The hopeless Second Arab Siege of Constantinople in 718

15 August 718, by order of the Caliph, the hopeless Second Arab Siege of Constantinople was raised after a year, marking a decisive victory of the Eastern Roman Empire over the Umayyad Caliphate.

“In the two sieges, the deliverance of Constantinople may be chiefly ascribed to the novelty, the terrors, and the real efficacy of the Greek fire. The important secret of compounding and directing this artificial flame was imparted by Callinicus, a native of Heliopolis in Syria, who deserted from the service of the caliph to that of the emperor. The skill of a chemist and engineer was equivalent to the succor of fleets and armies; and this discovery or improvement of the military art was fortunately reserved for the distressful period, when the degenerate Romans of the East were incapable of contending with the warlike enthusiasm and youthful vigor of the Saracens (Edward Gibbon “The History of the Decline and Fall of the Roman Empire”)

A sally of Byzantine cavalry during the Siege of Constantinople (from the 14th century Manasses Chronicle)

Rome’s charming tradition of being her own greatest enemy seamlessly continued into the Byzantine epoch of her long history. After the exhaustion of the world war with the Persian Sassanids that left both empires open like a barn door to the onslaught of the Arab Muslims in mid-7th century, the threat to the very existence of the Eastern Rome was far from being over in the early 700s. The Near East and Mesopotamia were already lost, Egypt was conquered by the Arabs and Carthage, the last Byzantine outpost in northern Africa, had fallen in 695. And while a capture of Constantinople could be averted only so in 678 and the Umayyad Caliphate pushed into Spain, the Indus valley and, again and again, into Byzantine territory in Asia Minor, the Romans had nothing better to do than pondering the legitimacy of icon worship and change their emperor nine times between 685 and 717, mostly due to various civic and military revolts. And by then, Caliph Sulayman bin Abd al-Malik already had a second major expedition launched towards the Bosporus, more than 100,000 men, well provisioned and equipped, along with 2,500 ships, ready to conquer Constantinople.

One of the few images showing the use of Greek Fire from the 12th century chronicle of John Skylitzes, now at Madrid.

The Umayyads had backed the wrong horse, though. The latest addition to Rome’s list of emperors, the scion of fierce Taurus mountain tribesmen from Isauria, Leo III, had negotiated with Sulayman, even to the prospect of Rome becoming a vassal state of the Caliphate, was finally refused. Now Leo proved to be a more than able defender. And while the Arab army under their commander Maslama ibn Abd al-Malik began to lay siege to the Roman capital, their navy was badly cut up by the Byzantines who still had the edge in weapon technology at sea. Under the personal command of the new emperor, the Arab ships were set ablaze squadron by squadron with the infamous “Greek Fire”, a highly incendiary liquid, probably a combination of pine resin, naphtha, quicklime, sulphur, or niter, that continued to burn on water and was shot on enemy vessels by highly trained crews, the siphonarioi, with pressurised nozzles, the so-called siphons. Along with the mighty chain that closed the entrance to the Golden Horn for ships quite thoroughly, the city was never fully cut off from supplies, while the once well supplied besiegers had to bring their provisons through enemy country during a particularly harsh winter. When a naval relief expedition from Egypt was completely wiped out by the Byzantines during the following spring and Byzantine diplomacy had convinced their Bulgar arch-enemies that the Arabs were a far greater threat and persuaded the Bulgar Khan Tervel to fight for them, General Maslama with his cut-off, starved and disease-ridden army was in over his head.

"The Virgin descended with a company of saints and spread out her mantle to deflect the blows. God caused the Christian defenders to kill their opponents." - A scene from the siege of Constantinople illustrated in the 13th century "Cantigas de Santa Maria"

On the day of the Assumption of Mary, Maslama called the whole thing off and withdrew with the remains of his forces towards the Euphrates. Constantinople’s walls had held and to the Byzantines, their victory was ascribed to their patron saint, the Theotokos, the Birth-Giver of God. Her most venerated icon, the hodegetria of Mary, was displayed as it had been during other sieges, that of the Sassanids, the Avars and the first Arab foray, when the Virgin had held her hand over her city. It was the last Arab attempt to conquer Constantinople and its potential fall in a distant future assumed eschatologic proportions, the conquest being postponed to the end of days. But with the victories of the Franks in the West at Toulouse in 721 and 732 at Tours, the failed siege of Constantinople was a sure sign that the critical high water mark of the Umayyad expansion was passed for Europe.