It was established by Postumus in 260 in the wake of barbarian invasions and instability in Rome, and at its height included the territories of Germania, Gaul, Britannia, and (for a time) Hispania. After Postumus' assassination in 269 it lost much of its territory, but continued under a number of emperors and usurpers. It was retaken by Roman emperor Aurelian after the Battle of Châlons in 274.