Publius Licinius Egnatius Gallienus was born in about AD 213.
Compared to other Roman emperors of the age, Gallienus was an exception, as far as he was not a soldier-emperor. He was rather a thoughtful, intellectual ruler, possessing sophisticated Greek tastes. However, this made him deeply unpopular with the gritty Danubian generals, who very much understood it as their right to choose a leader among their own ranks to rule the empire.
His father handed him responsibility over the western provinces, while he would take the fight east to the Persians. Though the two should never meet again, as Valerian fell into the hands of the enemy and died in captivity.
If the Danubian military elite didn't like Gallienus, then he certainly soon proved that he was a capable military leader. Between AD 254 to AD 256 he campaigned along the Danube, securing this troubled frontier against the barbarians. In AD 256 he then moved west to fight the Germans along the Rhine.
Seeking to continue the dynasty of his father, Gallienus raised his eldest son Licinius Valerianus to the rank of Caesar in early AD 256. But when in AD 258 the emperor returned to the Danube to renew his struggles with the barbarians there, his heir died. In his place, his brother Salonius was raised to be Caesar.
Then, in AD 259, the chaos began which was to haunt Gallienus throughout his reign. Gallienus was still fighting along the Danube, when message reached him that further west the Juthungi (Jutes) and the Alemanni had crossed the river a were descending into Italy.
But this success cannot disguise what was a desperate situation for Gallienus. The Franks were attacking in large numbers, crossing the Rhine and forcing their way into Gaul. Some even reaching as far as Tarraco (Tarragona) on the Mediterranean coast. Some even getting on boats, crossing the Mediterranean and raiding the north African coast, including the port of Tingitana.
Then by autumn AD 260 the dreadful message of Valerian's capture by the Persians reached Gallienus. If Gallienus had always been unpopular among the military leaders, then now with his father gone and Roman authority crumbling, rebellion was in the air.
The first to act was Ingenuus, the powerful governor of Pannonia. He had himself hailed emperor at Sirmium, by the troops of Pannonia and Moesia. Though these armies were merely the remaining garrison of the two provinces, as most were campaigning with the emperor. With such limited support Ingenuus was soon defeated at Mursa in Pannonia by the returning Gallienus and his general Manius Acilius Aureolus.
With Gallienus occupied with Regalianus, the command of the Rhine armies was left to Marcus Cassianius Latinius Postumus, governor of Lower Germany, with the emperor's son Saloninus, guarded by the praetorian prefect Silvanus, staying at Colonia Agrippina (Cologne).
But in late AD 260 yet another serious rebellion took place. Had the capture of emperor Valentinian left the defences of the east in utter turmoil. Antioch fell to the advancing Persians. Until two generals, Macrianus and Callistus (whose nickname was 'Ballista'), rallied what was left of Roman troops and defeated the Persian king Sapor at Corycus, halting his advance and forcing him to withdraw back behind the Euphrates.
Of these two Roman generals Macrianus now decided the time was right to challenge Gallienus' rule. Though, knowing himself to old, he nominated not himself but his two sons, Fulvius Iunius Macrianus and his and Fulvius Iunius Quietus, as emperors of the east, with Antioch as their capital.
Gallienus found a rare ally in Odenathus, the very powerful prince of Palmyra, granting him command of the armies in the east. At once Odenathus attacked Quietus, the remaining rebel, at Emesa and defeated him.
The death of Quietus only saw yet another pretender to the throne arise, as Mussius Aemilianus, the governor of Egypt, who had supported Macrianus and Quietus, now had himself hailed emperor. But in AD 262 he, too, was defeated by general Theodotus and executed.
Also in AD 262, Odenathus launched a five year campaign against the Persians, re-conquering much of Mesopotamia and Armenia.
In the west Gallienus, having gained back at least some limited control over his territories, set out to crush Postumus in the spring of AD 265, advancing deep into Gaul.
In the east, after outstanding victories against the Persians - most of all defeating the Persians at Ctesiphon in AD 266 -, Odenathus was awarded the title of imperator by Gallienus.
But Gallienus himself was to have far greater problems to deal with than either the Palmyrene queen Zenobia, or the 'Gallic' emperor Postumus.
Having perhaps saved the empire from oblivion, Gallienus could have dealt the Goths a shattering blow by hunting down and defeating their remaining forces.
But Gallienus was not to gain victory over Aureolus. The Danubian military elite had finally had enough of the emperor they had never liked. A plot was hatched among the praetorian prefect Heraclianus and a group of high ranking commanders. Among these officers were the future emperors Claudius Gothicus and Aurelian.
And so on a night in September AD 268, at the siege of Mediolanum, the alarm was suddenly raised in the camp of the emperor. In the brief moment of confusion, Gallienus was struck down in the dark as he emerged from his tent.
As a last gesture of disrespect to this, most unfortunate of emperors, the Romans should lay Gallienus to rest not in one of the great mausoleums in Rome, but in a tomb nine miles south of the capital, along the Via Appia.