Forces of the Umayyad Caliphate abandoned a year-long siege of Constantinople, ending their goal of conquering the Byzantine Empire.

The Umayyad Caliphate or Umayyad Empire was the second caliphate established after the death of the Islamic prophet Muhammad and was ruled by the Umayyad dynasty. Uthman ibn Affan, the third of the Rashidun caliphs, was also a member of the clan. The family established dynastic, hereditary rule with Mu'awiya I, the long-time governor of Greater Syria, who became caliph after the end of the First Fitna in 661. After Mu'awiya's death in 680, conflicts over the succession resulted in the Second Fitna, and power eventually fell to Marwan I, from another branch of the clan. Syria remained the Umayyads' main power base thereafter, with Damascus as their capital.

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. In 716, after years of preparations, the Arabs, led by Maslama ibn Abd al-Malik, invaded Byzantine Asia Minor. The Arabs initially hoped to exploit Byzantine civil strife and made common cause with the general Leo III the Isaurian, who had risen up against Emperor Theodosius III. Leo, however, deceived them and secured the Byzantine throne for himself.

The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the events that caused the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'.