Gallienus

Gallienus (c. 218–268), son of Valerian, ruled the West as Augustus from 253 while his father held the East, and routed the Alemanni near Mediolanum in 259.

Valerian's capture at Edessa in 260 made him sole emperor and plunged the empire into civil war. He overthrew the eastern usurpers but could not stop Postumus founding the Gallic Empire, and his son Saloninus was killed by Postumus' army.

His 260 edict granted Christians their first imperial toleration, and he built a cavalry field army. In 268 he was killed in an officers' plot while besieging a rebel at Mediolanum.