GALLIENUS (Publius Licinius Egnatius Gallienus)
- Gallienus was the son of Publius Licinius Valerianus (Valerian I) and Egnatia Mariniana.
- When his father became emperor in 253, Gallienus was named Caesar but almost immediately was raised to the rank of Augustus and joint ruler.
- In 254 Valerian left for the east to fight the Persians, leaving Gallienus in charge of the west.
- From 254 to 258 Gallienus campaigned mainly on the Danube.
- Gallienus's eldest son, P. Cornelius Licinius Valerianus (Valerian II), was made Caesar in 254, but died early in 258. In his place, his younger brother, Cornelius Saloninus Valerianus was appointed as Caesar, in 259 as Augustus.
- In 259 the Juthungi crossed the Upper Danube and invaded Italy, but were defeated at Milan.
- In 260, Valerian was capured and a consequence was that several rebellions against Gallienus errupted: by Ingenuus, governor of Pannonia and Moesia, by Regalianus on the Danube, by Fulvius Iunius Macrianus and his younger brother Fulvius Iunius Quietus in the east and by Aureolus, Gallienus's main commander.
- In addition groups of germanic tribes, Alemanni and Franks were ravaging Europe. This gave the opportunity for Marcus Cassianius Latinius Postumus, the governor of Lower Germany, to make a bid for power.
- Postumus was proclaimed emperor by his soldiers, and beseiged Colonia Agrippina, where Saloninus, now Augustus, was holed-up. Saloninus was handed over and Postumus had him put to death.
- By 261 Postumus was recognised as emperor in Gaul, Britain and Spain.
- While Gallienus dealt with usurpers in the west, his praetorian commander, Ballista was able to fight off the Persians, even capturing Shapur's harem. He was aided by Odenathus of Palmyra who re-occupied Mesopotamia for Rome.
- In 266 Odenathus defeated the Persians at Ctesiphon and then advanced into Asia Minor to defeat an invasion by the Goths. However, he was then murdered by some of his own party and Gallienus sent a force against the Palmyrenes.
- The following year, the Palmyrenes defeated the Roman general whom Gallienus sent against them and control of the east went to Zenobia, widow of Odenathus, and their young son Vaballathus.
- In 268 there were large scale invasions into the Balkans by the Goths, aided by the Heruli from the Black Sea area. Although Athens was sacked, the invaders were defeated in battle at Naissus.
- At the same time Gallienus's cavalry commander, Aureolus, had defected to Postumus. Gallienus returned to Italy in September 268, defeated Aureolus at Pontirolo and laid siege to him at Milan.
- Before Gallienus could end the seige, he was murdered by a group of his own officers.