Upon being elected
Pope, Della Rovere adopted the name Sixtus, which had not been used since the 5th century. One of his first acts was to declare a renewed
crusade against the
Ottoman Turks in
Smyrna. However, after the conquest of Smyrna, the fleet disbanded. Some fruitless attempts were made towards unification with the
Greek Church. For the remainder of his pontificate, Sixtus turned to temporal issues and dynastic considerations.
Nepotism , accompanied by his relatives Sixtus IV sought to strengthen his position by surrounding himself with relatives and friends. In the fresco by
Melozzo da Forlì, he is accompanied by his
Della Rovere and
Riario nephews, not all of whom were made cardinals; the
protonotary apostolic Pietro Riario (on his right), the future Pope
Julius II/ Giuliano Della Rovere standing before him; and
Girolamo Riario and
Giovanni della Rovere, behind the kneeling
Platina, author of the first
humanist history of the popes. Pietro died prematurely in 1474. Chroniclers of his life seem to regard his death as unnatural and thus connect his alleged grandiose spending habits and the impression they left on his contemporaries as causal. Criticisms of
Pietro's meteoric rise were not constrained to the charge of benefiting from nepotism as Sixtus IV's nephew, nor to allegations of possibly having been Sixtus IV's illegitimate son. Indeed, Pietro and his brother Girolamo Riario were alleged to have been lovers of Sixtus IV in polemics against the latter. According to the later published chronicle of the Italian historian
Stefano Infessura,
Diary of the City of Rome, Sixtus was a "lover of boys and a sodomite" () awarding benefices and bishoprics in return for sexual favours and nominating a number of young men as cardinals. Sexualised polemics, in truth concerned with politics and not the sexual lives of their victims, were not uncommon during this time; but as
Pfisterer (sic) notes "the novel flood of accusations of sodomy against a pope" and "true flood of corresponding lampoons, reviling poems, and fictional epitaphs" following his death are at the very least evidence for his contemporaries' opinions about the promotions of these young men. The secular fortunes of the Della Rovere family began when Sixtus invested his nephew
Giovanni with the lordship of
Senigallia and arranged his marriage to the daughter of
Federico III da Montefeltro, duke of
Urbino; from that union came a line of Della Rovere dukes of Urbino that lasted until the line expired, in 1631. Six of the thirty-four cardinals that he created were his nephews. In his territorial aggrandizement of the
Papal States, his niece's son, Cardinal
Raffaele Riario (for whom the
Palazzo della Cancelleria was constructed) was suspected of colluding in the failed
Pazzi conspiracy of 1478 to assassinate both
Lorenzo de' Medici and his brother
Giuliano and replace them in
Florence with Sixtus IV's other nephew,
Girolamo Riario.
Francesco Salviati,
Archbishop of Pisa and a main organizer of the plot, was hanged on the walls of the Florentine
Palazzo della Signoria. Sixtus IV replied with an
interdict and two years of war with Florence. However, Infessura had partisan allegiances to the
Colonna and so is not considered to be always reliable or impartial. The English churchman and
Protestant polemicist
John Bale, writing a century later, attributed to Sixtus "the authorisation to practice
sodomy during periods of warm weather" to the "Cardinal of Santa Lucia". This prompted the noted historian of the Catholic Church,
Ludwig von Pastor, to issue a firm rebuttal.
Foreign policy Sixtus continued a dispute with King
Louis XI of France, who upheld the
Pragmatic Sanction of Bourges (1438), which held that papal decrees needed royal assent before they could be promulgated in France.
Slavery The two papal bulls issued by
Pope Nicholas V,
Dum Diversas of 1452 and
Romanus Pontifex of 1455, had effectively given the Portuguese the rights to acquire non-Christian slaves along the African Coast by force or trade. Those concessions were confirmed by Sixtus in his own bull,
Aeterni regis, of 21 June 1481. Arguably the "ideology of conquest" expounded in those texts became the means by which commerce and conversion were facilitated. In November 1476, Isabel and Fernando ordered an investigation into rights of conquest in the Canary Islands, and in the spring of 1478, they sent Juan Rejon with sixty soldiers and thirty cavalry to the Grand Canary, where the natives retreated inland. Sixtus's earlier threats to excommunicate all captains or pirates who enslaved Christians in the bull
Regimini Gregis of 1476 could have been intended to emphasise the need to convert the natives of the
Canary Islands and
Guinea and establish a clear difference in status between those who had converted and those who resisted. The ecclesiastical penalties were directed towards those who were enslaving the recent converts.
Princely patronage As a civic patron in Rome, even the anti-papal chronicler Stefano Infessura agreed that Sixtus should be admired. The dedicatory inscription in the fresco by
Melozzo da Forlì in the
Vatican Palace records: "You gave your city temples, streets, squares, fortifications, bridges and restored the
Acqua Vergine as far as the
Trevi..." In addition to restoring the aqueduct that provided Rome an alternative to the river water, which had made the city famously unhealthy, he restored or rebuilt over 30 of Rome's dilapidated churches such as
San Vitale (1475) and
Santa Maria del Popolo, and he added seven new ones. The
Sistine Chapel was sponsored by Sixtus IV, as was the
Ponte Sisto, the
Sistine Bridge (the first new bridge across the
Tiber since Antiquity), and the building of
Via Sistina (later named ''Borgo Sant'Angelo''), a road leading from
Castel Sant'Angelo to Saint Peter. All of that was done to facilitate the integration of the
Vatican Hill and
Borgo with the heart of Old Rome. That was part of a broader scheme of
urbanization carried out under Sixtus IV, who swept the long-established markets from the
Campidoglio in 1477 and decreed in a bull of 1480 the widening of streets and the first post-Roman paving, the removal of porticoes and other post-classical impediments to free public passage. , the first bridge built at Rome since the
Roman Empire At the beginning of his papacy, in 1471, Sixtus had donated several historically important Roman sculptures that founded a papal collection of art, which would eventually develop into the collections of the
Capitoline Museums. He also refounded, enriched and enlarged the
Vatican Library. and increased the size and prestige of the papal chapel choir, bringing singers and some prominent composers (
Gaspar van Weerbeke,
Marbrianus de Orto and
Bertrandus Vaqueras) to Rome from the north. In addition to being a patron of the arts, Sixtus was a patron of the sciences. Before he became pope, he had spent time at the very liberal and cosmopolitan
University of Padua, which maintained considerable independence from the Church and had a very international character. As Pope, he issued a
papal bull allowing local bishops to give the bodies of executed criminals and unidentified corpses to physicians and artists for dissection. It was that access to corpses which allowed the anatomist
Vesalius, along with
Titian's pupil
Jan Stephen van Calcar, to complete the revolutionary medical/anatomical text
De humani corporis fabrica.
Other activities Consistories The Pope created 34 cardinals in eight consistories held during his reign, among them three nephews, one grandnephew and one other relative, thus continuing the practice of nepotism that he and his successors would engage in during this period.
Canonizations and beatifications Sixtus IV named seven new saints, with the most notable being
Bonaventure (1482); he also beatified one person, John Buoni (1483).
Uppsala University In 1477, Sixtus IV issued a
papal bull authorizing the creation of
Uppsala University – the first university in
Sweden and in the whole of
Scandinavia. The choice of this location for the university derived from the fact that the
archbishopric of Uppsala had been one of the most important
sees in
Sweden proper since Christianity first spread to this region in the ninth century, as well as Uppsala being long-standing hub for regional trade. Uppsala's bull, which granted the university its corporate rights, established a number of provisions. Among the most important of these was that the university was officially given the same freedoms and privileges as the
University of Bologna. This included the right to establish the four traditional faculties of
theology, law (
Canon Law and
Roman law), medicine, and philosophy, and to award the bachelor's, master's, licentiate, and doctoral degrees. The archbishop of Uppsala was also named as the university's
Chancellor, and was charged with maintaining the rights and privileges of the university and its members. This act of Sixtus IV had a profound long-term effect on the society and culture of Sweden, an effect which continues up to the present. ==Death==