Legio III Parthica Roman Standard

Legio III Parthica was created by Septimius Severus in AD 197 for the great campaign against the Parthian Empire, together with its sister legions I and II Parthica, recruited largely from Syrian conscripts formerly loyal to Pescennius Niger.

The expedition ended with the capture and sack of Ctesiphon, after which the legion remained permanently in the East to garrison the new province of Mesopotamia. Its main base was Rhesaena, on the Chaboras, tasked with controlling the routes towards the Euphrates and confronting first the Parthians and then the Sasanians.

In the 3rd century III Parthica took part in Caracalla’s campaigns against the Parthians (216‑217), in the clashes under Severus Alexander and in the victorious battle of Resaena in Gordian III’s war against the Sasanians. Despite mutinies and the upheavals of the period, the legion continued to operate as a frontier force, gradually becoming a Mesopotamian limitanea unit. The Notitia Dignitatum still records it in the early 5th century, stationed at Apatna in Osroene, proof of its long loyalty to the eastern theatre of the Roman Empire.