Roman imperial transport and communication system. It was ultimately derived from that of the Achaemenian empire, which was probably established in the 6th century BC by Cyrus the Great (Cyrus II). The angaria system, like the word, was presumably passed down to the Romans through the Hellenistic kingdoms. In the developed Roman system, to supply the means of transport was a compulsory duty of communities and citizens along the route; exemption, when granted by the emperor, was a major benefaction. The word thus came to mean a tax or compulsory service. It was later applied to an animal or carriage used in the system.