Mieszko I of Poland Denmark, Canute the Great's daughter and wife of Henry III, Holy Roman Emperor. The first Christian ruler of territories later called Poland, Mieszko I is considered the creator of the Polish state. He continued the policy of both his father and grandfather, who were rulers of the pagan tribes located in the area of present-day Greater Poland. Through both alliances and the use of military force, Mieszko extended ongoing Polish conquests and early in his reign subjugated Kuyavia and probably Gdańsk Pomerania and Masovia. For most of his reign, Mieszko I was involved in warfare for the control of Western
Mieszko Kazimierzowic no mention of Mieszko's influence on Polish politics. Mieszko died on 28 January 1065. Year of death was noted by "Rocznik kapituły krakowskiej", while day by "Necrologium monasterii superioris Ratisbonensis". He died unmarried and childless. Mieszko Kazimierzowic Mieszko Kazimierzowic ("Kazimierzowic" means "son of Kazimierz") (16 April 1045 – 28 January 1065) was a Polish prince member of the House of Piast. According to some scholars, he was probably Duke of Kuyavia since 1058 until his death. He was the third son of Casimir I the Restorer by his wife Maria Dobroniega, daughter of Vladimir the Great, Grand Duke of Kiev.