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Casimir IV,1427–92, king of Poland (1447–92). He became (1440) ruler of Lithuania and in 1447 succeeded his brother Ladislaus IIILadislaus III,
1424–44, king of Poland (1434–44) and, as Uladislaus I, king of Hungary (1440–44), son of Ladislaus II. He led two crusades against the Ottomans; the first (1443) was highly successful, but the second ended with his defeat and death in the battle
..... Click the link for more information. 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 KnightsTeutonic Knights
or Teutonic Order
, German military religious order founded (1190–91) during the siege of Acre in the Third Crusade. It was originally known as the Order of the Knights of the Hospital of St. Mary of the Teutons in Jerusalem.
..... Click the link for more information. 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).