The foundation upon which the Eastern Roman Empire will rest for nearly a century is laid by Justinian, whose administrative reforms greatly advance the unification of the diverse peoples of the empire in a Hellenic context.

He wages almost constant warfare between 535 and 554 in the west.

Drawing his professional forces mostly from the Balkans, he greatly expands the empire's territory by conquering the southern Levant, northern Africa, and Italy, in an effort to recreate the domain of the old Roman Empire.

Justinian has driven the invaders from the Roman empire, but imperial defenses will prove inadequate to maintain this gain, and his institutional reforms will prove far more lasting than his military conquests.