Valentinian III

Valentinian III (Latin: Placidus Valentinianus; 2 July 419 – 16 March 455) was Roman emperor in the West from 425 to 455. Starting in childhood, his reign over the Roman Empire was one of the longest, but was dominated by civil wars among powerful generals and the barbarian invasions. He was the youngest sole emperor in the Western Roman Empire (aged 6).

He was the son of Galla Placidia and Constantius III, and as the great-grandson of Valentinian I (r. 364–375) he was the last emperor of the Valentinianic dynasty. As a grandson of Theodosius I (r. 379–395), Valentinian was also a member of the Theodosian dynasty, to which his wife, Licinia Eudoxia, also belonged. A year before assuming the rank of augustus, Valentinian was given the imperial rank of caesar by his half-cousin and co-emperor Theodosius II (r. 402–450). The augusta Galla Placidia had great influence during her son's rule, as did the military commander Flavius Aetius, who defended the western empire against Germanic and Hunnic invasions. Attila the Hun repeatedly menaced Valentinian's domains, being repulsed by a coalition under Aetius's leadership at the Battle of the Catalaunian Plains and calling off a subsequent invasion after negotiations led by Pope Leo I.

The emperor later fell out with Aetius and killed him. Valentinian was assassinated in turn by Aetius's bodyguards, ending a reign marked by the ongoing collapse of the western empire.

Valentinian was born on 2 July 419 in Ravenna, the capital of the Western Roman Empire, as the only son of Galla Placidia and Constantius III, who briefly ruled as emperor in 421. His mother was the younger half-sister of the western emperor Honorius (r. 393–423), while his father was at the time a patrician and the power behind the throne.

Through his mother, Valentinian was a descendant both of Theodosius I, who was his maternal grandfather, and of Valentinian I, who was the father of his maternal grandmother. It was also through his mother's side of the family that he was the nephew of Honorius and first cousin to Theodosius II (the son of Honorius' brother Arcadius), who was eastern emperor for most of Valentinian's life. Valentinian had a full sister, Justa Grata Honoria. His mother had previously been married to Ataulf of the Visigoths, and had borne a son, Theodosius, in Barcelona in 414; but the child had died early in the following year, thus eliminating an opportunity for a Romano-Visigothic line.

In either 421 or 423, Valentinian was given the title of nobilissimus by Honorius, although this title was not initially recognized in the eastern court of Theodosius II. After the death of Constantius in 421, court intrigue forced Galla Placidia to flee from Honorius and move to Constantinople, where she, Valentinian and Honoria were taken in by Theodosius.

In 423, Emperor Honorius died, and his primicerius notariorum Joannes took power in Rome. To counter this threat to his power, Theodosius posthumously recognised Valentinian's father as augustus (emperor) and nominated the 5-year-old Valentinian caesar (heir-apparent) for the West in 23 October 424. Theodosius also betrothed his daughter Licinia Eudoxia to Valentinian, who would eventually marry her in 437 when he was 18. On 23 October 425, after Joannes had been defeated in a combined naval and land campaign, Helion, the eastern patricius et magister officiorum, installed Valentinian as augustus in Rome.

Given his minority, the new augustus ruled under the influence of his mother Galla Placidia, one of whose first acts was to install Felix as the magister utriusque militiae in the west. This period was marked by a vigorous imperial policy and an attempt to stabilize the western provinces as far as the stretched resources of the empire could manage.