Roman citizenship
During the imperial period many Thracians – particularly members of the local aristocracy of the cities – had been granted the right of the Roman citizenship (civitas Romana) with all its privileges. Epigraphic evidence show a large increase in such naturalizations in the times of Trajan and Hadrian, while in 212 AD the emperor Caracalla granted, with his well-known decree (constitutio Antoniniana), the Roman citizenship to all the free inhabitants of the Roman Empire.