Flavius Placidius Valentinianus (born 419, died 455), known in English as Valentinian III, was Western Roman Emperor (425-455, Rome's longest reigning emperor). Theodosius nominated Valentinian Caesar of the west (October 23, 424), and bethrothed him to his own daughter Licinia Eudoxia (Valentinian would marry her in 437). In 425, after Emperor Joannes had been defeated in war, Valentinian was installed Western Emperor in Rome, on October 23, at the age of six.
Given his minority, the Valentinian ruled under the control first of his mother, and then, after 433, of the Magister militum Flavius Aëtius. Valentinian's reign is marked by the dismemberment of the Western Empire; the conquest of the province of Africa by the Vandals in 439; the final abandonment of Britain in 446; the loss of great portions of Spain and Gaul, in which the barbarians had established themselves; and the ravaging of Sicily and of the western coasts of the Mediterranean Sea by the fleets of Genseric.
As an off-set against these calamities, there was the great victory of General Aëtius (one of the two "Last of the Great Romans") over Attila the Hun in 451 near Chalons, and his successful campaigns against the Visigoths in southern Gaul (426, 429, 436), and against various invaders on the Rhine and Danube (428-431).
The burden of taxation became more and more intolerable as the power of Rome decreased, and the loyalty of its remaining provinces was seriously impaired in consequence. Ravenna was Valentinian's usual residence; but he fled to Rome on the approach of Attila, who, after ravaging the north of Italy, died in the following year (453).
Although in 453 Aëtius had been able to betroth his son Gaudentius to Valentinian's daughter Placidia, Valentinian felt intimidated by Aëtius, who had once supported Joannes against him and whom Valentinian believed wanted to place his son upon the imperial throne. The Roman senator Petronius Maximus and the chamberlain Heraclius were therefore able to enlist Valentinian in a plot to assassinate Aëtius. On September 21, 454, when at court in Ravenna delivering a financial account, Aëtius was slain by Valentinian's own hand. Edward Gibbon credits Sidonius Apollinaris with the famous observation, "I am ignorant, sir, of your motives or provocations; I only know that you have acted like a man who has cut off his right hand with his left" (Decline and Fall of the Roman Empire, ch. 35).
Maximus expected to be made patrician in place of Aëtius, but was blocked by Heraclius. Seeking revenge, Maximus arranged with two Hun friends of Aëtius, Optila and Thraustila, to assassinate both Valentinian III and Heraclius. On March 16, 455, Optila stabbed the emperor in the temple as he dismounted in the Campus Martius and prepared for a session of archery practice. As the stunned emperor turned to see who had struck him, Optila finished him off with another thrust of his blade. Meanwhile, Thraustila stepped forward and killed Heraclius. Most of the soldiers standing close by had been faithful followers of Aëtius and none lifted a hand to save the emperor. (from Wikipedia articles)
http://en.wikipedia.org/wiki/Valentinian_III
http://www.livius.org/va-vh/valentinian ... n_iii.html
http://www.roman-emperors.org/valenIII.htm
http://www.roman-empire.net/collapse/va ... n-III.html
http://rubens.anu.edu.au/raid5/italy200 ... /colossus/ (The "Colossus of Barletta" thought to be a Western Roman emperor between Valentinian I [364-375] and Marcian [450-7], inclusive)
Coins of Valentinian III:
Military image (NumisWiki).
Other coins of Valentinian III:
http://www.wildwinds.com/coins/ric/vale ... III/i.html
Valentinian III (seated) and Aëtius, from the TV mini-series "Attila" (2001)