Postumus was Roman emperor from 260 to 269 CE. Marcus Cassianus Latinius Postumus was a trusted military commander of Emperor Gallienus (253-268 CE) and governor or Germania Superior and Inferior (Upper and Lower Germany). After the death of his father Valerian in 260 CE, Gallienus left him in charge of military operations in the west. It was a mistake the inexperienced and trustworthy emperor would soon regret, for the commander's own troops would take advantage of Gallienus's absence to declare Postumus emperor. It was a move that allowed him to establish himself as the ruler of the Gallic Empire, which included Gaul, Spain, and eventually Britain.
More about: Postumus