In 893 Simeon ascended the throne of Bulgaria, becoming Tsar. As a young man this third son of Tsar Boris became a cleric. He traveled to Constantinople where he learned the teachings of the church. Returning home he established a monastery in time for his father to retire. The oldest son Vladimir took his place and immediately reintroduced Tengrism as the state's religion. This polytheistic religion, mired in the roots of Bulgarian history, brought Boris out of retirement. Vladimir was imprisoned and had his eyes gouged out.
Soon thereafter Simeon was brought from the church and placed on the throne. Under his long rule, which laster until 923, the Bulgarians defeated the Magyars of Hungary, the Serbs, and the Macedonians. The routed the Byzantines and for a time lay siege to Constantinople...which was not Istanbul at the time, just to let you They Might Be Giants Fans know. Under Tsar Simeon they ruled a vast, sprawling Empire that last almost a century.