Battle of Sebastopolis

The Battle of Sebastopolis was fought at Sebastopolis¹ in the middle of the Armeniac Theme in 692 CE between the Byzantine Empire and the Umayyad Caliphate. With this battle, the long-standing peace between the two powers, established in 680, came to an end.

Justinian II sought to restore the territorial extent of the Roman Empire under Justinian I by pursuing military campaigns that reversed the policies of his father, Constantine IV. Early on, he broke a treaty with the Bulgarians and attacked Slavic tribes near Thessaloniki, resettling many in the Opsician Theme and enrolling them in a new corps under Neboulos. Later, tensions with the Umayyads increased after Justinian II undermined an existing treaty and prepared for war. However, the long preparation by the Byzantines gave sufficient time for the Umayyads to assemble an army and invade Byzantine territories.

The Byzantine army, led by Leontios, met the forces of Muhammad ibn Marwan near Sebastopolis in the Armeniac Theme. The Umayyads used texts of the broken treaty as their flag to display the justice of their cause. The Byzantines initially had the advantage in the battle, however, Neboulos and a significant portion of the Slavic troops defected to the Umayyad side, presumably bribed by Muhammad ibn Marwan. The desertion caused a Byzantine defeat. Following this, Justinian punished the remaining Slavic troops harshly, while the Umayyads resumed raids into Byzantine territory.

Background

Early in his reign, Justinian II had the ambition to restore the lands of the former Roman Empire, as Emperor Justinian I had during his reign. To accomplish this goal, he sought combat by undoing measures established by his father. Early on, he broke peace with the Bulgarians and immediately attacked Slavic tribes that had established themselves near Thessaloniki. In 688/9, Justinian II transplanted from the and settled them in the , which had been depopulated from Arab attacks under the father of Justinian's reign. He granted them military , and from them he recruited a special military corps, allegedly 30,000 strong, called "the chosen people" (: λαὸς περιούσιος), which meant that this population would have a particular function to fulfill under the emperor's direction, presumably to participate in military campaigns. In about 690, was placed as the corps' commander ().