Constantinople

Ancient city founded by the Greeks as Byzantium in about 660 BC and refounded by the Roman emperor Constantine (I) the Great in AD 330 as the capital of the Eastern Roman Empire. Constantinople (modern Istanbul, Turkey) was the impregnable bastion of the Eastern Roman Empire and the Byzantine Empire, its successor, until it fell to the Turks on 29 May 1453 after a nearly two‐month siege and became the capital of the Ottoman Empire.

For over a thousand years the walls established by the emperors of Rome and of the Eastern Empire defended the city against all assailants. Nothing is known of the early defences before Constantine began construction of fortifications to protect his new capital; these ran in an exterior arc from the present‐day Atatürk Bridge to the Istanbul Hospital, but have not survived.

The emperor Theodosius II (reigned 408–50) began construction of a new land wall 6 km/3.7 mi long, 1.3 km/0.8 mi west of Constantine's fortifications. These new walls, improved and enlarged during Theodosius' reign, became the basis of Constantinople's defence. Consisting of an inner and outer wall with a deep moat in front, the two walls were of descending height, allowing artillery fire to be directed from both. The inner wall was fortified by 96 towers and had 8 main gates as well as several posterns. Walls were also constructed along the seashore, completely enclosing the city. In about 510 the Long Wall was constructed 65 km/40 mi to the west, but at over 45 km/28 mi in length it was impractical to defend and it was abandoned in the 7th century.