Zosimus, New History 4.31
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.
[4.31.1] When the Egyptians arrived in Macedonia, and were united with the units there, no order was observed in the camp, nor was any distinction made between a Roman and a barbarian, but all were promiscuously mingled together, nor was even a muster-roll kept with the names of the soldiers. It was likewise permitted to the barbarians to return to their own country, and to send others in lieu of themselves to serve in the armies, and when they pleased, again to serve under the Romans.
[4.31.2] The barbarians on learning the disordered state of the army, of which the fugitives informed them, and of the free access they had to it, thought this a convenient opportunity to make an attempt against the Romans, who conducted their affairs so negligently.
[4.31.3] Having therefore passed the river without difficulty, they penetrated as far as Macedonia without opposition, since the fugitives suffered them to proceed unmolested. Perceiving that the emperor was advancing to meet them with all his forces, and being guided at midnight by a large fire which they conjectured to be near his person, and likewise understood to be so from the countrymen who deserted to them, they assaulted the emperor's tent.
[4.31.4] Being now joined by their countrymen, they were opposed by the Romans and Egyptians alone. These being comparatively a small number could only enable the emperor to escape, but were themselves nearly all slain, after having fought courageously and killed a great number of the barbarians.
[4.31.5] Had the barbarians followed up their advantage, and pursued those who fled with the emperor, they would certainly have had them all immediately in their power. But being satisfied with what they had gained, and having made themselves masters of Macedonia and Thessaly, which were without protection, they left the towns uninjured, in hopes of receiving a tribute from them.