Boleslaus I (bō´ləslôs), c.966–1025, Polish ruler (992–1025), the first to call himself king; also called Boleslaus the Brave. He succeeded his father, Mieszko I, as duke of Poland, seized the territories left to his two brothers under their father's will, and set about increasing his holdings. With the sanction of Holy Roman Emperor Otto III, he obtained (1000) the elevation of Gniezno into a metropolitan see, thus emancipating the Polish church from German control. Otto also supported plans for Polish political autonomy. Otto's successor, Holy Roman Emperor Henry II, opposed Boleslaus's ambition; when Boleslaus overran Meissen and the East Mark, Henry refused to confirm his control of these territories. Boleslaus took advantage of dynastic troubles to occupy Bohemia in 1003; expelled in 1004, he still retained Moravia. He repelled a series of invasions of Poland by Henry. In 1018, in the Peace of Bautzen, Boleslaus received Lusatia as a fief of the Holy Roman Empire. Subsequently he campaigned successfully against Kiev. Boleslaus ranks among Poland's foremost rulers; he reorganized the administration, systematized taxation, and created a large standing army. Shortly before his death he was crowned king with the approval of the Holy See. He was succeeded by his son, Mieszko II.