Publius (or Flavius) Vegetius Renatus, known as Vegetius (u̯ɛˈɡɛtiʊs), was a writer of the Later Roman Empire (late 4th century). Nothing is known of his life or station beyond what is contained in his two surviving works: Epitoma rei militaris (also referred to as De re militari), and the lesser-known Digesta Artis Mulomedicinae, a guide to veterinary medicine. He identifies himself in the opening of his work Epitoma rei militaris as a Christian.
The latest event alluded to in his Epitoma rei militaris is the death of the Emperor Gratian (383); the earliest attestation of the work is a subscriptio by Flavius Eutropius, writing in Constantinople in 450, which appears in one of two families of manuscripts, suggesting that a division of the manuscript tradition had already occurred. Despite Eutropius' location in Constantinople, the scholarly consensus is that Vegetius wrote in the Western Roman Empire. Vegetius dedicates his work to the reigning emperor, who is identified as Theodosius, ad Theodosium imperatorem, in the manuscript family that was not edited in 450; the identity is disputed: some scholars identify him with Theodosius I (, while others follow Otto Seeck and identify him with the later Valentinian III, dating the work to 430–35. Goffart agrees that the later date is likely, suggesting that the work may have been intended to support a military revival in the time of Aetius's supremacy. Rosenbaum also argues that he wrote in the early 430s; Theodosius II might then have been the dedicatee. Rosenbaum uses allusions from Vegetius's works and relationships to the work of Merobaudes to suggest that Vegetius was a senior court official, primiscrinius to the praetorian prefect, who had been an agens in rebus.
De re militari
Vegetius' epitome mainly focuses on military organization and how to react to certain occasions in war. Vegetius explains how one should fortify and organize a camp, how to train troops, how to handle undisciplined troops, how to handle a battle engagement, how to march, formation gauge and many other useful methods of promoting organization and valour in the legion.