especially of rivals, and then decide for himself.