Leo X was the last of the Renaissance popes before the dawn of the Reformation, but his role in the indulgence controversy left the indelible impression of his pontificate. Born Giovanni de’Medici in Florence on December 11, 1475, he was the second son of Lorenzo the Magnificent, patriarch of the powerful mercantile Medici family that had by the fifteenth century become prominent bankers and Florentine politicians. Leo’s father set him on a course to ecclesiastical service at an early age. He was named apostolic protonotary in 1483 and cardinal deacon of Santa Maria in Dominica in 1489. He received the best of humanist education in his father’s house, the most prominent of his tutors being Marsilio Ficino and Pico della Mirandola. After studying theology and canon law at Pisa between 1489 and 1492, he took up residence as cardinal in Rome. He would return to Florence later that year after the death of his father and live with his older brother, Pietro, until the family was exiled in 1494 as a result of the uprising spearheaded by Girolomo Savanarola.

The tumultuous exile of the Medicis from Florence led the young cardinal to travel across the Europe of his day, visiting France, Holland, and Germany between 1494 and 1500, which exposed him to the flourishing Renaissance humanism outside of Italy. When his brother Pietro died in 1503, Leo became the head of the Medici family and soon took a central role in Italian politics. He was named legate of Bologna and Romagna in October 1511, which left him in charge of the papal forces there. He was imprisoned in Ravenna in 1512 by the French, but escaped and would help reestablish the Medicis in Florence with a peaceful revolution that ended their exile on September 14, 1512. The course of events established Leo as an adroit political mind and made him a candidate for the papal tiara vacated when the reigning pontiff, Julius II, died on February 21, 1513. A conclave opened on March 4 to choose a replacement. Composed of 25 cardinals—excluding the nine associated at the time with the council in Pisa—the conclave selected Leo in part because the older cardinals believed his recurrent ill health would lead to a short tenure and in part because his political wherewithal might help Rome drive the Spanish and the French out of papal lands in Naples and Milan. Leo was elected on March 11 at the age of 37. His reign proved far from peaceful, as evidenced by the fact that several cardinals hatched a plot to poison him in 1517, for which one was killed, numerous others imprisoned, and the Roman curia filled with new cardinals supportive of his rule.

The primary electoral capitulation Leo made was to bring to completion the Fifth Lateran Council, which his predecessor had convened in 1512. Lateran V began in opposition to a rival council in Pisa, which was convoked under the leadership of nine dissident cardinals and supported by French royalty and clergy. Julius designated it a conciliabalum, or “pseudo-council,” and under pressure called a council of his own in Rome. There were numerous goals for the Lateran council, including the healing of the Pisan schism, eradication of heresy, pacification of Christian princes at odds with Rome, preparation of a crusade, and the general reform of Christendom, specifically that of the papacy, cardinals, and curia. In March 1514, Leo published a bull, Supernae dispositionis arbitrio, addressing the reform of the curia, but never sought to enforce its measures. He carried the council through to its end on March 16, 1517.

One significant outcome of Lateran V brokered by Leo was the end to the Pragmatic Sanction of Bourges. A measure taken in 1438 at the height of the conciliar controversy to insure administrative and fiscal independence for the French church in exchange for its support of then-pope Eugenius IV against the Council of Basel, the Pragmatic Sanction had caused continual tensions between Rome and France. During the course of the council, Leo negotiated a plan that would give the French king the right to nominate all French bishops, abbots, and priors, while granting the pope the prerogative of naming all vacant French benefices in the curia as well as other French-related benefices. The new agreement was reached in the 1516 Concordat of Bologna, ratified by the council six months later with the bull Primitiva, and would remain in effect until the 1780 French Revolution.

As pontiff, Leo became known for his patronage of the arts in Renaissance Rome and the luxurious lifestyle associated with it. He infamously said, “God has given us the papacy, let us enjoy it.” Under his tenure, Leo continued the project of rebuilding St. Peter’s Basilica, begun under Julius II, and commissioned famed Renaissance artists Michelangelo and Raphael for the task. Raphael was also charged with decorating the pontifical palaces and painting the tapestries in the Sistine Chapel. In addition to his role as purveyor of art, Leo spared no expense in collecting rare books, manuscripts, and gems. He enjoyed hunting and would take an extensive papal entourage with him to join in the activities. The papal household itself was quite large and cost upwards of 100,000 ducats a year. His expenditures exhausted the papal treasury and put it 400,000 ducats in debt by the end of his pontificate.

Leo’s reign saw the start of the Reformation as a result of his handling of the indulgence controversy. Due to the debt associated with his pontificate, the Medici pope had been unable to commit sufficient resources to Julius’s project of rebuilding St. Peter’s. When the archbishopric of Mainz became available and Albrecht of Brandenburg sought the see, Leo saw an opportunity to resume the St. Peter’s project by authorizing the sale of indulgences in Albrecht’s territories. Half of the proceeds would go to repaying Albrecht’s debt to the Fugger bankers for the loan he needed to purchase the see, while the other half would go to rebuilding St. Peter’s. In 1515, Leo renewed the decree authorizing the sale of indulgences first published by his predecessor. As a result, Albrecht commissioned the noted preacher of indulgences, Leipzig Dominican John Tetzel, to proclaim the sale and it was Tetzel whom Luther chiefly targeted in the 1517 95 Theses.

Upon receiving an opinion of the theses from the faculty at Mainz, Albrecht filed charges against Luther with Rome. The investigation into Luther’s teaching began in summer 1518, when Leo’s court summoned the Augustinian monk and Wittenberg professor to answer for himself, before sending Cardinal Cajetan to interview Luther in Augsburg. Leo directed Cajetan to seize Luther and bring him to Rome, though Frederick the Wise persuaded Cajetan to relent. The proceedings against Luther would resume again in earnest in 1519 after Leo published a bull, Cum postquam, that rejected Luther’s criticisms of the papal authority to grant indulgences. Later that year at Leipzig, Luther came to denounce papal authority in the church and the papal decretals supporting it, leading to an escalation of the controversy.

The 95 Theses did not directly attack Leo, but they did call into question the right of the papacy to grant indulgences, a point that Luther’s opponents repeatedly raised in their rejoinders. Luther sought to distract attention from the question of papal authority, even dedicating his explanation of the theses on indulgences, the 1518 Resolutiones, to the pope himself. In response to the diplomatic efforts of Karl von Miltitz, a papal chamberlain, Luther agreed to write a letter to the sitting pope expressing remorse for the indulgence affair, which he drafted in 1519 but never sent. A year later, Miltitz prevailed upon Luther to try one last time to mend the breach with Leo by sending him a conciliatory letter, attached to the 1520 treatise The Freedom of a Christian. The so-called “Open Letter to Leo X,” composed in German rather than Latin and intended for popular publication, directed blame for the affair at the Roman curia, which Luther believed to be manipulating the pope and not to have the church’s best interests in mind.

Leo’s court finally brought Luther to the point of condemnation in 1520, when it published the bull Exsurge Domine threatening him with excommunication if he did not appear in Rome within sixty days and recant of his teachings. The bull detailed a list of 41 errors, largely enumerated by Luther’s Leipzig combatant, John Eck, and was received in Wittenberg in October. On December 10, in accordance with the deadline stipulated, Luther and the Wittenberg students burned the bull along with the books of canon law in a symbolic gesture of defiance. Leo then followed through with the threat of excommunication in the January 1521 bull Decet Romanum pontificem, a judgment that would lead to Luther’s trial at Worms in April 1521 and his declaration by Charles V as a heretic and outlaw in the May 1521 Edict of Worms.

Leo would die of pneumonia later that year on December 1 and was buried in Santa Maria Sopra Minerva. The legacy he left behind would remain permanently connected with his failures to stint the Reformation. His pontificate did not bring about the reforms anticipated by Lateran V, but instead deepened the fiscal and political problems in Rome. This precipitated the decision to authorize the sale of indulgences that stimulated the onset of the Reformation. His attempt to prosecute Luther’s teaching on indulgences and ultimately to excommunicate him did not eradicate Lutheran doctrine, but instead further splintered the Western church.