The Counts of Walbeck ruled a medieval territory with its capital Walbeck northeast of Helmstedt in the present town Oebisfelde-Weferlingen in Saxony-Anhalt. The foundation of the Archbishopric of Magdeburg established the region as firmly in the oversight of Otto the Great, Holy Roman Emperor. The first Count of Walbeck, Lothar I, was great-grandfather of Thietmar, Prince-Bishop of Merseburg, chronicler of the Ottonian dynasty of Germany and the Holy Roman Empire. Two of Thietmar’s great-grandfathers, both named Lothar, were killed in the Battle of Lenzen, pitting the forces of Henry the Fowler against the Slavs. The early Margraves of the Nordmark were descended from the House of Walbeck.