CONSTANTINE III (Flavius Claudius Constantinus)
On 31st December in 406 several tribes of Barbarian invaders, including the Vandals, the Burgundians, the Alans and the Sueves, crossed the frozen river Rhine, perhaps near Mainz, and overran the Roman defensive works in a successful invasion of the Western Roman Empire.
At the time of this invasion, the provinces of Britain were in revolt. In 406, the troops hailed their commander, known only as Marcus, as emperor. He was assassinated shortly after, but another officer called Gratianus was acclaimed, only to be murdered 4 months later at the start of 407. Finally, fearful of a Germanic invasion, the Roman military in Britain chose as their leader Flavius Claudius Constantinus, a common soldier (probably a centurion), but one of some ability.
Constantine, instead of acting to protect Britain, crossed the English Channel to the continent at Bononia and took along with him all of the mobile troops left in Britain, leaving it virtually undefended. Constantine's two generals Iustinianus and the Frank Nebiogastes, leading the vanguard of his forces, were defeated by Sarus, and Stilicho's lieutenant, with Nebiogastes being first trapped in, then killed outside, Valence. However, Constantine sent another army headed by Edobichus and Gerontius, and Sarus was forced to retreat into Italy, needing to buy his passage through the Alpine passes from the brigand Bagaudae, who controlled them. Constantine secured the Rhine frontier, and garrisoned the passes that led from Gaul into Italy. By May 408 he had made Arelate (Arles) his capital, where he appointed Apollinaris, the grandfather of Sidonius Apollinaris, as prefect.
In the summer of 408, the Roman forces in Italy assembled to counterattack. Constantine, fearful that several cousins of the Emperor Honorius in Hispania, which was a stronghold of the House of Theodosius and loyal to the ineffectual emperor, would organize an attack from there while troops under Sarus and Stilicho attacked him from Italy, he struck first at Hispania. He summoned his eldest son Constans from the monastery where he was living, elevated him to Caesar, or co-emperor, and sent him with the general Gerontius towards Hispania. The cousins of Honorius were defeated. Two, Didymus and Theodosiolus, were captured, while two others, Lagodius and Verianus, managed to escape to Constantinople.
Constans left his wife and household at Caesaraugustus (Saragossa) under the care of Gerontius to return to report to Arelate. Meanwhile the loyalist Roman army mutinied at Ticinum (Pavia) on 13th August, which was followed by the execution of the patrician Stilicho on 22nd August. As a result of this, the general, Sarus, abandoned the western army and followed by his men. This left the Emperor Honorius in Ravenna without any significant military power, and facing a Gothic army under Alaric roaming unchecked in Etruria. So, when Constantine's envoys arrived to talk at Ravenna, the fearful Honorius eagerly recognized Constantine as co-emperor, and the two were joint consuls for the year 409.
But by September, the tribes that had overrun the Rhine defences, and had spent the intervening two years and eight months burning and plundering their way through Gaul, had reached the Pyrenees, where they broke through Constantine's garrisons and entered Hispania. While Constantine prepared to send his son Constans back to deal with this crisis, word came that his general Gerontius had rebelled, raising his relative, Maximus, as co-emperor. In 410 Gerontius advanced with the support of his barbarian allies.
Meanwhile, Saxon pirates raided Britain, which Constantine had left defenceless. Upset that Constantine had neglected them in his efforts to establish his own empire, the Roman inhabitants of Britain and Armorica rebelled against Constantine's authority and expelled his officials.
In response to all this, Constantine marched on Italy with the remaining troops left to him, encouraged by the entreaties of one Allobich who wanted to replace Honorius with a more capable ruler. But this invasion ended in defeat, with Allobich losing his life and Constantine forced to retreat into Gaul in the late spring of 410.
In 411 Constantine's forces facing the rebel Gerontius were defeated at Vienna (Vienne), where his son Constans was captured and executed. Constantine's Praetorian prefect Decimus Rusticus, who had replaced Apollinaris a year earlier, abandoned Constantine, to be caught up in the new rebellion of Jovinus in the Rhineland. Gerontius trapped Constantine inside Arles and besieged him.
At the same time a new general was found to support Honorius, by the name of Constantius - the future Constantius III. He arrived at Arelate, put Gerontius to flight and then took over the siege of Constantine in Arelate. Constantine held out, hoping for the return of his general Edobichus who was raising troops in northern Gaul amongst the Franks, but on his return Edobichus was defeated by a simple stratagem.
When Constantine's last troops guarding the Rhine abandoned him to support Jovinus, he was forced to surrender. Before his surrender, Constantine III took holy orders and became a priest. Despite this and the promise of safe passage, Constantius had Constantine and his youngest son, Julianus, beheaded on their way to Ravenna in either August or September 411.
Although Gerontius committed suicide in Hispania, and Athaulf the Visigoth later suppressed the revolt of Jovinus, Roman rule never returned to Britain after the death of Constantine III: as the historian Procopius later explained, "from that time onwards it remained under [the rule] of tyrants."
Constantine III is also known as Constantine II of Britain. He was remembered as a King of the Britons in the Welsh chronicles and Geoffrey of Monmouth's highly popular and legendary Historia Regum Britanniae, where he comes to power following Gracianus Municeps' reign, which had ended with his assassination. He also found his way into some of the Arthurian stories.