December 15, 1471, Sixtus made Pietro Riario, his putative nephew, but probably his son, Cardinal of San Sisto, and Giuliano della Rovere, son of his brother Raffaele, Cardinal of San Pietro ad Vincola, thus breaking his oath. Both these young men were of low origin and no education, and the Sacred College little suspected that one of them, Giuliano, was destined to become the famous Julius II.
Giuliano della Rovere, who was Bishop of Carpentras, was twenty-eight years old, a libertine and man of the world. Pietro Riario was somewhat younger and Sixtus made him Bishop of Treviso and bestowed numerous other honours upon him. Pietro soon entirely dominated the Pope and from a poor friar became a man of vast wealth. He entered upon an unchecked career of vice, and in two years had squandered a fortune of two hundred thousand gold florins and become a physical wreck. He died in 1472, leaving vast debts which were never paid. Other kinsmen of Sixtus remained laymen but nevertheless were advanced to positions of honour through the influence of the Pope.
On the death of Pietro Riario, Sixtus transferred his affections to his nephew Girolamo, probably also the pontiff’s son, who was called to Rome and given the title to Imola, which had been purchased from Taddeo Manfredi. The government of the States of the Church was entrusted to him, and Galeazzo Sforza conferred upon him the hand of his illegitimate daughter, Caterina, the heroic virago who defended Forli against her husband’s murderers and later against Caesar Borgia, and whom her countrymen styled la prima donna d’Italia. In return for the honour Sixtus made Galeazzo’s son, Ascanio, a cardinal.
Soon after this the Pope succeeded in establishing a matrimonial alliance between his family and the princes of Urbino; for, in return for creating Federico di Montefeltre Duke of Urbino, the latter consented to the marriage of his daughter, Giovanna, to Giovanni della Rovere, another brother of Giuliano.
Sixtus also conferred the purple on Cristoforo and Domenico della Rovere; upon his sister’s son, Geronimo Basso, and also on Raffaele Riario, a nephew of Pietro Riario.
It was stated that the Pope in his eagerness to advance his innumerable kinsmen and connections frequently bestowed an office on one, forgetting he had already given it to another. It was even said that Cardinal Pietro Riario entered into an agreement with Galeazzo Maria Sforza, of Milan, by which the duke was to furnish him with money and troops to enable him to seize the papal throne, which Sixtus appears to have been ready to yield to him; the plan, however, which would have resulted in the secularisation of the Papal States, failed through the death of Pietro.
The secularisation of the Papacy, nevertheless, was proceeding rapidly. The Curia was becoming more and more addicted to the vices of the age. German travellers who visited Rome in 1475, the year of the Jubilee—Paul II. having reduced the period intervening between jubilees to twenty-five years for the sake of the money they yielded—relate that they saw nothing but nepotism, simony, extortion, and crime. On every hand was extravagance, pomp, and vulgar love of display. The populace, as in the days of the Roman Empire, clamoured for spectacular exhibitions, and these the Popes lavishly furnished.
The success of the political schemes of Sixtus demanded the overthrow of the Medici, and he consequently, at least, countenanced the Pazzi conspiracy, which resulted in the murder of Giuliano de’ Medici and the wounding of Lorenzo, who only saved himself by flight. Three weeks later the Pope, King Ferdinand of Naples, and the city of Siena formed a league whose avowed purpose was the expulsion of the Medici from Florence.
Sixtus was a consummate politician, and Infessura speaks of the day on which he died as “that most blessed day upon which God delivered Christendom from the hands of a most impious and iniquitous king.”[6] He states that Sixtus had no affection for his people; that he was avaricious, vain, vicious; that he trafficked in offices and benefices, made a plaything of justice, and that he was cruel and vindictive.
According to history Sixtus was an evil ruler in an evil age. All his acts were inspired by a love of power or an exaggerated affection for his kinsmen. He it was who first completely surrendered the Papacy and Rome to his relatives. He used all sorts of means to increase the Church revenues, only to hand them over to his nephews to use in extending the power of his family. He was, however, not wholly devoid of virtue, for he possessed great learning. Impatient of contradiction, he used any means to overcome opposition, and he soon showed that he was born to rule. Sixtus IV. had none of the priestly characteristics which the Supreme Pontiff is supposed to possess; in him the priest was lost in the prince.