In the late ninth century, a man crossed a mountain frontier with a Bulgarian army at his back, seized the fortified capital of a principality he had never governed, and died in the fighting when the defending prince came to retake it. Prince Klonimir Strojimirovic's campaign lasted weeks. Its consequences lasted a century.The House of Vlastimirovic ruled the early medieval Serbian principality for a hundred years of extraordinary violence and political ingenuity - a dynasty torn apart by the structural logic of its own succession system, sustained by Bulgarian patronage and Byzantine recognition, and ultimately restored, in its greatest territorial achievement, by a prince formed at the intersection of two civilizations. This is the story of how a dynastic feud became a theatre of geopolitical competition, how two great empires invested in the bloodlines of displaced Serbian princes as instruments of long-range foreign policy, and how the failure of one man's military campaign created the conditions under which his son could succeed where he had not.Drawing on De Administrando Imperio, the Byzantine imperial manual that remains our primary source, and on the archaeological evidence of the Golden Seal of Prince Strojimir - fifteen grams of ninth-century gold bearing a Greek prayer - this book reconstructs a forgotten world of mountain fortresses, court exiles, and dynastic calculations whose logic was as precise as it was letha