Casimir IV Jagiellończyk, (Kazimierz) b 30 November 1427 in Cracow, d 7 June 1492. Son of Jagiełło and his fourth wife, the Ukrainian princess Sofiia Holshanska. Casimir became grand duke of Lithuania in 1440 and king of Poland in 1447. He adopted a centralist policy with regard to the Ukrainian lands and favored the Lithuanian Catholic nobles in the Grand Duchy of Lithuania. He abolished the principality of Volhynia in 1452 and the Kyiv principality in 1470. In 1481 he uncovered a conspiracy of the Ukrainian princes led by Mykhailo Olelkovych and executed them. Other princes transferred their allegiance and their lands to Muscovy. During Casimir's reign the Crimean Tatars, now vassals of the Ottoman Empire, resumed their incursions, destroying Kyiv in 1482. The major development in church affairs during Casimir's reign was the definitive separation of the Moscow metropoly from that of Kyiv metropoly. Casimir was succeeded by his son Alexander Jagiellończyk.
Encyclopedia of Ukraine