Charlemagne

The iconoclasm of the Isaurian Dynasty and resulting religious conflicts with the Empress Irene, sitting on the throne in Constantinople in 800 C.E., were probably the chief causes of Pope Leo's desire to formally resurrect the Roman imperial title in the West. He also most certainly desired to increase the influence of the papacy, to honor Charlemagne, who had saved him, and to solve the constitutional issues then most troubling to European jurists in an era when Rome was not in the hands of an emperor. Thus, Charlemagne's assumption of the title of Caesar Augustus, Constantine, and Justinian was not an usurpation in the eyes of the Franks or Italians. However, in Greece it was strongly protested by Empress Irene and the usurper Nicephorus I, neither of whom had any great effect in enforcing their protests.

The Byzantines, however, still held several territories in Italy: Venice (what was left of the exarchate of Ravenna), Reggio (Calabria, the toe), Brindisi (Apulia, the heel), and Naples (the Ducatus Neapolitanus). These regions remained outside of Frankish hands until 804 C.E., when the Venetians, torn by infighting, transferred their allegiance to the Iron Crown of Pippin, Charles' son. The Pax Nicephori ended. Nicephorus ravaged the coasts with a fleet and the only instance of war between Constantinople and Aachen, as it was, began. It lasted until 810, when the pro-Byzantine party in Venice gave their city back to the emperor in Byzantium and the two emperors of Europe made peace. Charlemagne received the Istrian peninsula and in 812 C.E. Emperor Michael I Rhangabes recognised his title.