For more than five centuries after Justinian, the Roman Empire in the East was engaged in a long struggle with the foes—Persians, Arabs, and Seljuk Turks—which successively attacked its dominions. By its stubborn resistance of the advance of the invaders the old empire protected the young states of Europe from attack, until they grew strong enough to meet and repulse the hordes of Asia. This service to civilization was not less important than that which had been performed by Greece and Rome in their contests with the Persians and the Carthaginians.