Mieszko I of Poland elders, and limited their authority. Clergy who arrived in the country contributed to the development of education and culture, and of the state administration and diplomacy, as well. At the end of Mieszko's reign (ca. 990), Poland began to pay tribute to the pope (Peter's Pence). However, the conversion of the Polish population to Catholicism was a long-term process, and was not completed during the reign of Mieszko I. The duke probably had to deal with rebellions led by the old pagan priest caste. In some villages, the old Slavic beliefs and customs were continued until the 16th century. After
Mieszko III the Old of the rebels and divided Henry's Duchy in three parts: Wiślica Land was taken by Casimir, Bolesław took Sandomierz proper, and the rest was led to Mieszko. In 1172 another conflict arose among the Silesian Piasts, when Duke Bolesław the Tall chose to ignore the claims of his first-born son, Jaroslaw by designating his son of the second marriage Henry I the Bearded his sole heir. When Jarosław, forced to become a priest, had returned from his German exile, he claimed a share of the Silesian lands. Mieszko III supported his grandnephew in his demands, and the civil war was