Legio II Flavia Constantia
II Flavia Constantia was formed together with I Maximiana to garrison the newly created province Thebaid which became part of the new diocese of Aegyptus, this province faced south against the enemies the Romans, such as the Nubians, Kush, Meroe and Axum. The name of the legion is related to Constantius Chlorus, who was one of the four emperors at the time of the tetrarchs.
II Flavia Constantia had its headquarters in Cusas (Not. Or. XXXI) until the time of the Notitia Dignitatum. In the course of time, probably under Constantine I, when the troops of the Egyptian provinces were united under the command of a dux (CIL II 12073), the legionary troops of the province were increased with units from both legions of Aegyptus I Iovia, II Traiana, and III Diocletiana, the latter gradually being divided into three garrisons (Not. or. XXXI 31. 33. 38).
II Flavia Constantia Thebaeorum, which belonged, at the time of the Notitia, to the comitatus of the magister militum per Orientem (Not. or. VII 10 = 45), was certainly a split off from II Flavia Constantia, which was, for more than a century, an established border-legion. The impulse for this split was probably given by a measure of Theodosius I, to mix a part of the Barbarians, which were passed over to him, with the troops in Egypt. These barbarians were added to the Egyptian troops and their accompanying commander in Macedonia (Zosimus IV 30 and 31), who resided at that time in Thessalonica. A part of II Flavia Constantia belonged to these Aiguptioi (Egyptians). It is fitting that at this time the legion II Flavia Valentis Thebaeorum (Not or. VII 11 = 46), which accompanied the troops in the Notitia and was named after and probably raised by Emperor Valens, was no longer mentioned with the garrison of Thebaidos (Not. or. XXXI), because of the short time it stayed in the province.