Pope Pelagius II confirms Grado as the new metropolitan see of the ecclesiastical province of Venetia et Histria; 11th-century forgery.
Pope Pelagius II writes to Helias, the patriarch of Aquileia, and all the bishops of Istria, the province whose prelates still persevered in their refusal to condemn the three chapters denounced by the Fifth Ecumenical Council (Constantinople II) of 553, urging them to desist from their schismatic ways and return to the embrace of the Catholic Church.
Pope Gregory I writes to Severus, the patriarch of Aquileia, requesting on behalf of the emperor (Maurice) that he come to Rome with his clergy and be judged on a synod (for his unwillingness to condemn the Three Chapters and his perseverance in supporting the schism).
Pope Gregory I writes to Callinicus, the Exarch of Italy, regarding a variety of affairs, including the recent military victory over the Slavs and the return of the Church of Koper to the Catholic creed.
Pope Gregory I writes to Maxim, the bishop of Salona, on a variety of matters, including the latest advances of the Slavs and their recent incursions into Italy by way of Istria.
Pope Honorius incites all the bishops of the ecclesiastical province Venetia et Histria to profess disobedience to the deposed patriarch Fortunatus of Grado and to accept subdeacon Primogenius, to whom the pope had already sent the pallium, as their new lawful head of the ecclesiastical province; moreover, the pope promises to open diplomatic negotiations with the Lombard king, with whom the deposed Fortunatus sought refuge, with the goal of restoring all the ecclesiastical goods stolen by the said Fortunatus.
Pope John IV dispatches abbot Martin to journey across Dalmatia and Istria to ransom the captives (imprisoned, one would assume, by the still pagan Slavs) and return the relics of the saints from these endangered places to Rome; narrative account from the Book of the Popes (Liber pontificalis).
Pope Adrian I writes to Charlemagne, the King of the Franks and the Lombards, beseeching him to direct Duke Marcarius of Friuli to help reinstate the Istrian bishop Maurice – whose eyes have been gouged out by “the most abominable Greeks” – to his bishopric.
Emperor Charlemagne subordinates six episcopal sees to the Church of Aquileia, badly damaged by the incursions of the pagans; late-10th-century forgery.
Pope Sergius IV confirms the jurisdictions of the bishops of Poreč over Rovinj, Dvigrad, and Bale that were disputed by the Aquileian patriarch John.
Henry, the incumbent patriarch of Aquileia, pledges his oath of fealty to Pope Gregory VII.
Pope Gregory VII formally bequeaths to Henry, the patriarch of Aquileia, the right to don the pallium even on the feast days of St. Ulrich and St. Afra as compensation for the help he had provided to the papal legates, the bishops of Padua and Albano.