The Battle of Kleidion took place on July 29, 1014, between the Byzantine Empire and the Bulgarian Empire. It was the culmination of the nearly half-century struggle between the Byzantine Emperor Basil II and the Bulgarian Emperor Samuel in the late 10th and early 11th centuries. The result was a decisive Byzantine victory.

The First Bulgarian Empire was a medieval state that existed in Southeastern Europe between the 7th and 11th centuries AD. It was founded in 680–681 after part of the Bulgars, led by Asparuh, moved south to the northeastern Balkans. There they secured Byzantine recognition of their right to settle south of the Danube by defeating – possibly with the help of local South Slavic tribes – the Byzantine army led by Constantine IV. During the 9th and 10th century, Bulgaria at the height of its power spread from the Danube Bend to the Black Sea and from the Dnieper River to the Adriatic Sea and became an important power in the region competing with the Byzantine Empire.