The Battle of the Bosnian Highlands is fought between the huge armies of the two Balkan rulers of the time: Bulgarian Tsar Simeon I, the great victor of the Battle of Anchialus over the Byzantine Empire ten years earlier, and King Tomislav of Croatia, the first king of the Croatian state.According to Theophanes Continuatus (The Continuer of Theophanes's Chronicle) and other historians, the battle takes place on May 27, 927 and is fought in the area of the highlands of Eastern Bosnia near the Drina River, the border area between the Kingdom of Croatia and the Bulgarian Empire.The Bulgarian ruler, Simeon, is a wise and able man with a restless and insatiable spirit.

He spends his entire life fighting battles with neighboring countries.

His basic aim is to defeat the Byzantine Empire and conquer Byzantium.

To achieve his aim, Simeon overruns the eastern and central Balkans several times, occupies Serbia and finally attacks Croatia.