What is "isbul"

Isbul ( fl. 820s–830s) was the kavhan, or first minister, of the First Bulgarian Empire during the reigns of Omurtag, Malamir and Presian I. Appointed to the kavhan office under Omurtag, Isbul was a regent or co-ruler of the underage Malamir and his successor Presian.

Under Malamir and Presian, Isbul headed Bulgaria's successful campaigns against the Byzantines in southern Thrace and Macedonia, which led to a significant territorial expansion of the Bulgarian realm. As a co-ruler of Malamir, Isbul also financed the construction of a water conduit in the capital Pliska. As second-in-command, Isbul held enormous power and wealth, and was unusually often mentioned beside the name of the ruler in inscriptions. Due to his merits, Isbul has been described as an architect of medieval Bulgarian statehood by historians.