It was shortly after that, though, that the powerful Romans were making their presence seen on the Balkans. The Romans had a hard time subordinating the brave Thracians, they only managed to conquer the lands of some Thracian tribes and put them under submission. The Odrysian Kingdom, however, was resisting the initial pressure from the Romans and with some diplomatic moves, the Odrysians were able to preserve their independence. For example, around 168 BC the Odrysians became allies to the Roman Empire and were fighting on its side, even against other Thracian tribes. The Odrysian influence spread even into the internal political struggles in Rome. The Odrysians were actively involved in the Roman civil wars during the reigns of Julius Cesar, Octavian August and Mark Antonius. The latter even officially recognized the sovereignty of the Odrysian kings.
Thus, through this recognition of sovereignty and close ties, the Odrysians were slowly assimilated into the Roman Empire and were becoming Roman citizens. This strategy worked well for the Romans because around 46 AD all Thracian lands, including the Odrysian kingdom, were referred to as a Roman province – the province of Thrace.