High Quality Content by WIKIPEDIA articles! Jacob Svetoslav (Bulgarian: Яков Светослав, Yakov Svetoslav) (ca. 1210s/1220s–1275 or 1276/1277) was a prominent 13th-century Bulgarian noble (bolyarin) of princely Russian origin. Bestowed the title of despot, Yakov Svetoslav was the ruler of a widely autonomous domain of the Second Bulgarian Empire most likely located around Sofia. Seeking further independence and claiming the title of Emperor of Bulgaria, he twice changed allegiance from Bulgaria to the Kingdom of Hungary and vice versa, and the Hungarians recognized his Bulgarian royal rank as their vassal and ruler of Vidin (medieval Bdin).