Casimir IV, 1427–92, king of Poland (1447–92). He became (1440) ruler of Lithuania and in 1447 succeeded his brother Ladislaus III as king of Poland. He united the two nations more closely by placing them on an equal footing. With the Second Peace of Torun (1466) he ended a 13-year war against the Teutonic Knights in his favor; Poland gained territories and the Knights accepted Polish suzerainty over the area they retained. Calling (1467) the first Polish diet, he confirmed the privileges of the aristocracy. His marriage to an Austrian Hapsburg enabled his son Ladislaus to become king of Bohemia and later king of Hungary as Uladislaus II. Casimir was succeeded by his sons John I (1492–1501), Alexander I (1501–5), and Sigismund I (1506–48).