Thracia used to be in the borders of modern Bulgaria, Greece and Turkey. Thracia was populated by the indigenous Thracian people. Their country was known as Odrysian kingdom.
It was the year 20 BC when Rhoemetalces, Thracian king, made Odrysian kingdom a Roman client state. Following the death of Rhoemetalces, an upraising againt the Roman overlords took place. This resulted with the complete annexation of the Odrysian kingdom and turned Thracia into a complete Roman province.
Heraclea Perinthus became the first capital of the Roman province of Thracia. One of the most major trade routes of the Roman civilization, Via Egnatia, passed through Tracia, making the province prosperous. Thracia shrank in size during the rule of emperor Diocletian. Province of Thracia was divided into four smaller provinces and the new capital became Philippopolis.