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 who had previously been 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 towards 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 conflicts under Alexander Severus, and in the victorious Battle of Rhesaena 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 records it at the beginning of the 5th century, stationed at Apatna in Osroene, evidence of its long-standing loyalty to the eastern theater of the Roman Empire.