POSTUMUS (Marcus Cassianius Postumus)
- Postumus came from Gaul (probably a Batavian), although his age and birthplace are not known.
- He was governor of Lower Germany, when he was proclaimed emperor by the Rhine legions early in the autumn of 260, after Valerian's capture by the Persians.
- He captured and executed Gallienus's son, Saloninus at Colonia Agrippina (Cologne).
- Gallienus, with plenty of other problems decided to leave Postumus alone until he had settled matters on the Danube front.
- Postumus meanwhile restored the defences of the Rhine frontier and the damage done by the Frankish and Alemannic invasions of 260.
- The "Gallic" empire thus formed by Postumus, consisted of the provinces of Gaul (Lugdunensis, Aquitania and Narbonensis) and upper and lower Germany. By 261, Britain and Spain had also gone over to Postumus.
- In 265, Gallienus, with the aid of his general, Aureolus, attempted to win back the lost provinces but after some successes, abondoned the idea when he was wounded in battle.
- In 268 Aureolus defected to Postumus, but Postumus failed to back him up.
- Postumus outlived Gallienus, just.
- Late in 268, came news of a rebellion of Laelianus, overnor of Upper Germany (under Postumus) at Mainz.
- Postumus soon defeated the usurper and retook Mainz. But Postumus refused to allow his soldiers to pillage the city, and was murdered by them.