Vetranio

Vetranio (died c. 356 AD) was briefly a imperial usurper and emperor in the Roman Empire in 350, during which time he controlled Illyricum between the rival emperors Magnus Magnentius and Constantius II, eventually capitulating to the latter.

Early life
Vetranio was born in the Roman province of Moesia to low-born parents, sometime in the late 3rd century. His early professions are unknown, but it is evident that at some point he joined the military and must have greatly distinguished himself to rise through the ranks to the army's highest office, magister militum, by emperor Constans, despite being uneducated and unconnected.

He had held this command for a long period of time, and by 350 was considered an officer of both popularity and experience. In early 350, the commander of the famed Ioviani and Herculiani units, Magnus Magnentius, rose in rebellion and had Constans assassinated and himself crowned as emperor. He quickly asserted control of the western territories, but stopped at the border of Vetranio's province, Illyricum. Three months later, Vetranio is declared emperor by his soldiers. The exact nature of these and ensuing events, and the question of why Vetranio was declared emperor has puzzled recent historians.

Early historians, such as Edward Gibbon and Otto Seeck, following the account of ancient historian Philostorgius, proposed the idea that after the murder of Constans, Constantina, his sister and the daughter of Constantine the Great, asked the aged Vetranio to assume the purple, which he did on 1 March. She most likely thought Vetranio could protect her family and herself against the usurper, and merely hoped to secure his fidelity, though Edward Gibbon credits her notoriously unscrupulous ambition for the scheme, suggesting interested motives on her part. As a member of the imperial family and potentially an Augusta herself, Constantina could have potentially acted as the auctor of imperial authority and legitimately given Vetranio the imperial position. In any case, Constantius II was then embroiled in a dangerous struggle with Shapur II, the king of the Sasanian Empire. Constantina may have doubted her brother's abilities.

Recently, this story has been revised by taking a more comprehensive look at a broader range of source material. John Drinkwater points out that because Magnentius extended his territorial control only as far as northern Italy and ceased expanding well before Vetranio was declared emperor, Vetranio’s rebellion was not done out of an immediate pressure to keep Magnentius out of Illyricum to secure it for Constantina or Constantius, and was therefore as much a rebellion against Constantius as it was against Magnentius. Drinkwater still argues that ultimately Vetranio remained loyal to the Constantinian dynasty, and this idea is shared by Alan Dearn, who looked at the numismatic (coin) evidence, and Andrastos Omissi. However, these loyalist theories are ultimately unable to adequately explain why Vetranio needed to be usurp imperial authority at all. Although he was not actually a magister militum under Constantius, having been promoted by Constans, it still would have been a much safer course of action for himself, and everyone else involved in the undertaking, if he simply remained a magister militum and declared his loyalty for Constantius. Such was the choice made in 361 by Lucillianus, the magister militum in Sirmium, potentially the exact same city in which Vetranio was raised to the purple. Facing down the approaching armies of the usurper Julian, Lucillianus remained a loyal general of Constantius. No counter-rebellion was necessary. Thus there is no good explanation for why Vetranio usurped imperial power in 350, other than his own ambition.

Emperor
Vetranio accepted the purple, and coins were minted in his name, showing the title of Augustus (full emperor), rather than Caesar, and the coins indicated that he expected to rule for five years, and hoped for ten. Understandings for the sequence of events, and the real motivations behind them, again hinge on whether one believes Vetranio was a Constantinian loyalist or a self-interested usurper. It is clear that Vetranio liaised with Constantius and received some sort of approval and support from him - according to Philostorgius, Constantius sent Vetranio a diadem, and Julian reports that Constantius supported him with money and troops - but then Vetranio also developed a relationship with Magnentius. The older understanding of this development is that Vetranio feared an attack from Magnentius, but as described above, Magnentius intentionally stopped short of Illyricum and made no additional threats to the area, so Vetranio can hardly have felt in danger.

Both Vetranio and Magnentius put images of Constantius on their coins and not each other, indicating that they hoped to gain his respect more than the other's. Eventually, Constantius left from the eastern frontier with a large army, and met with ambassadors from both rebel emperors at Heraclea in Thrace. They offered him the senior title in the Empire, and Magnentius proposed to wed his daughter to Constantius, himself to marry Constantia the emperor's sister. But they required that the emperor ratify their claims to the western provinces. Constantius, supposedly inspired by his father Constantine in a nocturnal vision, indignantly declined the offer.

The first rebel Constantius needed to deal with was Vetranio. He had occupied the Succi Pass, an important and defensible thoroughfare on the Via Militaris, close to Serdica. This was the main road on which Constantius must proceed westwards. It is not exactly clear what occurred at the Succi Pass - those who believe Vetranio was loyal to Constantius argue that Vetranio had already organised his eventual surrender to Constantius, but some primary sources indicate that Vetranio was betrayed by his Praetorian Prefect, Vulcacius Rufinus, who was the envoy who met Constantius at Heraclea, as well as by the officer Gomoarius, who was perhaps in charge of Vetranio's defences at Succi.

If this was not his own secret plan, Vetranio must have now realised his position was untenable. He had lost his best defensive position, most likely a large portion of his army along with its senior officers, and was facing a much larger and more experienced eastern field army. Vetranio's and Constantius' forces met at Serdica under a truce, and then they proceeded to Naissus together. If it had not been negotiated already, there can be no doubt that on this march the emperor and rebel reconciled, while Constantius' agents distributed bribes amongst the armies to ensure their loyalty to Constantius. Then, at Naissus, on 25 December 350, in a contrived scene the two emperors mounted a tribunal to address the assembled legions; Constantius succeeded, by means of a strong speech, in which he invoked the glories of the house of Constantine I, to have the Illyrian legions acclaim him sole emperor. Most likely in a pre-planned show, Vetranio threw himself on the ground and begged Constantius' clemency. The emperor gently raised the aged general by the hand, honoring him with the name of father, and gave him instant pardon.

Later life and death
Later he was dismissed in peace. Though dismissed from his command, he was allowed to live the remainder of his years as a private citizen on a state pension in Prusa ad Olympum, Bithynia. He lived a further six years, dying in simple happiness. He is said to have recommended to Constantius as his friend, during his happy retirement in Brusa, that peace could only be obtained in a private station.