Pelagius, elected Pope as Justinian's candidate, is consecrated in 556, replacing Vigilius, who had died in the previous year.

While before his ordination he had opposed Justinian's efforts to condemn the "Three Chapters" in order to reconcile theological factions in the Church, afterwards Pelagius had adopted Justinian's position.

This has damaged the papacy's reputation in northern Italy, Gaul, and elsewhere in Western Europe, and his successors over the next fifty years will spend much effort undoing the damage.

The Empire had turned its attention from Rome and the West, following the death of Emperor Justinian I in 565, to pressing problems in the Balkans, from the Avars, the Persians and the Arabs.

The invasion of the Lombards begins in 568.

Much of northern Italy is overrun, as well as the central spine of the peninsula, making a shambles of the imperial administration.

Further, their warriors threaten the survival of Rome herself, subjecting the Eternal City to repeated sieges.

Lastly, their entrance reintroduces the newly extinguished Arian belief, which threatens the predominance of Roman Catholicism.

Pope John III dies on July 7, 574, during the stormy times of the Lombard invasion, for which reason practically all the records of his reign have been destroyed.