Zosimus, New History 2.50
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.
[2.50.1] Meanwhile Magnentius approached nearer to Mursa, and set fire to the gates, thinking if he could destroy the iron that covered the wood, which would soon yield to the flames, he might make a passage wide enough for the entrance of his army into the city. But this did not succeed to his wishes, the people on the wall extinguishing the flames with water which they poured down in large quantities. When he therefore heard that Constantius was near Mursa, he invented another stratagem to this effect.
[2.50.2] There was before the city a stadium or place of exercise, formerly used by those that fought for prizes, which was covered over with wood. In this he concealed four companies of Celtae, with orders when Constantius should come up, and they were ready to engage before the city, to attack the enemy by surprise, and to surround them and kill every man. This being discovered by those that were on the walls, Constantius immediately sent thither Scolidon and Manadus, two of his officers.
[2.50.3] They first selected the choicest of their men, both heavy armed and archers, and taking them along with themselves, fastened up all the doors of the stadium. Having then possessed themselves of the upper steps leading into the stadium, and inclosed the soldiers that were within on all sides, they threw darts at them. And observing some of them with their shields placed over their heads attempting to force open the doors, they fell upon them and did not cease throwing darts or cutting at them with their swords until they had killed them all.
[2.50.4] This project of Magnentius being thus frustrated, the armies met and engaged in the plain before Mursa, where such a battle was fought as had not occurred before in the course of this war, and great numbers fell on both sides.