The Roman Empire in the East, though threatened by enemies from without and weakened by civil conflicts from within, endured for more than a thousand years. Until the middle of the fifteenth century it preserved the name, the civilization, and some part of the dominions, of ancient Rome.

The long life of the Roman Empire in the East is one of the marvels of history. Its great and constant vitality appears the more remarkable, when one considers that it had no easily defensible frontiers, contained many different races with little in common, and on all sides faced hostile states.