Khan Kardam was the ruler of Bulgaria from 777 to 802, known most for his establishment of order in Bulgaria and his defeat of attacking Byzantine forces. Kardam usurped the throne amidst chaotic infighting of nobles. His line was unbroken until the death of Roman I of Bulgaria in 997.
Because the Byzantine Empire was weak during this period, Kardam was able to expand to the south and southwest, where he found potential allies in the native Slavic tribes.
In 789 Kardam defeated the Byzantines at Struma river. The Strimonians welcomed the Bulgarians. Emperor Constantine VI attacked Kardam in July, 796 near Marcellae in Thrace, where he was defeated; the Byzantine leaders were killed and most of their supplies plundered, according to Theophanes.
Bulgaria's honor was restored, and Constantine returned to Constantinople, after signing a peace treaty to pay tribute to the Bulgarians. The emperor attempted to weasel out of the tribute; in response, Kardam replied "Pay your dues or I'll ravage Thrace."
Kardam spent the remainder of his years in peace, confident that he had united the state and secured the power of the Kahn.