Mieszko the Younger time in 1166 or 1167 in a document signed between Mieszko III and Casimir II the Just at the congress in Jędrzejów as one of the sons of the Duke of Greater Poland. Between 1177 and 1179, as a result of the revolt against his father, Mieszko, with his parents and siblings, were exiled from Poland. They probably returned to the country in 1181, when Mieszko III regained the rule over Greater Poland. In 1184 and thanks to the wise diplomatic affairs of his father, Mieszko the Younger was appointed by the sickly Duke Leszek Governor of the Masovian-Kuyavian principality,
Mieszko I of Poland in the entry for the year 985 it is noted that Mieszko came to help the Saxons in their fight against some Slavic forces, presumably the Polabians. One year later, the Polish ruler had a personal meeting with the Emperor, an event mentioned in the "Annals of Hersfeld": According to Thietmar and other contemporary chronicles the gift given by Mieszko to the Emperor was a camel. The meeting consolidated the Polish-German alliance, with Mieszko joining Otto's expedition against a Slavic land, which "together they wholly devastated (...) with fire and tremendous depopulation". It is not clear which Slavic territory was