The Roman philosopher Lucian demanded that history be written by someone who “at some point has been in a camp and has seen soldiers exercising or drilling and knows about weapons and ma chinery” (How to write history 37). As far as the Roman army’s order of march is concerned, the handful of descriptions that have survived were indeed written by men who, in Lucian’s words, “know what ‘in column’ and ‘in line’ mean”.
We can dispense with the military manuals of Onasander and Vegetius. Although they mention the subject, they remind us of the type of historians Lucian warns us against: “the ones who stay at home or who rely only on what they have been told” (How to write history 37). Fortunately, we have two prime eyewitnesses: Josephus and Arrian.
Between them, these writers describe a campaigning Roman army on three different occasions - Vespasian’s invasion of Galilee in AD 67, Titus’ advance on Jerusalem in AD 70, and Arrian’s own expedition to meet the marauding Alans in AD 136 -, 2000) generalises from the examples of Titus and Arrian: “Firstly, the vanguard was normally made up of auxiliaries and cavalry; they were to explore the terrain and to retreat if necessary. Similarly, the rear-guard was usually formed by less important units. Lastly, as a rule, the baggage was placed in the middle to receive maximum protection; this was the army’s weak spot when on the march.”
