Siege of Constantinople

Siege of Constantinople
Conflict	Siege of Constantinople (717–718)
Partof	Byzantine–Arab wars
Date	717–718
Place	Constantinople
Result	Byzantine victory
Combatant1	Umayyad Caliphate
Combatant2	Byzantine Empire
Commander1	Maslama ibn Abd al-Malik; Sulayman ibn Hisham
Commander2	Leo III the Isaurian; Emperor Anastasius II (pre-siege preparations); Patriarch Germanus I
Strength1	~80,000 (land); fleet ~1,800 ships (contemporary claims)
Strength2	garrison ~12,000; fleet limited but supported by Byzantine navy and Bulgar Khanate allies
Casualties1	heavy from starvation, disease, Byzantine Greek fire losses
Casualties2	moderate

Siege of Constantinople

The siege of Constantinople (717–718) was the culminating attempt by the Umayyad Caliphate to capture Constantinople and decisively defeat the Byzantine Empire during the Umayyad invasion of Anatolia. Combining a massive land army under Maslama ibn Abd al-Malik with a seaborne fleet, the campaign was checked by the reformed forces and fortifications of the Byzantines under Leo III the Isaurian, aided by diplomatic ties with the First Bulgarian Empire and tactical use of Greek fire. The failure of the siege reshaped the balance between Islamic caliphates and Eastern Roman polities and influenced subsequent interactions across the Aegean Sea and Black Sea.

Background and strategic context

In the early 8th century the Umayyad Caliphate pursued expansion eastward and westward, culminating in repeated expeditions against Byzantium such as the 704–705 raids and the 717 campaign. The accession of Caliph Sulayman ibn Abd al-Malik and the appointment of Maslama ibn Abd al-Malik followed earlier clashes at Constantinople in 674–678 and at the Battle of Sebastopolis. Byzantium’s internal politics—episodes involving Philippikos Bardanes, Anastasius II, and the rise of Leo III—intersected with Arab ambitions, while frontier pressures around Anatolia, Cilicia, and Bithynia made the capital a focal point. The wider milieu included the northern threat from the First Bulgarian Empire under Krum’s successors, shifting loyalties among Armenian princes like Grigor II, and the strategic maritime contest for control of the Marmara Sea and the Bosporus Strait.

Forces and fortifications

The Umayyad expeditionary force assembled in Syria and Melitene combined cavalry contingents, infantry levies, and a large fleet drawn from Alexandria, Tarsus, and Levantine ports, commanded by Sulayman ibn Hisham at sea and Maslama on land. Byzantine defenses centered on the Theodosian Walls, sea walls along the Golden Horn, and naval squadrons based at Hellespont and Sea of Marmara yards, improved after earlier sieges by emperors including Justinian I and recent repairs credited to Anastasius II. The garrison comprised themes’ troops from Opsikion, Anatolikon, and imperial tagmata, reinforced by mercenary contingents and naval crews schooled in Greek fire manufacture and deployment techniques traceable to engineers like Callinicus of Heliopolis. Logistics also involved grain stocks from Thrace and support from Bulgaria negotiated by envoys.

Course of the siege

Maslama’s army arrived and established a blockade around Constantinople in late 717, while the Umayyad fleet attempted to impose a maritime cordon. The Byzantines, under Leo III the Isaurian, refused open battle and relied on sorties, fortified defense, and naval interdiction. Harsh winter conditions, supply shortages, and outbreaks of disease decimated the besiegers; contemporaneous accounts reference a catastrophic storm that struck the Umayyad fleet, reminiscent of losses at the Battle of the Masts era, while Byzantine use of Greek fire inflicted further damage. The intervention of the Bulgar Khanate—led by rulers in dynastic continuity with Tervel’s legacy—and diplomatic maneuvers with Pope Gregory II and western polities undermined Umayyad plans. By summer 718, successive failures, depleted resources, and the arrival of Byzantine reinforcements forced Maslama to lift the siege.

Siege technologies and tactics

The campaign saw a synthesis of late antique and early medieval siegecraft: Umayyad engineers employed traditional siege engines—mangonels, battering rams, and scaling towers—adapted from experiences in sieges of Constantinople and fortresses such as Sinope and Anazarbus. Naval tactics included blockades, boarding actions, and attempts to isolate the city’s sea lanes at the Golden Horn. Byzantines exploited the Theodosian Walls’ layered defenses, counter-mining, and the incendiary advantage of Greek fire, deployed from chelandia and siphons aboard dromons and at tower embrasures; these technologies had precedent in earlier naval encounters with Arab fleets and innovations associated with Syrian engineers. Logistics, winter attrition, and control of supply routes—through Thrace and across the Aegean Sea—proved as decisive as siege engines.

Political and diplomatic consequences

The failed siege curtailed Umayyad momentum and contributed to shifts within Umayyad political circles, affecting succession dynamics after Caliph Sulayman’s death and influencing frontier policy in Armenia and Caucasus provinces. For Byzantium, Leo III’s reputation solidified, enabling administrative and military reforms in the theme system and doctrinal controversies like the later Iconoclasm debates to unfold under his aegis. The Byzantine alliance with the First Bulgarian Empire reinforced Balkan geopolitics and altered trade flows through the Black Sea littoral. The respite allowed by the victory affected relations with Abbasid successors and set precedents for future engagements such as the Battle of Akroinon and naval clashes near Lemnos.

Aftermath and legacy

The siege’s failure marked a strategic reversal for the Umayyad Caliphate and preserved Constantinople as a linchpin of Eastern Roman resilience, shaping medieval Mediterranean geopolitics. It catalyzed military reforms that sustained Byzantine endurance into the 8th century and symbolically entered Byzantine, Arab, and Bulgarian chronicle traditions, cited in works by chroniclers like Theophanes the Confessor, al-Tabari, and later historians of Byzantium. Archaeological traces of the period—remnants along the Theodosian Walls, shipwrecks in the Marmara Sea, and material culture from Constantinople’s hinterlands—inform modern scholarship, influencing studies in medieval naval warfare, siegecraft, and imperial administration. The siege remains a pivotal episode linking the histories of Islamic expansion, Byzantine resilience, and Slavic-Bulgar interactions in the early medieval Mediterranean.

Category:Sieges of Constantinople Category:8th century in the Byzantine Empire Category:Umayyad Caliphate military history