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 Tanglefoot Casimir II's eldest son, Leszek the White. Both sides clashed in the bloody Battle of Mozgawa (Mozgawą) near Jędrzejów (13 September 1195), where Mieszko III was seriously injured and his son Bolesław of Kuyavia died. The Silesian troops, led by Mieszko and Jarosław, arrived to the battlefield too late, soon after Mieszko III withdrew to Kalisz. Despite the forces of the Count palatine Goworek who also arrived to help Leszek's troops, the Silesians obtained a great victory; however, because Mieszko III wasn't present, this victory brought to them only benefits in terms of prestige (not counting the ransoms obtained by