Introduction

The textual sources for the military and political relationship between Rome and Sasanian Persia in the third and fourth centuries come from a range of different genres, languages and timeframes. It provides only brief coverage of the conflict between Sasanian Persia and Rome in the third and fourth centuries. The three kingdoms or principalities that lay between the Caucasus Mountains and the kingdom of Armenia were Colchis, Iberia and Albania. Armenia's geographical location and topography was of key importance to the military and political relationship between Rome and Persia and ensured that the kingdom was the focus of intense competition in both the Parthian and Sasanian periods. With the directional flow of the Tigris running west-east as it flowed out of ancient Armenia, the river played an important defensive role in the fourth century before it turned to flow south into Adiabene and then on to Assyria and southern Mesopotamia.