Симеон I
By the late 9th and early 10th centuries, Bulgaria extended to Epirus and Thessaly in the south, Bosnia in the west and controlled all of present-day Romania and eastern Hungary to the north reuniting with old roots. A Serbian state came into existence as a dependency of the Bulgarian Empire. Under Tsar Simeon I of Bulgaria (Simeon the Great), who was educated in Constantinople, Bulgaria became again a serious threat to the Byzantine Empire. His aggressive policy was aimed at displacing Byzantium as major partner of the nomadic polities in the area. By subverting the principles of Byzantine diplomacy and political culture, Simeon turned his own kingdom into a society-structuring factor in the nomadic world.