The history of Poland during the Piast dynasty is the first major stage in the history of Poland. The Piast period lasted from the late 9th through the 14th century, when Poland was established as a state and a nation during the Middle Ages of European history. The history of the Polish state commences with the founding of the Piast dynasty by Siemowit, succeeded by Lestek and Siemomysl, and finally Mieszko I  around 960, when his rule began. The indigenous Piast ruling house was largely responsible for the formation of the Polish state and remained in power until the second half of the 14th century. Mieszko chose to be baptized in the Western Latin Rite in 966, which established a major cultural boundary in Europe. Mieszko completed the unification of the West Slavic tribal lands fundamental to the existence of the new country of Poland.