City, now Istanbul, on the European side of the Bosporus where it enters the Sea of Marmara dividing Europe from Asia, on both sides of the Golden Horn, an inlet of the Bosporus. Constantinople was the capital of the powerful Byzantine Empire and the largest and finest city in Europe, of the highest cultural and commercial importance. The city was founded in 667 b.c. by Greeks from Megara, and as Byzantium it grew in importance by reason of its location on the Bosporus, which also connects with the Black Sea. It changed hands several times during the Peloponnesian Wars of 431 to 404 b.c. Although Rome held the Bosporus area from at least 74 b.c., the city itself was captured in a.d. 196 by Septimius Severus of the Roman Empire. Constantine I, who became emperor in 324, moved his capital here in 330, rebuilt it as Constantinople, and made it, for the most part, a Christian city. The Byzantine Empire came into existence when in 395 the Roman Empire was divided between east and west.
In the seventh century the city was subject to almost annual attacks by Arabs that finally ended in 678. After the break in 1054 between the Roman Catholic and the Orthodox Eastern Churches, the patriarchate of Constantinople became the most powerful in the East. In the Middle Ages the city became the guardian of the inherited cultures of Greece and Rome and was much more advanced than western Europe in arts and literature. In 1204, however, Constantinople suffered a disaster when the French soldiers of the Fourth Crusade and their Venetian carriers decided to sack the rich city instead of continuing on to fight the Muslims in the Holy Land . They established the Latin Empire of Constantinople.
The Byzantine Empire divided into successor states, but in 1261 Michael VIII, emperor of Nicaea, recaptured the city and restored the empire. Meanwhile, the Ottoman Empire of Islamic Turks was increasing in power as the glory of the Byzantine Empire faded. By the mid-15th century Constantinople controlled no more than its immediate neighborhood. Nevertheless, when the Ottomon sultan Muhammad II laid siege to the city in 1453 it held out for 50 days, falling only when its ancient walls crumbled before the new Turkish artillery. Muhammad then moved his capital here and the city became known by its Turkish spelling as Istanbul. The fall of Constantinople, after its long history as defender of Christendom and Western culture, was so decisive an event that it was once taken by many as marking the end of the Middle Ages and the beginning of the Renaissance. Though many Greek scholars did flee the city with their precious manuscripts, cultural communication with the West had never ceased, and the Italian Renaissance is now seen to have begun a century earlier through Byzantine influences. In 1930, under Kemal Ataturk, the city was formally renamed Istanbul.