Late Roman Army during the 5th century

[Nathan Ross]

The Fabricae were not mentioned at all until the late 4th century

Lactantius claimed that Diocletian set up the first armorum fabrica in Nicomedia; John Malalas also notes that Diocletian established fabricae in Edessa, Antioch and Damascus. Papyrii from Egypt suggest one or more arms factories there in c.298. The tetrarchic senator Attius Tertullus is described in an inscription (CIL VI, 1696) as praefectus fabricae, which might also refer to arms factories in Italy.

So it would appear that most of the fabricae in the east were established by Diocletian; those in the west most probably date from Constantine.