So in 411 Constantius, the magister militum (master of military) of the western emperor, Flavius Augustus Honorius, with Gothic auxiliaries under Ulfilas, crushed the Gallic rebellion with a siege of Arles.
Taking the advice of Priscus Attalus—the former emperor whom Alaric had set up at Rome in opposition to Honorius at Ravenna, and who had remained with the Visigoths after he'd been deposed—Athaulf led his followers out of Italy.
Athaulf then turned Sebastianus over for execution to Honorius' Gallic praetorian prefect (provincial governor), Claudius Postumus Dardanus.
The heads of Sebastianus and Jovinus arrived at Honorius' court in Ravenna in late August, to be sent forward for displaying among other usurpers on the walls of Carthage.
Athaulf, in turn, refused to release Galla Placidia and his army resumed their hostilities against the Romans, taking the cities of Narbonne, Tolosa and Burdígala (present-day Bordeaux).
In Hispania, Athaulf imprudently accepted into his service one of the late Sarus' followers, unaware that the man harbored a secret desire to avenge the death of his beloved patron.
The main sources for the career of Athaulf are Paulus Orosius, the chronicles of the Gallaecian bishop Hydatius, and those of Augustine's disciple, Prosper of Aquitaine.
The authenticity of Athaulf's declaration at Narbonne, as Orosius reported it in a rhetorical history that was explicitly written "against pagans" (it was completed in 417/18) has been doubted.