All these factors — Umayyad consolidation of Muslim power in Damascus, a slowing down of the conquests in general, and the need to direct the bellicosity of the various idle or disgruntled warlike Muslim sects, not to mention an undying enmity for the obstinate infidels across the way — encouraged the caliphate to apply its full might against its arch-foe. Constantinople had been unsuccessfully besieged several times before, most notably during the First Siege, which lasted four years (674–78) and was ultimately turned back by the cyclopean walls of the city.
So it was that, upon his ascension to the caliphate in 715, the new supreme leader of the Islamic empire, Suleiman, decided that the time was ripe for a massive, all-out offensive against Constantinople. The Byzantines would go on to offer a hefty tribute, but nothing less than total capitulation to Islam would do. Mustering a mammoth army of some 200,000 fighters, with Suleiman’s own brother, Maslama, leading, the former commanded the latter: “Stay there [Constantinople] until you conquer it or I recall you.” (That a caliph sent his own brother is further indicative of the importance of this campaign.)
A single anecdote supports the chroniclers’ claims that a gargantuan army was being mustered. Two years prior to the siege, in 715, a report reached the Christians that the Muslims were felling countless trees in Lebanon, land of the cedar, in order to construct tens of thousands of warships for an “upcoming expedition.” This fact alone caused a mini-war to erupt on the island of Rhodes, where the Byzantines sent an army to intercept the Muslim expeditionary force. One Byzantine ambassador returning from Damascus reported that the “Saracens were preparing an armament by sea and land, such as would transcend the experience of the past, or the belief of the present.” In short, 120,000 infantry and cavalry, and a naval force composed of 80,000, were making their way to Constantinople.
Maslama, leading the land force through Anatolia, crushed and put to the sword all in his way. Women and children were enslaved; tens of thousands of men crucified. While making their way through that great desolate no-man’s land between the Byzantine and Umayyad empires, frequented by nomadic tribes, the Muslims attacked, slew, and burned all in their path.
According to renowned Muslim chronicler al-Tabari, “The [Christian] inhabitants of eastern Anatolia were filled with terror the likes of which they had never experienced before. All they saw were Muslims in their midst shouting ‘Allahu Akbar!’ Allah planted terror in their hearts. . . . The men were crucified over the course of 24 km.” Al-Tabari later goes on to explain that the Muslim forces were successful owing to their adherence to Koranic verses such as 8:60: “Muster against them [infidels] all the men and cavalry at your command, that you may strike terror into the hearts of the enemies of Allah, and your enemies.” (See also 3:151.) (Nearly a millennium and a half after the Koran’s compilation, modern-day mujahidin — “holy warriors” who are fond of exhorting their followers by referring to these otherwise arcane battles — continue relying on such verses and their exegeses to “terrorize” the “enemies of Allah.”)
To make matters worse, as Maslama was marching toward Constantinople, subjugating everything in his path, the Christian empire itself was internally divided — as evinced by the fact that, between 713 and 717, two emperors had come and gone.
Enter Leo III — also known as Leo the Isaurian, Leo the Arab, and, most notoriously, Leo the Heretic. There is little doubt that the Byzantine victory over the Muslims owes a great debt to Leo, who makes his appearance early in the pages of the chronicles as a general and strategist — living up to the Greek word for “general,” strategos.
Born as Conon in modern-day Syria (hence the “Arab” appellation), Leo, stationed in Anatolia, encountered the forces of Maslama early on. All the sources record Leo playing something of a cat-and-mouse game with the caliph’s brother, duping him in various ways. Tabari simply concludes that Leo dealt Maslama “such a deception as if he [Maslama] was a silly plaything of a woman.”
At any rate, Leo gained the necessary time and advantage to slip back to Constantinople, where, as the ablest man to defend the empire from the coming onslaught, he was soon proclaimed emperor. Considering the empire’s strong walls that had withstood countless sieges for centuries, Leo knew that, as long as sea communications were open, the city would be relatively safe. The problem was that, as Maslama was nearing with his land force of 120,000, 1,800 vessels containing the additional 80,000 fighting men were approaching the Bosporus. The city would be surrounded.