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 I of Poland situation at that time. Another debatable point is Thietmar's claim that Mieszko "subordinated himself to the King". Most historians believe that it was only a matter of recognition of Otto's royal authority. Some suggest that a fealty relationship could in fact be involved. Whether or not the German-Polish invasion of Bohemia actually happened, the friendly relations between the Czechs and the Poles came to an end. Bohemia resumed its earlier alliance with the Lutici, which caused in 990 a war with Mieszko, who was supported by Empress Theophanu. Duke Boleslav II was probably the first one to attack. As a