The Byzantine Empire was the continuation of the Roman Empire in its eastern, Greek speaking provinces after the fall of the western half in the fifth century CE, governed from its capital at Constantinople until the city fell to the Ottomans in 1453. Byzantine emperors continued to call themselves Roman, and the empire preserved Roman law, in the form of Justinian's sixth century legal code, alongside Greek language and culture and, from its earliest centuries, Orthodox Christianity as the state religion. At its height under Justinian in the sixth century it briefly reconquered much of the western Mediterranean, and for centuries afterward it remained one of the wealthiest and most sophisticated states in the world, a major center of trade, learning and religious art whose preservation of ancient Greek texts later helped fuel the Renaissance in western Europe. Repeated wars with Persia, the Arab caliphates, the Seljuk Turks, western Crusaders, who sacked Constantinople itself in 1204, and finally the Ottomans steadily reduced its territory until only the city of Constantinople and its immediate surroundings remained by the fifteenth century.