Casimir I the Restorer not supported by modern historians. Regardless, he left church work for good in 1031. Casimir's father, Mieszko II, was crowned King of Poland in 1025 after the death of his father Bolesław I the Brave. However, the powerful magnates of the country feared a strong central government like the one that existed under Bolesław I's rule. This led to considerable friction between the King and the nobility. Taking advantage of the King's precarious situation, Mieszko II's older half-brother Bezprym and younger brother Otto turned against him and allied themselves with the Holy Roman Emperor Conrad II, whose forces attacked Poland
Mieszko I, Duke of Cieszyn shelter to the Bishop in Raciborz. His politics against Henry IV were reinforced when the Duke of Wrocław repudiated his wife Constance —sister of Mieszko— and sent her back to her homeland. Another consequence of Mieszko's politics was an armed expedition of Henry IV in 1287 against Racibórz, who was sieged. Then Mieszko was forced to refuse his help to the Bishop. In 1290 the division was made of the Duchy of Racibórz: Przemysław retained Racibórz and Mieszko obtained the rule over the districts of Cieszyn, Oświęcim and Zator. The first time that he signed himself as Duke of Cieszyn