Mieszko III the Old attention of Emperor Frederick Barbarossa, who offered his help in his restoration on the Polish throne after a payment of 10,000 pieces of silver, a sum that Mieszko couldn't reunited. Finally in Pomerania, his other son-in-law Duke Bogislaw I accepted to help him. By the agency of his Pomeranian allies, Mieszko forged his links with their Polish followers, grouped around Zdzisław, Archbishop of Gniezno and in 1181 was able to conquer the eastern Greater Polish lands of Gniezno and Kalisz, which until then had been part of the Seniorate Province. Soon after, Mieszko also managed to recover western Greater Poland.
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