Roman emperors

The papacy and Christianised Germanic kingdoms of the West acknowledged the Eastern emperors until the accession of Empress Irene in 797. After this, the papacy created a rival lineage of Roman emperors in western Europe, the Holy Roman Emperors, which ruled the Holy Roman Empire for most of the period between 800 and 1806. These emperors were never recognized in Constantinople and their coronations resulted in the medieval problem of two emperors. The last Eastern emperor was Constantine XI Palaiologos, who died during the Fall of Constantinople to the Ottoman Empire in 1453. After conquering the city, Ottoman sultans adopted the title "Caesar of the Romans" (kayser-i Rûm). A Byzantine group of claimant emperors existed in the Empire of Trebizond until its conquest by the Ottomans in 1461, although they have used a modified title since 1282.