Constantinople was founded by Emperor Constantine the Great in 333 AD as the "New Rome,” but after the sack of the old Rome in 410 it became the Only Rome (so far as the emperor was concerned). The capital of the Roman Empire was now on the Bosphorus.
The city of Byzantium was chosen to be the capitol of the Eastern Roman Empire. Sixty five years later, however, the name of the city was changed to Constantinople in honor of its founder, Constantine. At the time, the Byzantine empire was known as simply Roman, with Roman subjects. Scholars have named it the Byzantine Empire after its ancient capital name Byzantanium. Greek was the predominant Language spoken there; even a selection of its populations spoke Latin, Coptic, Syriac, Armenian, and other languages.
Even though this radical change was made in the concept of the empire, the Byzantines always referred to themselves during their one thousand year long history as the Roman Empire and their nation as the Nation of Rome. After the collapse of the empire, however, historians began to refer to this empire as the "Byzantine" Empire and so it is remembered today.
With the founding of Constantinople, the older culture effectively absorbed its vigorous younger challenger. Even the name Constantinopolis is Greek (polis meaning city). The main problems in the past century had been defending the Balkans from invaders beyond the Danube and protecting the Middle East from the Persians. Byzantium, renewed as Constantinople, sat firmly between these troubled regions.
The Crusader armies of Europe marched through in the 12th and 13th centuries, doing battle with the Seljuks as well as threatening and in 1204 even attacking, conquering and sacking Constantinople.
The immediate result of the disturbance at Constantinople politically was the approval and signing by the Sultan of the scheme approved by the embassies for reforms in Turkey by the Sultan. This aroused great opposition among the Moslems in Constantinople and corresponding delight throughout the empire.
The Fall of Constantinople was the conquest of that Greek city by the Ottoman Empire under the command of Sultan Mehmet II, on Tuesday, May 29, 1453. This marked not only the final destruction of the Eastern Roman ("Byzantine") Empire, and the death of Constantine XI, the last Roman Emperor, but the strategic conquest crucial for Ottoman hegemony over the Eastern Mediterranean and Balkans.
The Decline of the Byzantine Empire was said to have been hastened by the Crusades, even though they did recover some lands of Asia Minor during that time period. During the 12th Century, the political and military power declined steadily, and the Crusaders allied with Venice seized and plundered Constantinople in 1204, establishing their own empire of Constantinople.
Emperor Michael VIII Palaeologus recaptured Constantinople from the Latins in 1261, and ruled there until 1453. The new Palaeologan Empire barely survived for a short period, and the emergent Ottoman Turks conquered remnants of Byzantine Asia Minor, overran the Balkans, and eventually took Constantinople. The Byzantine Empire, in 1453, was brought to an end.