Byzantine–Bulgarian wars: Bulgarian forces led by Tsar Simeon I drove the Byzantines out of Thrace with a decisive victory at the Battle of Achelous. Simeon I of Bulgaria: Simeon I the Great was the ruler of the First Bulgarian Empire from 893 until his death in 927. Simeon's successful campaigns against the Byzantines, Magyars and Serbs led Bulgaria to its greatest territorial expansion ever, making it the most powerful state in contemporary Eastern and Southeast Europe. His reign was also a period of unmatched cultural prosperity and enlightenment later deemed the Golden Age of Bulgarian culture. August 20, 917. Wiki link