Pope (1271-1276). Tedaldo Visconti was an archdeacon of Liège on pilgrimage in Outremer when he was elected pope in 1271. His predecessor, Clement IV, had died on 29 November 1268, and the interval that followed constituted the longest vacancy in papal history. Gregory’s election occurred only because St. Bonaventure and the mayor of Viterbo locked the cardinals in a palace on a diet of bread and water until they elected a pope. The length of Gregory’s journey back from Outremer to Rome further delayed his coronation until 27 March 1272.
Because his predecessors had succeeded in obliterating the political power of the Staufen emperors, Gregory was free to develop his plans for the reunion of the Greek Orthodox and the Latin churches; in his eyes, this was necessary for a new crusade and the protection of Outremer. While still in Outremer, Gregory wrote a letter to the Byzantine emperor Michael VIII Palaiologos expressing his interest in opening negotiations for union. Once in Rome, the new pope called for a council to be held in Lyons to discuss union with the Orthodox, a new crusade, and reform of the church.
The council opened on 7 May 1274. The Orthodox delegation sent by the Byzantine emperor was small but was authorized to accept Latin definitions of papal authority, purgatory, and the procession of the Holy Spirit. Gregory demanded that the Byzantines fully accept Latin teaching but acknowledged that it would take time for change to take place. Although some Orthodox theologians were interested in Latin theology, much of the Byzantine interest in union was predicated on the belief that it would prevent Western attacks on the empire.
Gregory overturned previous papal support for Charles I of Anjou, king of Sicily, seeing his growing influence in northern Italy as a threat to papal independence. This furthermore pleased the Byzantines, for an invasion by Charles was one of the threats the Byzantine emperor feared the most. Gregory’s planned crusade never materialized, mainly as a result of European conflicts that lessened monarchical interest in joining the crusade. Gregory died on 10 January 1276 in Arezzo.