The three chief candidates considered by historians are Illyrian, Dacian, or Thracian, though there were other non-Greek groups in the ancient Balkans, including Paionians (who lived north of Macedon) and Agrianians.
Acting on this intelligence, Alexander awaited the arrival of night, and then rushed ahead without awaiting the crossing of his complete force, leading his shield-bearing guards, the Agrianians, archers and the brigade of Coenus as the leading unit.