Mieszko II Lambert by the chronicles of Gottfried of Viterbo, refers to Bezprym. However, the historians now think that he was killed in a plot hatched by the aristocracy. He was buried in the Cathedral of St. Peter and St. Paul. After Mieszko II's death, Poland's peasants revolted in a "pagan reaction." The exact reasons and date are unknown. Mieszko II's only son and heir, Casimir I, was either expelled by this insurrection, or the insurrection was caused by the aristocracy's expulsion of him. Some modern historians argue that the insurrection was caused more by economic than by religious issues, such as new
Mieszko I of Poland probably closer to the latter date. Due to the lack of sources it is not possible to determine exactly which lands he inherited. Certainly among them were the areas inhabited by the Polans and Goplans, as well as the Sieradz-Łęczyca lands and Kuyavia. It is possible that this state included also Masovia and Gdańsk Pomerania. Soon the new ruler had faced the task of integrating the relatively large, ethnically and culturally heterogeneous territory. Although the residents of areas controlled by Mieszko spoke mostly one language, had similar beliefs and reached a similar level of economic and general development, they were