Theodosian Walls

Walls of Constantinople
Istanbul, Turkey
Map showing Constantinople and its walls during the Byzantine era
Walls of Constantinople
Coordinates	41°00′44″N 28°58′34″E / 41.01224°N 28.976018°E / 41.01224; 28.976018
Type	Walls
Height	Up to 12 m
Site information
Owner	Turkey
Controlled by	Roman Empire, Byzantine Empire, Latin Empire, Ottoman Empire
Open to the public	Yes
Condition	Land walls partly ruined, restoration work under way; sea walls largely torn down
Site history
Built	4th–5th centuries, with later restorations and additions
Built by	Septimius Severus, Constantine I, Constantius II, Theodosius II, Heraclius, Leo V, Theophilos, Manuel I Komnenos, Justinian I
Materials	Limestone, brick
Battles/wars	Avar siege of 626, First and Second Arab sieges, Revolt of Thomas the Slav, Fourth Crusade, Second and final Ottoman siege
UNESCO World Heritage Site
Type	Cultural
Criteria	i, ii, iii, iv
Designated	1985 (9th session)
Part of	Historic Areas of Istanbul
Reference no.	356
State Party	Turkey
Region	Europe and North America

This article is part of the series on the military of the Byzantine Empire, 330–1453 AD
Structural history
Byzantine army: East Roman army, Middle Byzantine army (themes • tagmata • Hetaireia), Komnenian-era army (pronoia), Palaiologan-era army (allagia) • Varangian Guard • Generals (Magister militum • Domestic of the Schools • Grand Domestic • Stratopedarches • Protostrator)
Byzantine navy: Greek fire • Dromon • Admirals (Droungarios of the Fleet • Megas doux)
Campaign history
Lists of wars, revolts and civil wars, and battles
Strategy and tactics
Tactics • Siege warfare • Military manuals • Fortifications (Walls of Constantinople)
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Avar siege of 626, First and Second Arab sieges, Revolt of Thomas the Slav, Fourth Crusade, Second and final Ottoman siege

The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul in Turkey) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built.

Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, when well-manned, they were almost impregnable for any medieval besieger, saving the city, and the Byzantine Empire with it, during sieges from the Avars, Arabs, Rus', and Bulgars, among others. The advent of gunpowder siege cannons rendered the fortifications vulnerable, but cannon technology was not sufficiently advanced to capture the city on its own, and the walls could be repaired between reloading. Ultimately the city fell from sheer weight of numbers of the Ottoman forces on 29 May 1453 after a six-week siege.