The terms Byzantine Empire (a historiographical term used since the 19th century) and Eastern Roman Empire are expressions used to describe the Roman Empire of the Middle Ages, centered on its capital of Constantinople, referred to by its inhabitants simply as the Roman Empire (in Greek Βασιλεία Ῥωμαίων) or Romania (Ῥωμανία), its emperors continuing the unbroken succession of Roman emperors, preserving Greco-Roman legal and cultural traditions; to the Islamic world it was known primarily as روم‎ (Rûm, "land of the Romans"). Due to the dominance of Medieval Greek language, culture and population,[3] it was known to many of its western European contemporaries as Empire of the Greeks. As an outgrowth of the eastern portion of Empire founded in Rome, the Byzantine Empire's evolution into a separate culture from the West can be seen as a process beginning with Emperor Constantine's transferring the capital from Nicomedia in Anatolia to Byzantium on the Bosphorus (then renamed Nova Roma, and later Constantinople). By the 7th century under the reign of Emperor Heraclius, whose reforms changed the nature of the Empire's military and recognized Greek as the Empire's language, the Empire had taken on a distinct new character. During its existence the Empire suffered numerous setbacks and losses of territory yet it remained one of the most powerful economic, cultural and military forces in Europe. The empire's influence also spread into North Africa and the near East for much of the Middle Ages. After a final recovery under the Komnenian dynasty in the 12th century the Empire slipped into a long decline culminating in the capture of Constantinople and the remaining Roman/Greek territories by the Ottoman Turks in the 15th century. During her thousand-year reign the Empire, a bastion of Christianity and one of the prime trade centers in the world, helped to shield Western Europe from early Muslim expansion, provided a stable gold currency for the Mediterranean region, influenced the laws, political systems, and customs of much of Europe and the Middle East, and preserved much of the literary works and scientific knowledge of ancient Greece, Rome, and many other cultures.