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.
In 425, the court at Ravenna negotiated with the Huns who had accompanied Aetius to Italy in support of Joannes. The Huns agreed to leave Italy, and to evacuate the province of Pannonia Valeria, which was returned to the empire. This allowed Felix and the imperial government to restructure the defences along the Danubian provinces in 427 and 428. In addition, there were significant victories over the Visigoths in Gaul in 426/7 and 430 and the Franks along the Rhine in 428 and 432.
Nevertheless, there were significant problems that threatened the viability of the Roman state in the west. The Visigoths were a constant presence in south-eastern Gaul and could not be dislodged. The Vandals in Hispania continued their incursions, and, in 429, commenced an invasion of Mauretania Tingitana. The loss of these territories seriously impacted the state's ability to function. The burden of taxation became more and more intolerable as Rome's power decreased, and the loyalty of its remaining provinces was impaired in consequence.
The initial period of Valentinian's reign was further troubled by a power struggle among the three principal military leaders of the west – Felix, the senior magister militum praesentalis, Bonifatius, the magister militum per Africam, and Aetius, the magister militum per Gallias. In 427, Felix accused Bonifatius of treason and demanded that he return to Italy. Bonifatius refused and defeated an army sent by Felix to capture him. Weakened, Felix was unable to resist Aetius who, with the support of Galla Placidia, replaced him as magister militum praesentalis in 429, before having him killed in 430.
Bonifatius, in the meantime, had been unable to defeat Sigisvultus, whom Galla Placidia had sent to deal with the rebel. Bonifatius, therefore, entered into an agreement with the Vandals to come to his aid and, in return, they would divide the African provinces between themselves. Concerned by this turn of events and determined to hold onto the African provinces at all costs, the court at Ravenna sought reconciliation with Bonifatius, who agreed in 430 to affirm his allegiance to Valentinian III and stop the Vandal king Gaiseric.
In 431, Bonifatius was crushed and fled to Italy, abandoning western North Africa. The imperial court, and especially Galla Placidia, worried about the power being wielded by Aetius, stripped him of his command and gave it to Bonifatius. In the civil war that followed, Bonifatius defeated Aetius at the Battle of Ravenna, but died of his wounds. Aetius fled to the Huns and, with their help, was able to persuade the court to reinstate him to his old position of magister militum praesentalis in 434. As a consequence, in 435, Valentinian was forced to conclude a peace with Gaiseric, whereby the Vandals kept all their possessions in North Africa in return for a payment of tribute to the empire, while the Huns were granted new territory in Pannonia Savia to occupy.
Galla Placidia's regency came to an end in 437 when Valentinian travelled to Constantinople to marry his fiancée, Licinia Eudoxia. On his return to Rome, he was nominally the emperor, but in truth the management of imperial policy in the west was in the hands of Aetius.
Ascendancy of Aetius (437–455)
From 436 to 439, Aetius was focused on the situation in Gaul. Serious Gothic defeats in 437 and 438 were undone by a Roman defeat in 439, which saw the status quo restored through a new truce. He also enjoyed initial success against the Franks and the Burgundians, as well as putting down a revolt by the Bagaudae by 437. In 438, peace was also achieved with the Suebi in Spain, the same year Valentinian's daughter, Eudocia, was born.
With Aetius occupied in Gaul, Valentinian was unable to do anything to prevent the Vandals completely overrunning the remaining western African provinces, culminating in the fall of Carthage on 19 October 439. This was a major blow because taxes and foodstuffs from these wealthy provinces supported Rome. By 440, Vandal fleets were ravaging Sicily and Aetius coordinated a joint response with the eastern court, with large numbers of Roman troops sent to defend the island from Gaiseric. Hunnic invasions forced the government to abandon this defense and transfer the troops to the Danube.