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 socially connected primarily by tribal structures. It appears that the elders cooperating with the Duke first felt the need for super-tribal unity, as expansion allowed them to broaden their influence. Mieszko and his people were described around 966 by Abraham ben Jacob, a Sephardi Jewish traveller, who at that time visited the Prague court of Duke Boleslav I the Cruel. Abraham presented Mieszko I as one of the four Slavic "kings", reigning over a vast "northern" area, with a highly regarded and substantial military force at his disposal. More precise contemporary records regarding Mieszko were compiled by Widukind of Corvey,