WARSAW, Poland (AP) — Poland's president is leading formal celebrations marking the 1,050th anniversary of Christianity in Poland with a speech declaring the baptism of Poland's first king as the most important historical event in the nation's history.

President Andrzej Duda spoke Friday on the second of three days of fanfare marking the baptism in 966 of Mieszko I, Poland's first king. The event marks the birth of Polish statehood as well as the start of a centuries-long process of Christianization of formerly pagan tribes on Polish lands.

Duda, speaking to a joint gathering of both houses of parliament and bishops in the city of Poznan, says the baptism was a breakthrough for the nation because it brought it into the sphere of Western European civilization.