duke (from 992) and then (from 1024) first king of Poland, who expanded his country's territory to include Pomerania, Lusatia, and, for a time, the Bohemian princely lands. He made Poland a major European state and also created a Polish church independent of German control.

The son of Mieszko I, the first of the Piast dukes, and the Bohemian princess Dobrawa (Dubravka), Bolesław I inherited the principality of Great Poland (Wielkopolska, between the Oder and the Warta rivers) upon his father's death in 992. He soon began, by energetic political and military action, to develop and expand the Polish state. He conquered Pomerania along the Baltic Sea in 996 and seized Kraków (formerly a Bohemian possession) soon afterward. He ransomed the relics of the martyred St. Adalbert, bishop (Adalbert, Saint) of Prague, from the pagan Prussians and buried the relics at Gniezno. The Holy Roman emperor Otto III, who had been Adalbert's student and Bolesław's ally since 992, attended that ceremony (March 1000) and marked the occasion by personally acknowledging Bolesław as the sovereign ruler of Poland. With Pope Sylvester II's approval, the emperor granted Poland its own archdiocese, with Gniezno as its seat. Bolesław then reorganized Poland's church structure, making it a national church directly under papal jurisdiction and independent of German ecclesiastical control.

After Emperor Otto III's death (1002), Bolesław seized the imperial lands of Lusatia and Misnia (Meissen) and the principality of Bohemia. These actions started a series of three wars between him and the German king Henry II that lasted until 1018, when, by the Treaty of Bautzen, Bolesław retained Lusatia and Misnia and Henry II won Bohemia. Bolesław's expansionist policy continued. When he defeated Grand Prince Yaroslav I the Wise of Kiev in battle (July 21, 1018) and placed his own son-in-law (and Yaroslav's brother), Svyatopolk, on the Kievan throne, his control extended from the western tributaries of the middle Elbe River to the eastern reaches of the Bug River. Though recognized as a sovereign by Otto III in 1000, Bolesław sought to strengthen his position and his independence from imperial control with his papally-sanctioned coronation by the archbishop of Gniezno on Dec. 25, 1024.