text: By the end of the 4th century BC, Greek language and culture were dominant not only in the Balkans but also around the whole Eastern Mediterranean. In the late 6th century BC, the Persians invaded the Balkans, and then proceed to the more fertile areas of Europe. Parts of the Balkans and more northern areas were ruled by the Achaemenid Persians for some time, including Thrace, Paeonia, Macedon, and most Black Sea coastal regions of Bulgaria, Romania, Ukraine, and Russia. However, the outcome of the Greco-Persian Wars resulted in the Achaemenids being forced to withdraw from most of their European territories.
  The Thracian Odrysian kingdom was the most important Thracian state union. It was founded c.470 BC after the Persian defeat in Greece, had its capital at Seuthopolis, near Kazanlak, Stara Zagora Province, in central Bulgaria. Other tribal unions existed in Dacia at least as early as the beginning of the 2nd century BC under King Oroles. The Illyrian tribes were situated in the area corresponding to today's Adriatic coast. The name Illyrii was originally used to refer to a people occupying an area centered on Lake Skadar, situated between Albania and Montenegro (Illyrians proper). However, the term was subsequently used by the Greeks and Romans as a generic name for the different peoples within a well defined but much greater area. In the same way, the territory to the north of the kingdom of Macedon was occupied by the Paeonians, who were also ruled by kings.
  Achaemenid Persian Empire (6th to 5th century BC)