Arab–Byzantine Siege of Constantinople (717–718)

Arab–Byzantine Siege of Constantinople (717–718)
Conflict	Siege of Constantinople (717–718)
Partof	Arab–Byzantine wars
Date	717–718
Place	Constantinople
Result	Byzantine victory
Combatant1	Umayyad Caliphate
Combatant2	Byzantine Empire
Commander1	Maslama ibn Abd al-Malik; Sulayman ibn Hisham; Caliph Umar II
Commander2	Leo III the Isaurian; Anastasios II; Theodore of Stoudios

Arab–Byzantine Siege of Constantinople (717–718) The siege of Constantinople in 717–718 was a decisive military confrontation during the Arab–Byzantine wars that halted Umayyad Caliphate expansion into Europe and preserved the Byzantine Empire. The conflict combined protracted land operations, a naval blockade, and complex diplomacy involving neighboring polities such as the Bulgarian Empire and the Papal States. The lifting of the siege marked a turning point in medieval geopolitics and influenced the careers of rulers including Maslama ibn Abd al-Malik and Leo III the Isaurian.

Background

In the early 8th century the Umayyad Caliphate pursued campaigns against Byzantine frontiers following setbacks at Tours and continued pressure in Anatolia, Syria, and Cilicia. The Byzantine–Islamic frontier had seen sieges of Antioch and raids on Thessalonica and Crete, while internal challenges within the Byzantine Empire—including dynastic change and the rise of Armenian and Isaurian factions—affected imperial readiness. Strategic considerations included control of the Bosphorus, access to the Aegean Sea, and securing approaches from Bithynia and Kyzikos toward Constantinople.

Prelude to the Siege

After Caliph Sulayman and successive commanders earmarked Constantinople as a primary objective, Maslama ibn Abd al-Malik assembled a large army in Syria and coordinated with an Umayyad fleet drawn from Alexandria and Antakya. Diplomatic maneuvers sought to isolate Constantinople by negotiating or coercing border lords such as the Themes and by testing defenses at Nicaea and Dorylaeum. Byzantine preparations under emerging leaders consolidated garrisons in Chrysopolis and stockpiled supplies in the imperial granaries, while envoys appealed to the Bulgarian Empire for assistance.

Course of the Siege

The besieging force established winter-quarters on the Sea of Marmara shores and constructed encampments at Hebdomon and Kouzounion. Assaults attempted to breach the land walls such as the Theodosian Walls and to exploit weaknesses near the Golden Gate. Byzantine sorties challenged Umayyad entrenchments and disrupted siege engines, while disease and logistics eroded the besiegers' capacity. Seasonal cycles and the arrival of Bulgarian auxiliaries under Tervel of Bulgaria shifted momentum as supply lines from Anatolia and Syria became precarious for the Umayyads.

Naval Operations and Blockade

A critical component was the Umayyad fleet seeking to enforce a blockade from the Sea of Marmara into the Bosphorus and to support amphibious landings on the Horn of the Golden Horn. The Byzantines employed Greek fire-equipped ships from the imperial navy based at Galikos and used maritime tactics developed during confrontations at Lesser Asia and Cyprus. Naval engagements around Pera and off Constantinople disrupted Umayyad logistics, while storms and shortages diminished the fleet's effectiveness. Control of maritime approaches ultimately determined the flow of reinforcements and food between the besiegers and their bases in Syria and Egypt.

Byzantine Defense and Leadership

Leadership from Leo III the Isaurian coordinated civil and military responses, integrating forces drawn from the Themes and elite tagmata such as units from Opsikion and Anatolikon. Commanders reinforced the Theodosian Walls, improved water and granary reserves, and executed counterattacks with experienced officers familiar from campaigns at Malazgirt and Sinope. The Byzantine use of Greek fire naval superiority, combined with strict discipline and fortification specialists from Constantinople's imperial administration, sustained the defense during harsh winters and plague outbreaks.

Arab Forces and Strategy

The Umayyad strategy under Maslama ibn Abd al-Malik relied on a multi-pronged investment combining siegecraft, field battles, and blockade, drawing contingents from Syria, Iraq, and Egypt. Siege engines, sappers, and cavalry raids probed the outer defenses at Bithynia and Pegae, while coordination with the Umayyad fleet aimed to isolate Constantinople. However, attrition from weather, shortages of forage, seasonal freezes in the Sea of Marmara, and resistance from border polities such as the Bulgarian Empire undermined Umayyad operational coherence. Command disputes and the broader priorities of the Umayyad Caliphate further limited sustained investment.

Aftermath and Consequences

The siege's failure reinforced Byzantine survival and contributed to the stabilization of Leo III the Isaurian's reign, influencing later policies including iconoclastic controversies and administrative reforms across the Themes and Anatolia. The setback curtailed Umayyad expansion into Balkan territories and preserved maritime routes to the Aegean Sea and Black Sea. Long-term outcomes included shifts in Umayyad strategic focus toward internal revolts and the Iberian Peninsula, evolving Byzantine naval doctrine, and renewed alliances with powers like the Bulgarian Empire and the Papal States. The siege remains a landmark in medieval history, shaping perceptions of resilience in Constantinople and altering the balance between Islamic and Christian polities in the eastern Mediterranean.

Category:Sieges of Constantinople