<P> The most influential decision in the reign of Pope Gregory XI (1370--1378) was the return to Rome, beginning on 13 September 1376 and ending with his arrival on 17 January 1377 . Although the Pope was French born and still under strong influence by the French King, the increasing conflict between factions friendly and hostile to the Pope posed a threat to the papal lands and to the allegiance of Rome itself . When the papacy established an embargo against grain exports during a food scarcity 1374 and 1375, Florence organized several cities into a league against the papacy: Milan, Bologna, Perugia, Pisa, Lucca and Genoa . The papal legate, Robert of Geneva, a relative of the House of Savoy, pursued a particularly ruthless policy against the league to re-establish control over these cities . He convinced Pope Gregory to hire Breton mercenaries . To quell an uprising of the inhabitants of Cesena he hired John Hawkwood and had the majority of the people massacred (between 2,500 and 3,500 people were reported dead). Following such events opposition against the papacy strengthened . Florence came in open conflict with the Pope, a conflict called "the war of the eight saints" in reference to the eight Florentine councilors who were chosen to orchestrate the conflict . The entire city of Florence was excommunicated and as reply the export of clerical taxes was stopped . The trade was seriously hampered and both sides had to find a solution . In his decision about returning to Rome, the Pope was also under the influence of Catherine of Siena, later canonized, who preached for a return to Rome . </P> <P> This resolution was short - lived, however, when, having returned the papal court to Rome, Pope Gregory XI died . A conclave met and elected an Italian pope, Urban VI . Pope Urban alienated the French cardinals, who held a second conclave electing one of their own, Robert of Geneva, who took the name Clement VII, to succeed Gregory XI, thus founding a second line of Avignon popes . Clement VII, along with his successors are not regarded as legitimate, and are referred to as antipopes by the Catholic Church . This situation, known as the Western Schism, persisted from 1378 until the ecumenical Council of Constance (1414--1418) resolved the question of papal succession and declared the French conclave of 1378 to be invalid . A new Pope, Pope Martin V, was elected in 1417; other claimants to succeed to the line of the Avignon Popes (though not resident at Avignon) continued until c. 1437 . </P> <P> The period has been called the "Babylonian captivity" of the popes . When and where this term originated is uncertain although it may have sprung from Petrarch, who in a letter to a friend (1340--1353) written during his stay at Avignon, described Avignon of that time as the "Babylon of the west," referring to the worldly practices of the church hierarchy . The nickname is polemical, in referring to the claim by critics that the prosperity of the church at that time was accompanied by a profound compromise of the papacy's spiritual integrity, especially in the alleged subordination of the powers of the Church to the ambitions of the French kings . As noted, the "captivity" of the popes at Avignon lasted about the same amount of time as the exile of the Jews in Babylon, making the analogy convenient and rhetorically potent . The Avignon papacy has been and is often today depicted as being totally dependent on the French kings, and sometimes as even being treacherous to its spiritual role and its heritage in Rome . </P> <P> Almost a century and a half later, Protestant reformer Martin Luther wrote his treatise On the Babylonian Captivity of the Church (1520), but he claimed it had nothing to do with the Western Schism or papacy in Avignon . </P>

The avignon popes may have strengthened their control over the church