Zosimus, New History 2.51
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.
[2.51.1] Constantius, considering that as this was a civil war victory itself would be scarcely an advantage to him, now the Romans being so much weakened, as to be totally unable to resist the barbarians who attacked them on every side, began to think that it would be better to end the war by offering proposals for peace.
[2.51.2] While he was thus deliberating, the armies were still engaged and that of Magnentius became more furious, nor would they cease fighting though night came on, but even their officers continued performing what belonged to common soldiers, and encouraging their men to oppose the enemy with vigor.
[2.51.3] On the other side likewise, the officers of Constantius called to mind the ancient bravery and renown of the Romans. Thus the battle continued until it was completely dark, nor did even darkness cause them to relax, but they wounded each other with spears, swords or whatever was in their reach, so that neither night nor any other obstacle which usually causes some respite in war, could put an end to the slaughter, as if they thought it the greatest felicity that could happen to them to perish beside each other.
[2.51.4] Amongst the officers, that showed great bravery in this battle and fell in it were Arcadius, commander of the unit called Abulci, and Menelaus, who commanded the Armenian horse archers.