Commander of the Moesian troops, he obtained an important victory against the invading Goths and was, for this reason, acclaimed Emperor by his army. He then moved quickly to Italy, where he defeated Emperor Trebonianus Gallus, only to be killed by his own men when another general, Valerian, proclaimed himself Emperor and moved against Aemilian with a larger army.
Aemilian was born in the Roman province of Africa. According to the 4th century source Epitome de Caesaribus, he was born at Girba (modern Djerba, an island off the coast of Tunisia) and was a Moor; a reference in the same source hints that he was born around 207. The 12th century historian Joannes Zonaras, who calls him a Libyan (that is, coming from western Egypt-eastern Libya) rather than a Moor, and another chronicle of the 13th century hold that he was forty at the time of his death in 253.
Regarding his lineage, there are two versions, both exaggerated: while Eutropius and his translator Paeanius probably defame a failed usurper when they say that he was from an insignificant family, John of Antioch may refer to Aemilian's propaganda when he says that the usurper used his ancestry to take power. Aemilian married Cornelia Supera, a woman of African origin; the year of their marriage is unknown, but since both were from the same place, it is possible they married before Aemilian left Africa.
During the reign of Trebonianus Gallus and his son Volusianus (251–253), Aemilian was sent to the Balkans to command an army. His primary responsibility was to assure peace along the Danube frontier, which had been subject to several attacks by the Goths led by king Cniva.
Gallus secured the throne after the death of emperor Decius at the hands of Cniva in the Battle of Abrittus (251), and later had to manage an outbreak of plague that devastated Rome. He was not popular with the army, mainly due to humiliating treaties signed in 251 with the Goths and King Shapur I of Persia who attacked Syria. According to John of Antioch, upon his appointment to the Moesian command, Aemilian was already envious of Gallus and plotted treachery against him. He was also an opponent of the Roman Senate, and his seditious plans are confirmed by Jerome and Jordanes.
In 253, the Goths, led by king Cniva, claimed they had not received the tribute due from the Romans according to the treaty of 251. They crossed the border and attacked Cappadocia, Pessinus, and Ephesus. Modern historians believe that this missing payment was not a change in Roman policy, and the Goths were more likely trying to capitalize on their military prowess. Aemilian had command of the army assigned to defend the area, but the recent defeat at the Battle of Abrittus put his troops on edge. Aemilian exhorted them, reminding them of Roman honor (according to Zosimus) and promising tribute from the Goths (according to Zonaras). The Romans took the Goths by surprise, killing most of them, followed by an invasion of Goth territory resulting in booty and the liberation of prisoners. The Roman soldiers, gathered by Aemilian, acclaimed him Emperor. Jordanes claims, however, that Aemilian's troops plundered Roman territory, rather than keep the tribute of the Goths.
With his few men, Aemilian left his province unguarded and moved quickly towards Rome to meet the legitimate emperor Gallus before the latter could receive reinforcements. While Aemilian descended upon Rome along the Flaminian Way, Gallus and Volusianus had him proclaimed "enemy of the State" by the Roman senate, then exited Rome to meet the usurper. This strategy suggests that Aemilian's army was smaller than theirs, as they probably did not expect reinforcements to come in time but trusted their larger army to win the clash. The two armies met at Interamna Nahars (modern Terni), at the southern end of the eastern branch of the Flaminia, and Aemilian won the battle; Gallus and Volusianus fled to the north with a few followers, probably as a delay tactic before the arrival of reinforcements, but at Forum Flaminii (modern San Giovanni Profiamma), on the western branch of Flaminia, they were killed by some of their own guards, who thought that their betrayal could earn them a reward.
Aemilian continued towards Rome. The Roman senate, after a short opposition, decided to recognize him as emperor. According to some sources, Aemilian then wrote to the Senate, promising to fight for the Empire in Thrace and against Persia, and to relinquish his power to the Senate, of which he considered himself a general. Aemilian received the titles of Pius, Felix and Pater Patriae, the tribunicia potestas, and was elevated to the rank of pontifex maximus; he was not, however, elevated to consulate (possibly a hint of his non-senatorial birth). His coinage shows that his propaganda focused on his capability as a military commander—he defeated the Goths when nobody thought this possible, and thus he was the right man for the job of restoring the power of the Roman Empire.
However, Valerian, governor of the Rhine provinces, was on his way south with an army which, according to Zosimus, had been called in as a reinforcement by Gallus. But modern historians believe this army, possibly mobilized for an incumbent campaign in the East, moved only after Gallus' death to support Valerian's bid for power. Emperor Aemilian's men, fearful of a civil war and Valerian's larger force, mutinied. They killed Aemilian at Spoletium or at the Sanguinarium bridge, between Oriculum and Narnia (half way between Spoletium and Rome), and recognized Valerian as the new emperor. After Aemilian's death, which happened between late July and mid-September, a damnatio memoriae against him was declared.
It is possible that the usurper Silbannacus was an officer left by Aemilian in Rome before moving against Valerian, who later tried to become emperor but then was killed.
The troubled administration of emperor Aemilian was perhaps best summed up by Eutropius: