THE KINGDOM OF THE ODRISSI
The first Thracian tribe to found its state (beginning of 5th c. B.C.) was that of the Odrysai. They inhabited the vast territories between the Eastern Rhodopes and the Black Sea coast. The first period of the written history of the Odrysai kingdom is connected with the name of the Thracian chief Teres (end of 6th c. B.C. - middle of 5th c. B.C.). According to the ancient Greek philosopher Tuquidid (c. 460 - 404 B.C.), he was not the first ruler but rather the first powerful king of the Odrysai. During the rule of his sons Sparadocus (c. the 50s - 40s of the 5th c. B.C.) and Sitalces (c. the 40s of the 5th c. B. C. - 424 B. C.), and especially his nephew Seuthes I (424 - c. 408/407), the Odrysai planned to conquer the fertile Thracian Hersones (today's Gallipoli Peninsula). The towns of this region paid taxes to the Odrysai and their successors.
In the second half of the 4th c. B.C. the Odrysai kingdom started to decline. Philip II of Macedonia (359 - 336 B.C.) conquered a large part of Thrace. In the place of the old Thracian settlements, situated on today's peak Zaichi near Yambol and today's Nebet Tepe in Plovdiv, he settled military colonists and stationed garrisons. These two towns are known in written sources as Kabile and Philippopolis.
In the 3rd c. B.C. the Odrysai kingdom disintegrated into separate principalities.