According to Eutropius and Aurelius Victor, he was particularly energetic and successful in preventing invaders from attacking the German provinces and Gaul, despite the weakness caused by Valerian's march on Italy against Aemilianus in 253.
During his Danube sojourn (Drinkwater suggests in 255 or 256), he proclaimed his elder son Valerian II Caesar and thus official heir to himself and Valerian I; the boy probably joined Gallienus on campaign at that time, and when Gallienus moved west to the Rhine provinces in 257, he remained behind on the Danube as the personification of Imperial authority.
He then hastily crossed the Balkans, taking with him the new cavalry corps (comitatus) under the command of Aureolus The victory must be attributed mainly to the cavalry and its brilliant commander.
Ingenuus was killed by his own guards or committed suicide by drowning himself after the fall of his capital, Sirmium.
Coins struck for them in major cities of the East indicate acknowledgement of the usurpation.
The two Macriani left Quietus, Ballista, and, presumably, Odenathus to deal with the Persians while they invaded Europe with an army of 30,000 men, according to the Historia Augusta. The Pannonian legions joined the invaders, being resentful of the absence of Gallienus.
Sometime between 258 and 260 (the exact date is unclear), while Valerian was distracted with the ongoing invasion of Shapur I in the East, and Gallienus was preoccupied with his problems in the West, Ingenuus, governor of at least one of the Pannonian provinces, Ingenuus may have been responsible for that calamity.
Alternatively, the defeat and capture of Valerian at the battle of Edessa may have been the trigger for the subsequent revolts of Ingenuus, Regalianus, and Postumus. He left his son Saloninus as Caesar at Cologne, under the supervision of Albanus (or Silvanus) and the military leadership of Postumus.
It took a rally by an officer named Callistus (Balista), a fiscal official named Fulvius Macrianus, the remnants of the Roman army in the east, and Odenathus and his Palmyrene horsemen to turn the tide against Shapur.
The invasion occurred probably in the early spring of 260.
The Roman army was defeated at the Battle of Edessa, and Valerian was taken prisoner.
While he won a number of military victories, he was unable to prevent the secession of important provinces.
His 15-year reign was the longest since the 19-year rule of Caracalla. The Greek chronicler John Malalas and the Epitome de Caesaribus report that he was about 50 years old at the time of his death, meaning he was born around 218.