Which Arab siege of Constantinople was repelled in 718?

The Second Arab Siege of Constantinople was repelled in 718. The Umayyad Caliphate launched the campaign in 717 under Maslama ibn Abd al-Malik, hoping to capture the Byzantine capital and cripple the empire. The attack followed decades of Arab-Byzantine warfare and was more serious than the earlier siege of 674–678.

Constantinople’s Theodosian Walls resisted the land assault, while the Byzantine navy used Greek fire against the Arab fleet. This kept the city supplied by sea and prevented a complete blockade. A harsh winter brought famine and disease to the besieging army, while Byzantine forces also defeated Arab reinforcements.

Bulgar forces under Khan Tervel attacked the Arabs from the rear, adding further pressure. After roughly thirteen months, the Umayyad army withdrew on 15 August 718. The retreating fleet suffered additional losses from storms and other disasters.

This defeat was a major turning point. The Arab caliphate abandoned its immediate goal of conquering Constantinople, helping preserve the Byzantine Empire and delaying Muslim expansion into southeastern Europe for centuries. It is often confused with the First Arab Siege, which took place from 674 to 678.