Flavius Josephus, The Wars of the Jews
William Whiston, A.M., Ed.

[115] But as Vespasian had a great mind to fall upon Galilee, he marched out of Ptolemais, having put his army into that order wherein the Romans used to march. He ordered those auxiliaries which were lightly armed, and the archers, to march first, that they might prevent any sudden insults from the enemy, and might search out the woods that looked suspiciously, and were capable of ambuscades. Next to these followed that part of the Romans which was completely armed, both footmen ,and horsemen. Next to these followed ten out of every hundred, carrying along with them their arms, and what was necessary to measure out a camp withal; and after them, such as were to make the road even and straight, and if it were any where rough and hard to be passed over, to plane it, and to cut down the woods that hindered their march, that the army might not be in distress, or tired with their march. Behind these he set such carriages of the army as belonged both to himself and to the other commanders, with a considerable number of their horsemen for their security. After these he marched himself, having with him a select body of footmen, and horsemen, and pikemen. After these came the peculiar cavalry of his own legion, for there were a hundred and twenty horsemen that peculiarly belonged to every legion. Next to these came the mules that carried the engines for sieges, and the other warlike machines of that nature. After these came the commanders of the cohorts and tribunes, having about them soldiers chosen out of the rest. Then came the ensigns encompassing the eagle, which is at the head of every Roman legion, the king, and the strongest of all birds, which seems to them a signal of dominion, and an omen that they shall conquer all against whom they march; these sacred ensigns are followed by the trumpeters. Then came the main army in their squadrons and battalions, with six men in depth, which were followed at last by a centurion, who, according to custom, observed the rest. As for the servants of every legion, they all followed the footmen, and led the baggage of the soldiers, which was borne by the mules and other beasts of burden. But behind all the legions carne the whole multitude of the mercenaries; and those that brought up the rear came last of all for the security of the whole army, being both footmen, and those in their armor also, with a great number of horsemen.