In ad 476 the last independent Roman emperor of the West, Romulus Augustulus, was dethroned by the invading Germanic chieftain Odoacer, who thereupon succeeded to the throne. In 488 Theodoric, king of the Ostrogoths, invaded Italy and, after defeating and slaying Odoacer, became the sole ruler in Italy. Theodoric ruled until his death in 526. In 535 Justinian I, emperor of the Eastern Roman Empire (see Byzantine Empire), dispatched the great general Belisarius to expel the Germanic invaders from Italy. A fierce war ensued, ending in 553 with the death of Teias, the last of the Gothic kings. The Byzantine rule was of short duration, however, for in 572 Italy was invaded by the Lombards, another Germanic tribe. Alboin, their king, made Pavia the capital of his realm, and from that city he launched a series of campaigns that eventually deprived the Byzantine power in Italy of everything except the southern portion of the province and the exarchate of Ravenna in the north. The country’s most important religious leaders of the time were the archbishops of Ravenna.

Under the military emperors of the late 3rd century, most notably Diocletian (284–305), the political structures of the Roman Empire were put onto a new footing. The army was restructured after the disasters of the previous 50 years; the civil bureaucracy and the ceremonial rituals of imperial rule were considerably developed; and, above all, the tax system was reorganized and enlarged. The fiscal weight of the late Roman Empire was heavy, given the resources of the period: its major support, the land tax, collected by local city governments, took at the minimum one-fifth, and probably one-third, of the agricultural produce. On the other hand, the administration and the army that the tax system paid for reestablished a measure of stability for the empire in the 4th century. Central government was not always stable; there were several periods of civil war in the 4th century, notably in the decade after Diocletian's retirement and in the years around 390. But succession disputes had been a normal part of imperial politics since the Julio-Claudians in the 1st century AD; in general, self-confidence in the 4th-century empire was fairly high. Aggressive emperors such as Valentinian I (364–375) could not have been able to imagine that within a century nearly all of the Western Empire was to be under “barbarian” rule

Under the military emperors of the late 3rd century, most notably Diocletian (284–305), the political structures of the Roman Empire were put onto a new footing. The army was restructured after the disasters of the previous 50 years; the civil bureaucracy and the ceremonial rituals of imperial rule were considerably developed; and, above all, the tax system was reorganized and enlarged. The fiscal weight of the late Roman Empire was heavy, given the resources of the period: its major support, the land tax, collected by local city governments, took at the minimum one-fifth, and probably one-third, of the agricultural produce. On the other hand, the administration and the army that the tax system paid for reestablished a measure of stability for the empire in the 4th century. Central government was not always stable; there were several periods of civil war in the 4th century, notably in the decade after Diocletian's retirement and in the years around 390. But succession disputes had been a normal part of imperial politics since the Julio-Claudians in the 1st century AD; in general, self-confidence in the 4th-century empire was fairly high. Aggressive emperors such as Valentinian I (364–375) could not have been able to imagine that within a century nearly all of the Western Empire was to be under “barbarian” rule.