Barbarian invasions and Byzantine Italy, c. 400–c. 600

Theodosius had commanded the army himself, but his successors in the fifth century allowed military authority to slip from their hands. Thus Honorius (395–423) appointed a man who was by race a Vandal, Stilicho, as commander, or magister militum. Stilicho drove the Visigoths, under Alaric, out of Greece, and continued his victories into Northern and Central Italy, but in an attempt to regain control of the armies, Honorius had Stilicho murdered in 408. The immediate future for Italy lay with the Visigoths, the westward branch of the Goths, a Teutonic tribe which had probably been dislodged from Southern Russia by nomadic peoples in the 370s. The Visigoths thus reached Italy at the beginning of the fifth century, under their leader, Alaric.

Alaric I, like Stilicho, was in a sense a product of the Empire. He had been appointed by Theodosius as leader of initially loyal Gothic auxiliaries. But in 395 he had invaded Northern Greece, and in 400 or 401 made an unsuccessful attack on Northern Italy. In 401 he besieged Milan, and in 410 sacked Rome. In spite of the waves of horror which swept the Empire at the news of the sacking of Rome, the city recovered in some twenty years, with renewed building activity. Meanwhile other barbarians were approaching Italy from another direction. The Vandals arrived in Africa in 429, having crossed Gaul and Spain with remarkable speed.