Legio III Parthica Roman Vexillum

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

The expedition concluded with the capture and sacking of Ctesiphon, after which the legion remained permanently in the East to garrison the new province of Mesopotamia. Its main base camp was Rhesaena, along the Chaboras, with the task of controlling communication routes to the Euphrates and confronting first the Parthians, then the Sasanids.

In the 3rd century, the III Parthica participated in Caracalla's campaigns against the Parthians (216-217), in clashes under Alexander Severus, and in the victorious Battle of Resaena during Gordian III's war against the Sasanids. Despite mutinies and the upheavals of the period, the legion continued to operate as a frontier force, progressively becoming a Mesopotamian limitanea unit. The Notitia Dignitatum still mentions it in the early 5th century, stationed at Apatna in Osroene, evidence of its long fidelity to the eastern theater of the Roman Empire.