Res Gestae

Such was the series of events in Gaul. While they were going on so successfully and so wisely, Constantius sent for Arsaces, king of Armenia, and after entertaining him with the greatest generosity forewarned and urged him to continue to be faithful and friendly to us.

For he heard that he had often been worked upon by the Persian king with deception, with threats, and with guile, to induce him to give up his alliance with the Romans and involve himself in the Persian’s designs.