Since we’re talking about Gregory XI, let’s check the historical background:
In 1375, Florence came in open conflict with Pope Gregory XI (reign 1370-1378). The causes of this war are rooted in interrelated issues: Florentine opposition to the expansion of the Papal States in central Italy (which the
Avignon Popes, of whom Gregory was one, had set as a condition for their return) and antipathy toward the
Guelphs in Florence. Specifically, the city feared in the autumn of 1372 that Gregory intended to reoccupy a strip of territory near Lunigiana, which Florence had conquered from
Bernabò Visconti, Lord of Milan, and that the illustrious Ubaldini family might switch from Florentine to Papal allegiance.
Gregory also harbored various grievances against Florence for their refusal to directly aid him in his war against the House of Visconti. When Gregory’s war against Milan ended in 1375, many Florentines feared that the pope would turn his military attention toward Tuscany; thus, Florence paid off Gregory XI’s main military commander,
condottiero John Hawkwood (1320-1394), with 130,000 florins, extracted from local clergy, bishops, abbots, monasteries, and ecclesiastical institutions, by an eight-member committee appointed by the
Signoria.
Eventually, Florence formed an alliance with Milan in July 1375, immediately prior to the outbreak of the war, and the prosecution of the war was entirely delegated to an eight-member committee appointed by the Signoria, the
otto della guerra (“eight of war”). It was after this committee that this three-year period war was named: the
War of the Eight Saints.
Florence incited a revolt in the Papal States in 1375. Florentine agents were sent to more than forty cities in the Papal States—including Bologna, Perugia, Orvieto, and Viterbo—to foment rebellion, many of which had only been re-submitted to papal authority by the efforts of Cardinal
Gil Álvarez Carrillo de Albornoz (1310-1367). Chancellor of Florence
Coluccio Salutati (1331-1406) even disseminated public letters urging the cities to rebel against the “tyrannical” and “corrupt” papal rule.
The Catholic Encyclopedia adds that many people were already restless because of Gregory’s “
fatal mistake of appointing Frenchmen, who did not understand the Italians and whom the Italians hated, as legates and governors of the ecclesiastical provinces in Italy.” They only needed someone to stir them up.
Reacting to this uprising, Gregory excommunicated all members of the government of Florence and placed the city under interdict on March 31, 1376, banning religious services in Florence and legalizing the arrest and enslavement of Florentines and the confiscation of their property throughout Europe. One of the results of the ban is that Florentine merchants were hurt economically throughout Europe, particularly the
Alberti bankers in Avignon, although the interdict was ignored by many, including Charles V of France.
Originally, Florentines made no effort to oppose the ban, organising extra-ecclesiastical processions (including flagellants) and confraternities, the edifice of the Florentine inquisition was destroyed and the Signoria roled back legal restrictions on usury and other practices frowned on by the now defunct ecclesiastical courts. However, on October 1377, the government of Florence forced the clergy to resume religious services causing Angelo Ricasoli, Bishop of Florence, and Neri Corsini, Bishop of Fiesole, to flee from Florentine territory. The heavy fines and confiscations issued by the Signoria on prelates who left their posts, the “
most extensive liquidation of an ecclesiastical patrimony attempted anywhere in Europe before the Reformation,” may have been motivated to pay for the increasingly expensive conflict.
John Hawkwood honored his agreement with the Florentines not to make war in Tuscany, limiting himself to putting down the various rebellions within the Papal States; however, in 1377 Hawkwood abandoned Gregory entirely and joined the anti-papal coalition. Gregory XI’s other
condottieri also limited their acitivities to Romagna, notably sacking Cesena in February 1377. In the spring of 1377, papal mercenaries recaptured Bologna, which up until that point had been a key Florentine ally. In 1377,
Cardinal Robert of Geneva (1342-1394) led Gregory’s army in an attempt to quell the revolt, and Gregory himself returned to Italy to secure his Roman possessions under the influence of St. Catherine of Siena, de facto ending the Avignon Papacy. Gregory arrived in Rome in January 1378, after a difficult journey (including shipwreck), and died there in March 1378. The war eventually ended with a peace treaty concluded at Tivoli in July 1378, negotiated with
Urban VI following Gregory’s death and with the beginning of the Western Schism (1378-1417).