Simeon I, c.863–927, ruler (893–927) and later first czar of Bulgaria. He was placed on the throne by his father, Boris I, who had returned from a monastery to depose his first son, Vladimir (reigned 889–93), for attempting to reintroduce paganism. Simeon, ambitious to conquer a vast empire, made duties levied on Bulgarian trade a pretext for attacking the Byzantine emperor Leo VI. Simeon defeated Leo but was defeated in turn by Leo's allies, the Magyars under Arpad. However, aided by the Pechenegs, he drove the Magyars into their present domain in Hungary. Simeon ravaged the Byzantine Empire, threatened Constantinople several times, and temporarily held Adrianople. He conquered most of Serbia and took (925) the title czar of the Bulgars and autocrat of the Greeks, which was approved (926) by Pope John X. Denying the supremacy of the patriarch at Constantinople, he raised the archbishop of Bulgaria to the rank of patriarch. At his capital, Preslav, Simeon held a court of unprecedented splendor. Under his rule the first Bulgarian empire attained its greatest power, and Church Slavonic literature reached its golden age. An able Greek scholar, Simeon fostered the translation of Greek works into Church Slavonic. During the reign of his son and successor, Peter, the empire was destroyed by internal dissension and foreign attacks.