Zosimus, New History 2.15
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.
[2.15.1] Meantime Constantine, who had long been jealous of him, was then much more disposed to contention. Having therefore raised an army amongst the barbarians, Germans, and Celts, whom he had conquered, and likewise drawn a force out of Britain, amounting in the whole to ninety thousand foot and eight thousand horse, he marched from the Alps into Italy, passing those towns that surrendered without doing them any damage, but taking by storm those which resisted.
[2.15.2] While he was making this progress, Maxentius had collected a much stronger army; consisting of eighty thousand Romans and Italians, all the Tuscans on the sea coast, forty thousand men from Carthage, besides what the Sicilians sent him; his whole force amounting to a hundred and seventy thousand foot and eighteen thousand horse.
[2.15.3] Both being thus prepared, Maxentius threw a bridge over the Tiber, which was not of one entire piece, but divided into two parts, the centre of the bridge being made to fasten with irons, which might be drawn out upon occasion.
[2.15.4] He gave orders to the workmen, that as soon as they saw the army of Constantine upon the juncture of the bridge, they should draw out the iron fastenings, that the enemy who stood upon it might fall into the river.