Ammianus Marcellinus Res Gestae 21.11.2

[2] Two of Constantius’ legions, which with one cohort of bowmen he had found at Sirmium, being not yet sure of their loyalty he had sent to Gaul under colour of urgent necessity. These were slow to move, through dread of the long march and of the Germans, our fierce and persistent foes, and were planning a rebellion, aided and abetted by Nigrinus, a native of Mesopotamia and commander of a troop of horsemen. Having arranged the plot by secret conferences and added to its strength by profound silence, on arriving at Aquileia, a well-situated and prosperous city, surrounded by strong walls, with hostile intent they suddenly closed its gates, supported in this revolt by the native population, because of the dread which was even then connected with the name of Constantius. ¹