Mieszko II Lambert of Pöhlde asked the Emperor to defend against the attacks of Mieszko II, promising support in the fight against the Polish ruler. Despite the treaty which secured peace between Poland and Germany, the Emperor soon armed a retaliatory expedition against Mieszko II. Conrad II's army arrived to Lusatia in the autumn of 1029 and began the siege of Bautzen; but the German troops did not receive the promised support of the Lutici tribe and the expedition failed. Threatened by the Hungarians, the Emperor was forced to retreat. Probably in this same year the son of Oldřich, Bretislaus I, attacked and
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