From Imperial Spain: 1469-1716, by J. H. Elliott (Penguin, 2002), 2nd ed., Kindle Loc. 3427-3580:
From the moment of his Imperial election Charles V found himself saddled with enormous commitments. The struggle with France in the 1520s, the offensive and defensive operations against the Turks in the 1530s, and then, in the 1540s and 1550s, the hopeless task of quelling heresy and revolt in Germany, imposed a constant strain on the Imperial finances. Always desperately short of funds, Charles would turn from one of his dominions to another in the search for more money, and would negotiate on unfavourable terms with his German and Genoese bankers for loans to carry him over the moments of acute penury, at the expense of mortgaging more and more of his present and future sources of revenue. This hand-to-mouth existence had prompted, in the very first years of the reign, gloomy prophecies about the certainty of financial shipwreck, but, in fact, it was not until 1557, when Philip II had succeeded his father, that the expected bankruptcy materialized. Until then, Charles’s appeals to the generosity of his subjects and his constant recourse to loans from the bankers somehow managed to stave off the moment of disaster; but the price paid was a renunciation of any attempt to organize the Imperial finances on a rational basis and to plan a coherent economic programme for the various territories of the Empire.
The main cost of financing Charles’s imperialism was borne by different territories at different times, depending on their presumed fiscal capacity and on the facility with which money could be extracted from them. The territories concerned were primarily European, for the part played by the new American possessions in financing Habsburg policies during the first half of the sixteenth century was relatively very small. Until the 1550s the Crown’s revenues from America averaged only some 200,000–300,000 ducats a year, as compared with the 2,000,000 ducats a year of the later years of the reign of Philip II. This meant that the real entry of the New World into the Habsburg empire was delayed until the decade 1550–60, and that Charles V’s imperialism, unlike that of his son, was essentially a European-based imperialism. Among the European territories of Charles it was the Netherlands and Italy which bore the brunt of the Imperial expenditure during the first half of the reign. But as each in turn began to be squeezed dry Charles was compelled to look elsewhere for further sources of revenue, and by 1540 he was writing to his brother Ferdinand: ‘I cannot be sustained except by my kingdoms of Spain.’ Henceforth, the financial contributions of Spain – which meant essentially Castile – assumed a constantly increasing importance in relation to those of the Low Countries.
Within Spain there were several potential sources of revenue, both secular and ecclesiastical. The financial contribution of the Spanish Church to Habsburg imperialism in the sixteenth and seventeenth centuries still awaits an adequate study, but its importance would be difficult to overestimate. If the Lutheran princes of Europe were to gain great benefits from breaking with Rome and despoiling the Churches in their territories, the kings of Spain were to show that despoiling the Church was equally possible without going to the lengths of rupture with the Papacy, and that the long-term advantages of this method were at least as great, and probably greater. It was difficult for the Papacy to refuse new financial concessions when the, Faith was everywhere being endangered by the spread of heresy; and the Spanish Crown, by placing no restrictions on mortmain, could further the accumulation of property in the hands of the Church, where it was more readily available for taxation.
Charles V’s fantastically expensive foreign policies and his dependence on credit to finance them therefore had disastrous consequences for Castile. The country’s resources were mortgaged for an indefinite number of years ahead in order to meet the Emperor’s expenses, a large proportion of which had been incurred outside Spain. His reliance on credit contributed sharply to the prevailing inflationary trends. Above all, the lack of provision in the Crown’s financial policies – its inability to devise any coherent financial programme – meant that such resources as did exist were squandered, while the methods used to extract them might almost have been deliberately designed to stunt the economic growth of Castile. The reign of Charles V, in fact, saw three dangerous developments that were to be of incalculable importance for sixteenth- and seventeenth-century Spain. In the first place, it established the dominance of foreign bankers over the country’s sources of wealth. Secondly, it determined that Castile would bear the main weight of the fiscal burden within Spain. In the third place, it ensured that within Castile the brunt of the burden was borne by those classes which were least capable of bearing it.