Zbigniew Oleśnicki ( cardinal ) Zbigniew Oleśnicki or Zbigniew z Oleśnicy ( 5 December 1389 in Sienno , Masovian Voivodeship – 1 April 1455 ) , known in Latin as Sbigneus , was a high - ranking Roman Catholic clergyman and an influential Polish statesman and diplomat . He served as Bishop of Kraków from 1423 until his death in 1455 . He took part in the management of the country ' s most important affairs , initially as a royal secretary under King Władysław II Jagiełło and later as the effective regent during King Władysław III ' s minority . In 1449 he became the first native Polish cardinal . At the age of twenty he was secretary to King Władysław Jagiełło , and fought with him in the battle of Grunwald on 14 July 1410 . A favourite with the king , he took part in the management of the country ' s most important affairs . His influence with the king greatly aided him in opposing the Hussites , who had gained royal favour . On 9 July 1423 , he was appointed to the episcopal See of Kraków , and in 1433 he was sent by the king as legate to the council of Basle , where he endeavoured to be on friendly terms with both parties . On 18 December 1439 , he was created cardinal priest with the titular church of St . Prisca , by Pope Eugene IV . As cardinal , his influence in Poland was second only to that of the king , and , during the frequent absence of Casimir IV in Lithuania , he transacted the affairs of the State . He was recognized as one of the two most important Polish magnates of his time ( the other one was magnate Jan Tęczyński . In 1449 , after the death of archbishop of Gniezno and primate of Poland Wincenty Kot , the position was proposed to Oleśnicki , but he refused it . It then passed to his political rival , bishop Władysław Oporowski . In his conduct of Poland ' s affairs Oleśnicki entertained far - reaching imperial dreams , which included a complete assimilation of Lithuania into the Polish state and the conquest of Silesia from the Kingdom of Bohemia . In particular , Oleśnicki pursued the idea of a Crusading alliance with Hungary against the Ottoman Turks , with the ultimate aim of extending Poland ' s boundaries to the Black Sea . This was manifested in promoting Władysław III ' s taking the Hungarian Crown - to which some Polish magnates were strongly opposed . However , all these aspirations came to naught with King Władysław ' s death at the Battle of Varna . Being a man of great learning , he advanced the study of arts and letters in every possible way , and the flourishing condition of the University of Krakow during his episcopacy is due chiefly to his efforts . The well - known historian Jan Długosz was his secretary . To repress the spread of Hussitism he called Giovanni da Capistrano ( then in Breslau ) and the Minorites to Kraków . Da Capistrano , whom Oleśnicki invited , was also known for his anti - Jewish zeal , in which he engaged in Poland as in other countries . Oleśnicki ' s own Anti - Jewish intolerance was manifested in his strongly criticising Casimir IV for reaffirming in 1453 the tolerant measures towards Jews enacted by Casimir III . Under Oleśnicki ' s influence , the 1454 Statutes of Nieszawa included the provisions that Jews ' rights be " restricted when they contradict canon law " and that Polish Jews be compelled to wear distinctive clothing . However , this was never enforced in practice .