Many problems confronted Leo X. on his accession. He had to preserve the papal conquests which he had inherited from Alex ander VI. and Julius II., to minimize foreign influence, whether French, Spanish or German, in Italy to put an end to the Pisan schism and to settle the other troubles incident to the French invasion. Other outstanding problems were the restoration of the French Church to Catholic unity, and the settlement of the wranglings of the German humanists. At the time of Leo's accession Louis XII. of France, in alliance with Venice, was attempting to regain the duchy of Milan and the pope, after fruitless endeavours to maintain peace, joined the league of Mechlin on April 5, 1513, with the emperor Maximilian I., Ferd inand I. of Spain and Henry VIII. of England. The French and Venetians were at first successful, but on June 6 they were de feated at Novara. The Venetians continued the struggle until October. On Dec. 19 the fifth Lateran council, reopened by Leo in April, ratified the peace with Louis XII., and registered the con clusion of the Pisan schism. While the council was planning a crusade and considering the reform of the clergy, a new crisis occurred between the pope and the king of France. Francis I., who succeeded Louis XII. on Jan. 1, 1515, was intent on recover ing Milan and Naples. Leo formed a new league with the em peror and the king of Spain, and, to ensure English support, made Wolsey a cardinal. Francis entered Italy jet August and won the battle of Marignano (Sept. The pope in October signed an agreement binding him to with draw his troops from Parma and Piacenza, on condition of French protection at Rome and Florence. He held a secret conference with Francis at Bologna in Dec. 1515. The ostensible subjects under consideration were the establishment of peace between France, Venice and the Empire, with a view to an expedition against the Turks, and the ecclesiastical affairs of France. Pre cisely what was arranged is unknown.
During these two or three years of incessant intrigue and war fare the Lateran council was seriously hampered. Its three main objects, the peace of Christendom, the crusade and the reform of the church demanded general agreement among the powers which was lacking. Its most important achievements were the registra tion at its eleventh sitting (Dec. 19, 1516) of the abolition of the pragmatic sanction, which the popes since Pius II. had unani mously condemned, and the confirmation of the concordat between Leo X. and Francis I., which was to regulate the relations be tween the French Church and the Holy See until the Revolution. Leo closed the council on March 16, 1517. It had ended the schism, ratified the censorship of books introduced by Alexander VI. and imposed tithes for a war against the Turks. It raised no voice against the primacy of the pope.
Leo had practised nepotism from the beginning. His cousin Giulio (later Clement VII.), was made archbishop of Florence, cardinal and vice-chancellor of the Holy See. Leo had named his younger brother Giuliano and his nephew Lorenzo, Roman patri cians; he had placed Lorenzo in charge of Florence; he married Giuliano to Filiberta of Savoy, and intended to carve out a kingdom for him in Central Italy. After the death of Giuliano in March 1516, Leo transferred his ambitions to Lorenzo. At the
very time (Dec. 1516) that peace between France, Spain, Venice and the Empire seemed to give some promise of a Christendom united against the Turk, Leo was preparing an enterprise against the duke of Urbino. He obtained 150,00o ducats from Henry VIII. of England, in return for which he entered the imperial league of Spain and England against France. The war lasted from Feb. to Sept. 1517, and ended with the expulsion of the duke and the triumph of Lorenzo ; but it increased brigandage and anarchy in the States of the Church, hindered the preparations for a crusade and wrecked the papal finances. Leo now took advantage of a plot of several of the members of the sacred college to poison him, to execute one cardinal, imprison several others, and to make a radical change in the college. On July 3, 1517, he published the names of 35 new cardinals, among whom were such as Lorenzo Campeggio, Giambattista Pallavicini, Adrian of Utrecht, Cajetan, Cristoforo Numai and Egidio Canisio.
Leo meanwhile was planning a crusade to prevent the advance of Selim I. A truce was to be proclaimed throughout Christen dom ; the pope was to be the arbiter of disputes ; the emperor and the king of France were to lead the army ; England, Spain and Portugal were to furnish the fleet ; and the combined forces were to be directed against Constantinople. Papal diplomacy in the interests of peace failed, however ; Cardinal Wolsey made Eng land, not the pope, the arbiter between France and the Empire; and much of the money collected for the crusade from tithes and indulgences was spent in other ways. In 1519 Hungary concluded a three years' truce with Selim I., but the succeeding sultan, Suli man the Magnificent, renewed the war in June 1521, and cap tured the citadel of Belgrade. Leo treated the Uniate Greeks with great loyalty, and by bull of May 18, 1521, forbade Latin clergy to celebrate mass in Greek churches and Latin bishops to ordain Greek clergy. These provisions were later strengthened by Clement VII. and Paul III. and went far to settle the chronic disputes between the Latins and Uniate Greeks.
Leo was disturbed throughout his pontificate by heresy and schism. The dispute between Reuchlin and Pfefferkorn was re ferred to the pope in Sept. 1513. He in turn referred it to the bishops of Spires and Worms, who gave decision in March in favour of Reuchlin. After the appeal of the inquisitor-general, Hochstraten, and the appearance of the Epistolae obscurorumv virorum, however, Leo annulled the decision (June 152o) and im posed silence on Reuchlin. The pope had authorized the extensive grant of indulgences to secure funds for the crusade and for the rebuilding of St. Peter's at Rome. Against the attendant abuses the Augustinian monk Martin Luther (q.v.), posted (Oct. 31, 1517) on the church door at Wittenberg his famous ninety-five theses, which were the signal for widespread revolt against the church. Leo directed (Feb. 3, 1518) the vicar-general of the Augustinians to impose silence on the monks. On Aug. 7 Luther was cited to appear at Rome. The citation was cancelled, how ever, and Luther betook himself in October 1518 to Augsburg to meet the papal legate, Cardinal Cajetan. Fruitless negotiation followed, during which the pamphlets of the reformer set all Germany on fire.