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Boleslaus III,1085–1138, duke of Poland (1102–38). The kingdom had been divided by his father, Ladislaus Herman, between Boleslaus and his elder brother Zbigniew, whose legitimacy was disputed. Zbigniew was supported by the Holy Roman emperor and other powers; however, Boleslaus defeated Zbigniew and reunited the kingdom. He routed (1109) Holy Roman Emperor Henry V at Hundsfeld and warred against Bohemia, Hungary, and Kiev. Having also regained Pomerania, which Mieszko II had lost to Denmark, Boleslaus entrusted the Christianization of its inhabitants to the bishop of Bamberg. In 1135 at Merseburg he signed a treaty with Holy Roman Emperor Lothair II, by which he received Pomerania and Rügen as fiefs of the empire. Vainly seeking to prevent the disintegration of his kingdom, Boleslaus altered the law of succession of his dynasty (see PiastPiast
, 1st dynasty of Polish dukes and kings. Its name was derived from that of its legendary ancestor, a simple peasant. The first historic member, Duke Mieszko I (reigned 962–92), began the unification of Poland and introduced Christianity.
..... Click the link for more information. ). Among his sons, Casimir IICasimir II,
1138–94, duke of Poland (1177–94), youngest son of Boleslaus III. A member of the Piast dynasty, he drove his brother Mieszko III from power at Kraków in 1177 and became the principal duke of Poland.
..... Click the link for more information. was the most notable.