Siege of Constantinople 717–718: How Byzantium Survived the Umayyad Assault

In 717, a massive Umayyad army and fleet arrived outside Constantinople intending to end the Byzantine Empire. One year later, Constantinople was still standing—and the besieging army was withdrawing. #ThronewakeAtlas #SiegeOfConstantinople #Constantinople #ByzantineEmpire The Siege of Constantinople, 717–718, became one of the most consequential military confrontations of the early medieval world. The Byzantine Empire had already lost Syria, Palestine, and Egypt. Political instability had shaken Constantinople for decades. Emperor *Leo III* had been on the throne for only months when forces commanded by *Maslama ibn Abd al-Malik* reached the city's defenses. Yet Constantinople possessed advantages generations in the making. The enormous *Theodosian Walls* protected its landward approach. Vast cisterns stored water beneath the city. Granaries helped sustain the population. Byzantine warships challenged attempts to blockade the Bosporus, while the famous incendiary weapon commonly called *Greek fire* made close naval operations extraordinarily dangerous. But Greek fire alone did not decide the siege. The winter of 717–718 placed enormous pressure on the besieging army. Supply lines deteriorated. Bulgar forces threatened the Umayyad rear in Thrace. Reinforcement fleets from Egypt and North Africa failed to establish control of the sea, while land reinforcements crossing Anatolia were intercepted. By the summer of 718, the entire logic of the siege had reversed. The army that came to isolate Constantinople was itself struggling for supplies and reinforcement. On August 15, 718, according to the Byzantine chronological tradition, the great expedition finally withdrew. But what actually saved Constantinople? Was it the Theodosian Walls? Greek fire? Emperor Leo III? The Byzantine fleet? The brutal winter? The Bulgars? Failed Umayyad logistics? Or was victory possible only because all of these factors worked together? This documentary follows the campaign from the political crisis before the siege to the final withdrawal, separating later legend from what the surviving Byzantine, Arabic, Syriac, archaeological, and documentary evidence can reasonably support. Discover: • Why Constantinople was almost impossible to blockade • How Leo III prepared for the approaching invasion • Why Maslama's strategy depended on controlling the sea • How the Theodosian Walls shaped the campaign • What Greek fire actually contributed • Why the winter of 717–718 became disastrous • How the Bulgars threatened the besieging army • Why Umayyad reinforcement fleets failed • How supply and logistics became decisive • Why Constantinople survived when so much of the Byzantine Empire had already been lost • What changed after the siege—and what did not The siege did not destroy the Umayyad Caliphate, end Byzantine-Arab warfare, or single-handedly “save Western civilization.” Its real history is more complicated—and far more interesting. Welcome to **Thronewake Atlas**, exploring emperors, collapsing kingdoms, decisive sieges, political struggles, forgotten campaigns, and the turning points that reshaped the ancient and medieval worlds. Subscribe to *Thronewake Atlas* for more cinematic historical documentaries. -------------------------------------------------- Siege of Constantinople 717 718, Constantinople 717, Constantinople 718, Second Arab Siege of Constantinople, siege of Constantinople documentary, Byzantine Empire, Byzantine history, Leo III, Leo III Byzantine emperor, Maslama ibn Abd al-Malik, Maslama Constantinople, Umayyad Caliphate, Umayyad Empire, Umayyad siege Constantinople, Arab Byzantine wars, Byzantine Arab wars, Greek fire, Greek fire Constantinople, Theodosian Walls, walls of Constantinople, Byzantine navy, Byzantine military history, medieval Constantinople, Constantinople history, Constantinople siege, First Bulgarian Empire, Khan Tervel, Bulgars Constantinople, winter 717 718, Bosporus history, Byzantine warfare, early medieval warfare, medieval siege warfare, ancient siege documentary, historical documentary, military history documentary, Byzantine documentary, Umayyad history, Leo the Isaurian, Thronewake Atlas