The Donatists, who establish their own communities, appoint bishops, and convene church councils, vigorously resist opposition from both the traditional church and the Roman state.

The rigoristic Donatist teachings proclaim that only the sinless can belong to the true church, that sacraments conferred by sinful ministers are invalid, and that only baptism conferred by a Donatist is valid.

Because the Donatists had denied the representative character of two earlier synods, at Rome and in Africa, at which they had been condemned, Constantine convenes the first representative meeting of Christian bishops in the Western Roman Empire at Arles in southern Gaul in August 314.

Attended by representatives of forty-three bishoprics, the Donatists are again condemned, but they reject the decisions reached by the council and again appeal to Constantine to review their case.

Constantine, joined by Roman legions from Spain, has by May 408 made Arles his capital, where he appoints Apollinaris, the grandfather of Sidonius Apollinaris, as prefect.

In the summer of 408, as the Roman forces in Italy assemble to counterattack, Constantine has other plans.

Hispania is a stronghold of the House of Theodosius and loyal to the ineffectual emperor.

Fearful that several cousins of the emperor Honorius will organize an attack from that direction while troops under Sarus and Stilicho attack him from Italy in a pincer maneuver, Constantine strikes first at Hispania.

He summons his eldest son Constans from the monastery where he is dwelling, elevates him to caesar, or junior emperor, and sends him with the general Gerontius towards Hispania.

The cousins of Honorius are defeated without much difficulty and two—Didymus and Theodosiolus—are captured, while two others—Lagodius and Verianus—manage to escape to safety in Constantinople.

Constans executes the two captives and leaves his wife and household at Saragossa under the care of Gerontius to return to report to Arles.

Constantine has threatened to invade Italy but in 409 loses control of Britain, and in late summer writes to Honorius, asking forgiveness for having seized power and promising help against Alaric in Italy.

Honorius recognizes him as joint emperor, sending an imperial robe to Constantine and possibly granting him the consulate.

The tribes that had overrun the Rhine defenses in 406 and spent the intervening years burning and plundering their way through Gaul, have reached the Pyrenees, where, led by king Gunderic, they break through Constantine's garrisons and enter Hispania in September 409.

While Constantine prepares to send his son Constans back to deal with this crisis, word comes that his general Gerontius has rebelled, raising his own man as co-emperor.

Constantine's praetorian prefect Decimus Rusticus, who had replaced Apollinaris a year earlier, abandons Constantine, to be caught up in the new rebellion of Jovinus in the Rhineland.

Gerontius traps Constantine inside Arles and besieges him.

Ataulf’s first act following his unanimous election to the Visigothic supreme command had been to halt Alaric's southward expansion of the Goths in Italy.

He has led the Goths into Gaul at the instigation of Honorius, who has promised to recognize a Visigothic Kingdom if he defeats the several usurpers who threaten the Roman Empire.

At the same time, a new general has been found to support Honorius.

Constantius, Honorius' Moesian-born magister militum (master of the soldiers), enters Gaul in 411 and, after defeating Gerontius, in turn besieges Constantine in Arles.

Constantine holds out, hoping for the return of his general Edobichus, who is raising troops in northern Gaul among the Franks, but on his return, Edobichus is defeated by a simple stratagem.

Constantine's last slender hope fades when his last troops guarding the Rhine abandon him to support Jovinus.

He takes refuge in a church and is ordained before surrendering to Constantius.

Majorian, a young, capable general in his late thirties, decides the first step towards consolidating the empire is to confront the Visigoths in Septimania.

Traveling with his generals Aegidius and Nepotianus, Majorian encounters the Visigothic king and his army at Arelate, at the mouth of the Rhodanus river (Rhone).

The ensuing battle is an overwhelming Gothic defeat.

Theodoric II is forced to flee Arelate, abandon Septimania, and conclude a hasty peace treaty.

The treaty returns all Visigothic territory in Hispania to the Romans, and the Visigoths are reduced to federate status.

The battle allows Majorian to campaign deeper in Gaul against the Burgundian Kingdom, and later in Hispania against the Suebic Kingdom.