Boleslaus I, Duke of Bohemia

Boleslaus I, a member of the Přemyslid dynasty, was ruler of the Duchy of Bohemia from 935 until his death in 972. He is notorious for the murder of his elder brother Wenceslaus I, through which he became duke. As duke, his decisions surrounding his dynasty led to the Roman Catholic conversion of Poland, which in turn led to the recognition of the Polish state by the papacy. This recognition helped to define medieval Poland as one of the first modern states.