Mieszko I of Poland by him. As Widukind of Corvey wrote, Mieszko ruled over the tribe called the "Licicaviki", now commonly identified with the Polabian Lubusz Land. Having the control over those more western (in respect to the original homeland of the Polans) tribes, Mieszko had entered the German sphere of influence. In 963 the German Margrave Gero conquered territories occupied by the Polabian Lusatian and Słupian tribes, and as a result came into direct contact with the Polish state. At the same time (about 960) Mieszko I began his expansion against the Velunzani and Lutici tribes. The war was recorded by the chronicler
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