Khan Tervel breaks the Arab siege of Constantinople

On August 15, 718, the Arab siege of Constantinople ended following decisive military intervention by Bulgarian forces led by Khan Tervel. The intervention prevented the fall of the Byzantine capital and halted the Arab expansion into Southeast Europe.

In the autumn of 717, a massive Arab army launched a multi-pronged assault on Constantinople by land and sea. In response to the threat, Byzantine Emperor Leo III sent envoys to Khan Tervel requesting assistance. Despite ongoing conflicts between the young Bulgarian state and the Byzantine Empire, Tervel recognized that the Arab invasion posed a greater long-term threat to the region.

Bulgarian forces engaged the Arab army, which included a 20,000-strong unit commanded by Maslama ibn Abd al-Malik. The Bulgarians successfully disrupted Arab operations, contributing to a harsh winter where many invaders succumbed to hunger and disease. By the spring of 718, further Bulgarian military actions led to the final defeat of the land forces, forcing the Arab withdrawal from Constantinople.