During the persecution of Diocletian, St. Crescentianus, a Roman knight, and ten others suffered martyrdom at Tifernum. The bishopric was erected circa 450 AD. In 550, Fantalogus, by order of the Ostrogothic king Totila, took and destroyed the city then known as Tifernum or Civitas Tiberina. Città di Castello was later rebuilt around a castle, giving origin to the name used today. At the time of the sack of the city by Fantalogus, the bishop was Florius, later a friend of Gregory the Great. In 590 the diocese of Tifernum gained territory from the suppressed Diocese of Sant'Angelo in Vado. By the Donation of Pepin, it became subject to the Holy See. It lost territories in 1013, to establish the Territorial Abbey of Sansepolcro, and on 19 June 1325 to establish the Diocese of Cortona. The first-known bishop of this see was Ennodius, present at a Roman council under Pope Hilary. In 711 ArianLongobardsput to death the bishop of the city, Albertus, and his deacon Britius. In 875 Bishop Rainaldus was summoned to appear before the papal apocrisiarius Gregory and the magister militum Georgius, the vestiarius of the Patriarch of Aquileia, to answer a charge of homicide. Having failed to deal with the situation, despite several letters of excommunication, Rainaldus was summoned by Pope John VIII to appear in Rome and stand trial. Rainaldus appeared at the papal court, but stealthily avoided taking his seat in the synod, and instead fled the city by going over the walls like a thief. Revealing himself to be guilty, he was immediately excommunicated and interdicted. The Pope announced the result in a letter to the Emperor Louis. Pope Celestine II was a native of Città di Castello. In 1375 Città di Castello joined in the insurrection of other cities of the Papal States. Cardinal Robert of Geneva, undertook to recapture it with Breton mercenaries, but was repulsed. Under Pope Martin V, however, it was taken by Braccio da Montone. Later, Nicolò Vitelli, with the help of Florence and Milan, became absolute ruler. In 1474 Pope Sixtus IV sent there his nephew, CardinalGiuliano della Rovere. After fruitless negotiations he laid siege to the city, but Vitelli did not surrender until he learned that the command of the army had been given to Duke Federigo of Urbino. The following year Vitelli tried unsuccessfully to recapture the city; fear of Cesare Borgia alone induced him to desist. On 22 September 1515 it lost more territory to the Territorial Abbey of Sansepolcro.
Synods
A diocesan synod was an irregular but important meeting of the bishop of a diocese and his clergy. Its purpose was to proclaim generally the various decrees already issued by the bishop; to discuss and ratify measures on which the bishop chose to consult with his clergy; to publish statutes and decrees of the diocesan synod, of the provincial synod, and of the Holy See. Bishop Giovanni Battista Lattanzi held his first diocesan synod on 23–25 September 1766. Bishop Francesco Antonio Mondelli held a diocesan synod on 8–10 April 1818. Bishop Giovanni Muzi held a diocesan synod on 1 June 1835. Letterio Turchi held a diocesan synod on 14–16 June 1853.
