Zosimus, New History 3.16

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 ZosimusNew 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.

[3.16.1] They proceeded from thence to a branch of the Euphrates, which reaches as far as Assyria and joins the Tigris.note Here the army found a stiff clay and marshy ground, in which the horses could not move without difficulty. As they could not swim across the river in their armor, nor ford through it being deep and full of mud, they did not know how to extricate themselves. 

[3.16.2] Their difficulties were increased by the appearance of the enemy on the opposite bank, who were prepared to obstruct their passage with darts and stones, which they threw with slings. When no other person could imagine an expedient to free them from those imminent dangers, the emperor himself, who had great sagacity in all things, and was well versed in military affairs, determined on ordering Lucilianus and his reconnoitring party to make an attack on the enemy's rear, and thereby create a diversion, until the army had crossed the river.

[3.16.3] For this purpose he sent Victor, with a competent number of men. He began his journey in the night, that the enemy might not discover him, and when he had proceeded so far that the enemy could not perceive him even in the day, he crossed the channel to seek Lucilianus and his party.