Istanbul (Turkish: İstanbul), historically known as Constantinople and Byzantium, is the largest city in Turkey and amongst the largest of cities in the world, with a population nearing 13 million. For the most part, Istanbul is located in the European part of Turkey, Thrace, but extends into parts of Asia-Minor. While Ankara is the formal capital of Turkey, Istanbul is largely considered the cultural and financial capital of the nation. Since the Fourth century, Istanbul has been a major city, known by names such as Byzantium and Constantinople.
As Constantinople the city served as the capital of four major empires: The Roman Empire (330-395), the Byzantine Empire as the surviving offshoot of the old Roman Empire (395-1204 and 1261-1453), the Latin Empire (1204-1261), and the Ottoman Empire (1453-1922). Formerly the city of Byzantium, Constantine renamed it as Constantinople in A.D. 330. It was designed to be the Rome of the East (Nova Roma, or "New Rome"). It was conquered by the Ottoman Sultan Mahmud II in 1453 after being defended by Constantine XI, the last of the Byzantine Emperors, and his small army. It served as the capital of the Ottoman Empire until the Empire was broken apart by the First World War. History as a Christian Metropolis The city was founded by Constantine in A.D. 330. Although originally he named it Nova Roma, which was Latin for "new Rome," the mostly Greek residents he settled in the city called it Constantinopolis, and in English this is Constantinople. He made it the capital of the Roman Empire, but for fifty years most emperors spent most of their reigns not in Constantine's palace but fighting against either the Persians or the Germans. Emperor Theodosius was the first potentate to spend most of his reign in the city. When he died in 395, the empire split into western and eastern halves. In 527 Justinian became emperor and issued a collection of all laws ever published by the Roman emperors, from Augustus to Theodosius. When a fire destroyed most of Constantine's buildings, Justinian rebuilt in a magnificent half-Greek, half-Oriental, and half-Roman style. His most famous building was the Hagia Sophia, built in 537 in Asian style. During the early seventh century, the city was threatened by the Persians, but the emperor Heraclius raised a large and well-equipped army which defeated them and retook Syria, Palestine, and Egypt, which the Persians had seized. But then the Arabs, now followers of Islam, seized Syria, Egypt, Palestine, and North Africa. Meanwhile, lands in northern Italy and southern Spain taken by Justinian were lost to Germanic kings.
In 1071, the Seljuk Turks, who had converted to Islam, took all of Asia Minor and threatened to sail across the Bosporus and seize Constantinople. Twenty-four years later, Emperor Alexius IV appealed to Pope Urban II, who by the power of his speech convinced the French, the Germans, and the English to embark on a Crusade or holy war to protect Byzantium and seize Jerusalem from the Muslims. Both succeeded, but in 1204 French knights headed to Egypt sacked Constantinople, installed a Western emperor, and tried to make Byzantium Catholic and Latin-speaking. Yet in 1261 the exile Michael Palelogoi seized the city and became Emperor Michael VIII. He restored much of the city's wealth and fortifications, but wasted troops on seizing Asia Minor.