Zosimus, New History 4.07
Zosimus (Greek Ζώσιμος): Early Byzantine, pagan author of a history of the Roman Empire, published in the first quarter of the sixth century CE.
The translation of Zosimus' New History offered here was printed in 1814 by W. Green and T. Chaplin in London, and was probably prepared by J. Davis of the Military Chronicle and Military Classics Office. The translator is anonymous. The text was found at Tertullian.org. The notes were added by Jona Lendering.
[4.7.1] Procopius was so elevated by this fortunate commencement, that his forces considerably augmented, many being of opinion that he was able to contend with the emperors. Both the Roman units and the barbarian troops now flocked to his standard. Besides the reputation of being related to Julian, and of having accompanied him in all the wars he had ever been engaged in, attracted many partisans.
[4.7.2] He likewise sent ambassadors to the chief of Scythia beyond the Ister, who sent to his assistance ten thousand men. The other barbarian nations likewise sent auxiliaries to share in the expedition. Procopius however considered that it would be imprudent in him to engage with both emperors together, and therefore thought it best to advance against him who was nearest, and afterwards deliberate on what course to pursue.
[4.7.3] Thus was Procopius employed; while the emperor Valens, who heard of this insurrection at Galatia in Phrygia, was filled with consternation at the news. Arbitrio having encouraged him not to despair, he prepared the troops that were with him for war, and sent to his brother to inform him of the designs of Procopius.
[4.7.4] Valentinian however was little disposed for sending auxiliaries to one who was incapable of defending the empire committed to his charge. Valens was therefore under the necessity of. preparing for war, and appointed Arbitrio to the command of his army. When the armies were ready to engage, Arbitrio circumvented Procopius by a stratagem, and thereby seduced from him a great number of his men, from whom he received previous information of the designs of Procopius.