Mieszko II Lambert Gniezno Cathedral. Contemporary German chroniclers considered this to be an abuse of power on the part of the Archbishop, which was made necessary by the existing political situation. After his father's death, Mieszko inherited a vast territory, which in addition to Greater Poland, Lesser Poland, Silesia and Gdansk Pomerania also included Western Pomerania, as well as Lusatia, Red Ruthenia and territory of present-day Slovakia. Whether Moravia was still under his reign or was lost earlier is disputed. Once his solo reign had begun, as an important Central European ruler, he was now very important to the Holy Roman Empire. Later
Mieszko Kazimierzowic "Gesta principum Polonorum" written in the early 12th century, put Mieszko third in order, among his brother. Modern historian, Janusz Bieniak, has supposed that Mieszko was the second son of Casimir I and was older than Władysław Herman, but most scholars disagree with this hypothesis. The date of Mieszko's birth was given by "Rocznik krakowski" (Kraków Annals). This source omitted dates of birth of Mieszko's brothers. Kazimierz Jasiński thought that "Rocznik" was started shortly before Mieszko's birth and this was the reason for absence of his older brothers. Przemysław Wiszewski supposed tha Casimir I chose Mieszko as his successor and