The Piast clan dominated their neighboring Slavic, pagan tribal groups around the 6th century, established the first recognizably Polish state by the 10th century, and ultimately founded a Polish kingdom, which the dynasty ruled for four centuries. In 965, Piast clan leader Mieszko formed a strategic alliance with Bohemia’s Duke Bolesław I the Cruel by marrying the duke’s daughter, Dobrawa. Mieszko’s conversion to Christianity on April 14, 966, known as the Baptism of Poland, is traditionally considered to be the nation’s founding event.