Casimir IV KG (Polish: Kazimierz IV Andrzej Jagiellończyk) 30 November 1427 – 7 June 1492) of the Jagiellonian dynasty was Grand Duke of Lithuania from 1440 and King of Poland from 1447, until his death. He was one of the most active Polish rulers, under whom Poland, by defeating the Teutonic Knights in the Thirteen Years' War recovered Pomerania, and the Jagiellonian dynasty became one of the leading royal houses in Europe. He was a strong opponent of aristocracy, and helped to strengthen the importance of Parliament and the Senate.