Casimir I the Restorer

Casimir I the Restorer (Polish: Kazimierz I Odnowiciel; 25 July 1016 – 19 March 1058), a member of the Piast dynasty, was the duke of Poland from 1040 until his death. Casimir was the son of Mieszko II Lambert and Richeza of Lotharingia. He is known as the Restorer because he managed to reunite parts of the Kingdom of Poland after a period of turmoil. He reintegrated Masovia, Silesia and Pomerania. However, he failed to crown himself King of Poland, mainly because of internal and external threats to his rule.

Source: Wikipedia — https://en.wikipedia.org/wiki/Casimir_I_the_Restorer