Casimir I the Restorer
Casimir I the Restorer (; 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 reconquer those provinces which his predecessors had expanded into but were ultimately expelled from. In 1047, with the assistance of the Russians, he conquered independent Masovia, and defeated the Pomeranians who had come to the aid of Marsovia. He temporarily drove the Bohemians from Silesia also. However, he failed to crown himself King of Poland, mainly because of internal and external threats to his rule.