Eugenius

Following the death of Valentinian II, Arbogast, who had probably been the cause of Valentinian II's murder or suicide, elevated Eugenius to the purple (22 August 392). Deferring to Eugenius offered Arbogast two strong advantages: first, Eugenius, a Roman, was more suitable than Arbogast, a Frank, as an emperor; furthermore, the Roman Senate would be more likely to support Eugenius.

After being installed as Emperor, Eugenius changed the imperial administrators. When Theodosius had left the western half of the empire to Valentinian II, he had put his own men in the highest civil offices, to keep a strong grasp on the whole empire. Eugenius replaced these administrators with others loyal to himself, coming from the senatorial class. Virius Nicomachus Flavianus the Elder became Praetorian Prefect of Italy, his son Nicomachus Flavianus the Younger received the title of Prefect of Rome, while the new praefectus annonae was Numerius Proiectus.

Though his actual beliefs are a matter of controversy among ancient and modern historians,[2][3] Eugenius was at least publicly a Christian, and therefore was reluctant to accept a program of imperial support to Polytheism. His men, however, convinced Eugenius to use public money to fund pagan projects, such as the rededication of the Temple of Venus and Rome and the restoration of the Altar of Victory within the Curia (removed by Emperor Gratian). This religious policy created tension with pro-Christian figures, such as Emperor Theodosius and the powerful and influential Bishop Ambrose, who left his see in Milan when the imperial court of Eugenius arrived.

Eugenius was also successful in the military field, notably in the renovation of old alliances with Alamanni and Franks. Arbogast, who was a Frank and had also Alamanni and Frankish soldiers in his ranks, marched to the Rhine frontier, where he impressed and pacified the Germanic tribes by parading his army in front of them.

After his election as emperor, Eugenius sent ambassadors to Theodosius's court, asking for recognition of his election. Theodosius received them, but started to gather troops to defeat Eugenius. Theodosius also promoted his eight-year-old son Honorius to the rank of "Augustus" of the West in January 393.

Theodosius then moved from Constantinople with his army, and met Eugenius and Arbogast in the Battle of the Frigidus (Vipava Valley, Slovenia) on 6 September 394. The bloody battle lasted two days, and was marked by unusual astronomical and meteorological events, but in the end Theodosius won. Arbogast immediately committed suicide after the defeat, while Eugenius was held for execution as a criminal, his head afterward being displayed in Theodosius' camp.