Legio III Diocletiana

III Diocletiana was created when Diocletian reorganized Egypt in 298. The new legion was to guard Alexandria, together with II Traiana Fortis; it was logical that if there was already a second legion, the new unit would have the number three.

In the fourth century, it became clear that stronger forces were needed in southern Egypt, and units of III Diocletiana were sent to Thebes and Kom Ombo. During the reign of Theodosius I (378-395), northern barbarians were sent as legionaries to Egypt and served in III Diocletiana, whereas Egyptian soldiers were sent to Macedonia. They were called III Diocletiana Thebaeorum and served under the military commander of Thrace.