The Siege of Constantinople, 717-718 AD – The Use of Naval Power

By Andrew Latham and Rand Lee Brown II

“[They] began blowing with smiths’ bellows at a furnace in which there was fire and there came from it a great din. There stood there also a brass [or bronze] tube and from it flew much fire against one ship, and it burned up in a short time so that all of it became white ashes…” ~ a possible eyewitness account of Greek Fire from the 12th-century Norse saga, Yngvars saga víðförla

Although many still believe that the Roman imperial order collapsed with the fall of the Western Empire in 476, in reality, it continued on for almost another millennia in the form of the Eastern Roman (or Byzantine) Empire. From their palaces in the famed city of Constantinople, the Byzantine emperors attempted to preserve the imperial remnant in the face of mounting challenges from all sides.


Crucial to this imperial project was maintaining control over the eastern half of the Mediterranean. Continuing the naval traditions inherited from their predecessors of the Classical Era, the Eastern Empire was almost alone in producing and deploying dedicated fleets of warships – mostly consisting of sleek and swift dromons, a moderately improved version of the older Roman liburnae galleys. And exploiting this technological edge, the Byzantines deployed fleets that allowed them to exercised considerable control over the vast amounts of trade and wealth that continued to flow from Asia into Europe via their sea lanes. This initial Byzantine advantage, however, did long go unchallenged.

Map of the main Byzantine-Muslim naval operations and battles in the Mediterranean, 7th–11th centuries – image by Cplakidas / Wikimedia Commons

In the seventh century, the Islamic Conquests burst out of Arabia like a sandstorm, devouring almost every other nation on their periphery for nearly a century, including the Byzantine provinces of Egypt, the Levant, and Syria. Proving themselves remarkably adaptable, the Arab caliphates began building and deploying fleets of their own and established themselves as dangerous competitors for control of the Mediterranean.  Soon, there was not a coast within the Middle Sea that did not experience Arab sea raids or piracy.

In the early years of the eighth century, the head of the Umayyad Caliphate, Sulayman ibn Abd al-Malik, sought to escalate Arab ambitions even further and dispatched a massive army with an accompanying fleet to capture Constantinople itself. Although Arabs had attempted such a move before and failed, Sulayman was convinced this time would be different, taking advantage of a prolonged period of internal civil conflict and imperial coups within the Eastern Empire – those two being the perennial weaknesses of the Byzantine state. The army, numbering potentially in the tens or even hundreds of thousands, would lay siege to the city by land on its western front and the fleet would blockade its eastern approaches via the sea in the Hellespont. The Arab forces were in place before the walls of Constantinople by the year 717.


However, almost from the start, the tide went against the Arabs. Right before the siege began, the Imperial Crown came to rest on the brow of the extremely capable Leo III, who brilliantly prepared his new capital city for the impending siege. Rapidly making alliances with key powers within and without the Empire, marshaling Roman forces to fortify pivotal avenues of approach in the Aegean and Asia Minor, and ensuring each citizen stockpiled three years of supplies within the city itself, Leo was more than ready to face the Arab onslaught.

The defenses on the landward side of Constantinople were legendary, consisting of the famed triple-layered Theodosian Walls built by their namesake, Theodosius II, in the fifth century. The Arab army was remarkably short on siege equipment and seemed to rely solely on the tactic of starving out the city by means of a joint land and sea blockade.

On 3 September 717, the Arab commander, Maslama, ordered his fleet to reposition farther up into the Hellespont to cover the Golden Horn and the Byzantine sea lanes coming from the Black Sea. As the Arab ships made their way north, their inexperienced sailors lost the wind and slowed to a confused gaggle right at the entrance to the Golden Horn. Leo seized this moment and launched his trump card – a fully armed Byzantine fleet hiding in the Golden Horn equipped with the terrifying secret incendiary weapon named for its inventors, Greek Fire. Taken on the flank and caught completely by surprise, the Arabs lost twenty ships with all hands in an instant to the napalm-like substance that the Byzantines had developed to jet out in a directed stream from bronze siphons on their ships like described above in the quotation. The survivors scattered southward, abandoning the waters to the Byzantines for the rest of the siege.


From there, the fortunes of the besieging Arabs went from bad to worse. Two resupply fleets met the same fate as the first, and the Arab army found itself dying of disease and starvation before the impregnable walls of Constantinople in a particularly harsh Thracian winter. The situation became so desperate for them that, according to Theophanes the Confessor – the main primary source for the siege – the besiegers resorted to eating their pack animals, plant sprouts, feces, and even their own dead. Finally, an army of Bulgars allied with Leo descended upon the Arabs and slaughtered them nearly to a man. Of the fleet of hundreds of vessels that the Arabs dispatched, allegedly only five returned.

The year 718 would mark the final Arab attempt to take the fabled city of Constantinople, such an outcome due in no small part to the actions of the Imperial Navy and their horrific Greek Fire. Three decades later, the Umayyad Caliphate would collapse and give way to the Abbasids, who relocated their capital from Damascus to Baghdad and never again substantially challenged Byzantine maritime power.

Despite playing such a pivotal and dramatic role repeatedly in Byzantine naval warfare, there exists no clear idea of what exactly Greek Fire was or how it was made – its creators taking the finer details of their prized secret weapon with them to their tombs. It was obviously some sort of petroleum-based compound that could be directed in an ignited liquified stream through siphon mechanisms installed at the prows of specialized warships built for that purpose.


Some historians debate the importance of Greek Fire and question its role in securing Byzantine maritime success during that period. These would argue that it was, in fact, merely their continuation of Classical Roman naval organization and professional traditions that truly enabled the Eastern Roman Empire to project sea power into the Mediterranean.  Whatever the case, the Imperial Navy was possibly the most formidable naval force roaming the Mediterranean in the early centuries of the medieval era and many challengers were sent to the bottom in a literal weaponized firestorm.

Dr. Andrew Latham is a professor of political science at Macalester College in Saint Paul, Minnesota. He is the author, most recently, of a monograph entitled Medieval Sovereignty, to be published in 2020 by ARC Humanities Press.  You can visit Andrew’s website at or follow Andrew on Twitter @aalatham

Rand Lee Brown II is a recently retired officer in the United States Marine Corps. Holding a Master of Arts degree in Military History from Norwich University with a focus on medieval warfare, he has written on military history for a variety of forums, including the Marine Corps Gazette and

Click here to read more from Andrew and Rand

Further Reading:

Stanton, Charles D.  Medieval Maritime Warfare (Pen & Sword Books, 2015)

Whittow, Mark.  The Making of Byzantium 600-1025 (University of California Press, 1995)

Top Image: Image from the Madrid Skylitzes, showing Greek Fire in use against the fleet of the rebel Thomas the Slav



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