Pax Nicephori, Latin for the "Peace of Nicephorus", is a term used to refer to both a peace treaty of 803, tentatively concluded between the Frankish rulerCharlemagne and the Byzantine emperorNikephoros I, and the outcome of negotiations that took place between the same parties, but were concluded by successor emperors, between 811 and 814. The whole set of negotiations of the years 802–815 has also been referred to by this name. By its terms, after several years of diplomatic exchanges, the Byzantine emperor's representatives recognized the authority in the West of Charlemagne, and East and West negotiated their boundaries in the Adriatic Sea.
Though Nikephoros always refused to recognize Charlemagne's imperial title, envoys of the East and West made agreements over the possession of disputed Italian territory, namely, the provinces of Venetia and Dalmatian Croatia, during the first decade of the ninth century. These seem to have been advantageous to the Venetians and to have guaranteed Byzantine sovereignty over them.
Temporary shift of Venetian loyalties toward the Franks resulted in somewhat permanent naval conflict in the Adriatic, only interrupted by a truce in 807–808. After Charlemagne's son and king of Italy Pippin's invasion of Dalmatia tension rose between the two Empires. Political and military instability, however, lasted only until the king's death, in July 810. Then a new treaty came under discussion between Charlemagne, temporarily ruling over Italy, and Nikephoros. Aigone, Count of Forlì, was a member of the delegation sent by Charlemagne to Nikephoros. The agreement was signed. Thus the name pax Nicephori may be justifiably applied to this second episode of diplomatic activity. However, only Michael I Rhangabes recognized Charlemagne's imperial title, reserving for the East the title "Emperor of the Romans", and the treaty was not definitely ratified until four years later, after both Michael's and Charlemagne's death, by Louis the Pious and Leo V. Some amendments, more advantageous to Venice, are thought to have been added then. The peace of Aachen in 812 confirmed Dalmatian Croatia, except for the Byzantine cities and islands, as under Frankish domain. The boundaries in Dalmatia imposed by this treaty were unclear, so in 817 Leo V sent en embassy to Aachen to clarify them. The result was a joint Frankish and Byzantine expedition to Dalmatia to get the input of the local Romans and Slavs and firmly delimit the borders.
Buffer states
The common belief that the negotiations between Byzantium and the Franks that were held in the early ninth century made Venice an 'independent polity' is only based on the late, allusive and biased witness of Venetian chroniclers such as John the Deacon and Andrea Dandolo and remains therefore highly questionable.
