In the east a resurgent Byzantine Empire recaptured Crete and Cyprus from the Muslims and reconquered the Balkans. Constantinople was the largest and wealthiest city in Europe from the 9th to the 12th centuries, with a population of approximately 400,000. The Empire was weakened following the defeat at Manzikert and was weakened considerably by the sack of Constantinople in 1204, during the Fourth Crusade. Although it would recover Constantinople in 1261, Byzantium fell in 1453 when Constantinople was taken by the Ottoman Empire.