4 – The Umayyad Caliphate II (717 – 718)
After the failed siege, the Arabs retreated and what followed was a period of peace. Aside from having to recover after sustaining a huge number of losses, the Umayyad Caliphate found itself in the midst of the Second Muslim War. It was only after 692, when the Umayyad settled the issue, that hostilities between the Arabs and Byzantines resumed.
The beginning of the eighth century was a grim time for the Byzantine Empire as the Arabs started to make inroads. By 712, the Byzantine defenses appeared primed for a collapse, so the Arabs raided deeper and deeper into Asia Minor where they attacked and sacked enemy fortresses on the border. At that stage, the Arabs were taking full advantage of instability within the Byzantine Empire as the throne changed hands on multiple occasions within a few years of the deposition of Justinian II.
Eventually, the Arabs were ready for a full-scale assault on Constantinople which began in 717. They had at least 120,000 men and 1,800 ships while the Arab supply train featured 12,000 men, 6,000 camels, and 6,000 donkeys. Historians don’t know how many people defended the Byzantine capital, but they were significantly outnumbered by the Arabs. The Arabs devastated the countryside surrounding the city and began the siege in July or August. Arab sources claim that Emperor Leo III offered to pay one gold coin for every inhabitant of the city in a bid to get the invaders to leave.
The city appeared doomed as the determined besiegers had ample supplies but as the Arab navy failed to blockade the city, the Byzantines were able to hold firm. In hindsight, destroying the land near the city was a bad idea because when winter came, the Arabs suddenly found themselves struggling for provisions. The winter of 717/718 was particularly harsh and led to a famine amongst the besiegers. Disease ravaged the invaders, and they suffered tens of thousands of casualties.
In the spring of 718, two new Arab fleets arrived but promptly defected to the Byzantines as most of the crew were comprised of Christian Egyptians. Leo ordered an attack as soon as he heard the news and the Arab ships were destroyed; once again, the Byzantines used Greek Fire to great effect. With the city safe from a sea attack, a land army met the Muslims near Nicomedia and annihilated an Arab army. Up to 150,000 Arabs died in the failed attempt to take Constantinople.