Siege of Constantinople (717–718)

In 717–718, Constantinople, the capital of the Byzantine Empire, was besieged by the Muslim Arabs of the Umayyad Caliphate. The campaign marked the culmination of twenty years of attacks and progressive Arab occupation of the Byzantine borderlands, while Byzantine strength was sapped by prolonged internal turmoil.

Source: Wikipedia — Siege of Constantinople (717–718) (CC BY-SA 4.0)