Jan II Casimir Vasa, b 22 March 1609 in Cracow, d 16 December 1672 in Nevers, France. (Portrait: Jan II Casimir Vasa.) King of Poland and grand duke of Lithuania in 1648–68; the son of Sigismund III Vasa. The last ruler of the Vasa dynasty to occupy the Polish and Lithuanian thrones, Jan was elected king after the death of his brother Wladyslaw IV Vasa.
During his reign the Polish magnates pressed him to expend Poland's resources on winning the Cossack-Polish War of 1648–57. In 1649 and 1651, he personally directed military campaigns against Hetman Bohdan Khmelnytsky and the Cossacks in Ukraine. After the Pereiaslav Treaty of 1654 placed Ukraine under Muscovite protection, he was forced into a long war with Muscovy (1654–67). This further exhausted Poland, as did internal discord and the war with Sweden and its allies (1655–60).
Jan concluded the Treaty of Hadiache with Hetman Ivan Vyhovsky in 1658 and the Treaty of Andrusovo with Muscovy in 1667. His attempts at strengthening royal absolutism caused a mutiny among the gentry, who forced him to abdicate in 1668 and to go to France.
