Enter Leo the Isaurian
A man named Conon was set to change the course of history. He was an excellent soldier and commander and in 716, he became the leader of the Anatolian theme army. He became known as Leo the Isaurian and in 717, with the backing of the military, the general was crowned Emperor Leo III. To be fair, it wasn’t a normal usurpation. Leo negotiated with Theodosius III and Patriarch Germanos and the emperor was seemingly happy to step aside and let someone else handle the crisis. Leo agreed not to disturb the church and he allowed Theodosius to retire and become a monk.
Once in power, Leo quickly went to work because he knew the Arab invasion was imminent. Leo stored extra food, prepared the navy, and further strengthened Constantinople’s already impressive fortifications. The Byzantines were ready and in August 717, Maslama was given command of the Arab forces and marched through Anatolia to the city walls. The size of the invading force varies according to the source. al-Masudi, an Arab writer in the 10th century, said there were 120,000 troops but Michael the Syrian, a 12th-century Syrian writer, claimed there were 200,000 Arabs. According to Theophanes the Confessor, the invaders had 1,800 ships.
“The Cruelest Winter that Anyone Could Remember”
These are the words of English historian John Julius Norwich although the Arab invaders probably thought it wouldn’t come to that when they launched their August invasion. However, the siege lasted for a year as the Muslims tried and failed to breach the stubborn Byzantine defense. Maslama ordered an attack on the walls as soon as his army arrived in August but the defenders had no problem in beating it back. The Arab commander quickly realized that continued frontal assaults were pointless so he ordered his men to dig trenches to prevent the Byzantines leaving the city.
As a consequence, much of the early fighting took place in the sea and Admiral Suleiman led part of his navy on the Hellespont. When the ships approached the city, a fast current took them by surprise and caused chaos. Leo spotted the difficulty of the enemy and took advantage by lowering the chain that protected the Golden Horn and swiftly attacking the Muslim ships before they could get in formation. With the aid of Greek Fire, the Byzantine fleet destroyed and captured a significant number of ships. Sulieman knew that another setback of that nature would destroy his fleet so he didn’t want to sail past the city.
The bad news kept on coming for the invaders; they learned that Caliph Sulayman had died from a stomach complaint and was replaced by Umar II, a man not renowned for his military prowess. To make matters worse, the Bulgars were making their presence felt and in autumn, they began attacking the Arabs on the West side of the Bosporus. The Bulgars massacred any Arab camp they found and their success tempted the Byzantines into opening their gates to try and break the siege. However, they were halted at the Arab trenches and retreated back into Constantinople. If the Muslim army thought their luck would change during the winter, they were sorely mistaken.