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 II the Fat which was given to their mother Viola as her . Mieszko II the Fat Mieszko II the Fat () ( – 22 October 1246) was a Duke of Opole-Racibórz from 1230 until his death, and Duke of Kalisz-Wieluń during 1234–1239 (with his brother as co-ruler). He was the eldest son of Duke Casimir I of Opole by his wife Viola, probably a Bulgarian lady. At the time of his father's death in 1230, Mieszko II and his younger brother Władysław were still minors; for this, the regency of the Duchy was taken by their mother and Henry I the Bearded,