from a godless tyrant (i.e. Matthias Corvinus) and marauding pagans (i.e. Muslim Ottoman Turks). Prince Casimir was also exposed to the cult of his uncle King Władysław III of Poland who died in the 1444 Battle of Varna against the Ottomans. This led some researchers, including Jacob Caro, to conclude that the Hungarian campaign pushed Prince Casimir into religious life. Later life and death As his elder brother, Vladislaus II, ruled Bohemia, Prince Casimir became the heir apparent to the throne of Poland and Lithuania. Italian humanist writer Filippo Buonaccorsi (also known as Filip Callimachus) was hired to become Casimir's tutor in political matters, but his Renaissance views had less influence on Casimir than Długosz. In 1474, the Italian merchant and traveler Ambrogio Contarini met with Prince Casimir and was impressed by his wisdom. Prince Casimir completed his formal education at age 16 and spent most of his time with his father. In 1476, Prince Casimir accompanied his father to Royal Prussia where he tried to resolve the conflict with the Prince-Bishopric of Warmia (see War of the Priests). In 1478 Seimas of the Grand Duchy of Lithuania demanded that King Casimir IV leave either Prince Casimir or Prince John I Albert in Lithuania as a regent. King Casimir IV feared separatist moods and refused, but after settling the conflict in Prussia, moved to Vilnius. Between 1479 and 1484 his father spent most of his time in Vilnius attending to the affairs of Lithuania. In 1481, Mikhailo Olelkovich and his relatives planned to murder King Casimir and Prince Casimir during a hunt at a wedding of Feodor Ivanovich Belsky. The plan was discovered and Prince Casimir, perhaps fearing for his safety, was sent to Poland to act as vice-regent. Around the same time his father tried to arrange his marriage to Kunigunde of Austria, daughter of Emperor Frederick III. It is often claimed that Prince Casimir refused the match, preferring to remain celibate and sensing his approaching death. According to Maciej Miechowita, Prince Casimir developed tuberculosis. In May 1483, Prince Casimir joined his father in Vilnius. There, after the death of Andrzej Oporowski, Bishop and Vice-Chancellor of the Crown, Prince Casimir took over some of his duties in the chancellery. However, his health deteriorated while rumors about his piousness and good deeds spread further. In February 1484, the Polish sejm in Lublin was aborted as King Casimir IV rushed back