Postumus (Marcus Cassianius Latinius), Gallienus' military commander on the Rhine from AD 259, quarrelled with the young prince Saloninus [son of Gallienus] and his civilian advisers during the barbarian attacks following the capture of Valerian (260). He seized power and established himself a Roman emperor in Gaul, Britain and Spain. He defended his 'Gallic empire' against both Germanic invaders and Gallienus (26 8) . . .