Constans II (died 411) was the son of Western Roman emperor Constantine III, and served as his co-emperor from 409 to 411.

Later in 409 Gerontius rebelled, proclaimed his client Maximus emperor and incited barbarian groups in Gaul to rise up.

[1] Honorius was underage and the leading general Stilicho became hugely influential and the de facto commander-in-chief of the Roman armies in the west.

[2] Both the Eastern and Western Empires were suffering from incursions of large groups from Germanic tribes, whom the Romans referred to generically as "barbarians".

[13] They next chose as their leader a man named after the famed emperor of the early fourth century, Constantine the Great, who had himself risen to power through a military coup in Britain.

Flavius Claudius Constantinus[14][15] was a common soldier[note 2] and early in 407, possibly February, his fellows acclaimed him as emperor.

[19] However, such revolts were usually short-lived; Constantine was uncommon in both establishing a lasting power base and in successfully exporting his rebellion to the mainland.

[20] Constantine moved quickly: he appointed generals in Gaul and crossed the Channel at Bononia (modern Boulogne).

Constantine also negotiated agreements with the Germanic groupings of the Franks, Alamanni and the Burgundians, thus securing the line of the Rhine.

[26][27] Another army, led by Gerontius and Edobichus and largely made up of freshly recruited Franks and Alamanni, arrived to relieve Valence after a week of siege.

[33] By May 408 Constantine had captured Arles and made it his capital,[34] taking over the existing imperial administration and officials, and appointing Apollinaris as chief minister (with the title of praetorian prefect).

[note 4][38] Constantine commenced minting large quantities of good quality coins at Arles and made a show of being an equal of both the Western and Eastern Emperors.

[28][39] Hispania was a stronghold of the House of Theodosius,[34] but on Constantine's initial landing on the continent, Honorius's partisans had been either unwilling or militarily unable to oppose his assumption of control.

When Sarus withdrew to Italy the knowledge of the large new army assembling at Ticinum with the intention of shortly engaging Constantine encouraged them to persist and even to attempt to seal the Pyrenean passes.

With Hispania back under Constantine's control Constans left his new wife at Saragossa and returned to Arles to report to his father.

The Roman establishment, led by the senior bureaucrat Olympius, worked to oppose Stilicho by spreading rumours that he wished to travel east to depose Theodosius and set his own son, Eucherius, on the throne.

[43] The native parts of the Army of Italy, encouraged by Olympius,[note 5] started slaughtering Goths: the wives and children of their fellow soldiers who were living in Italian cities, sometimes overtly as hostages for their husbands and fathers' good behaviour, were easy targets.

Gerontius was concerned that he would not be able to withstand the military force Constans could bring to bear and so attempted to incite the barbarians who had entered Gaul late in 406 against Constantine.

Concentrating on the threat from Constans, Gerontius weakened his garrisons in the Pyrenean passes and in autumn 409 much of the barbarian force entered Hispania.

[51][52] Eventually Gerontius was able to reach a modus operandi with some of these groups whereby they supplied him with military forces, which enabled him to take the offensive against Constans.

[55] In 411 Honorius appointed a new general, Flavius Constantius, who took the Army of Italy over the Alps and arrived at Arles while Gerontius was outside the city.

[58] Constantine, his hopes fading after the troops guarding the Rhine abandoned him to support yet another claimant to the imperial throne, the Gallic Roman Jovinus, surrendered to Constantius along with his surviving son Julian.

Gaul was pacified, the barbarians in Hispania were in large part subdued, the Visigoths were settled on land in Aquitaine as Roman allies.