Kazimierz IV Jagiellończyk, also known as Casimir IV of Poland, was a significant monarch who ruled from 1447 to 1492. He was a member of the Jagiellonian dynasty and is best known for strengthening the Kingdom of Poland and the Grand Duchy of Lithuania through his reign. His leadership helped to consolidate power and expand the territories of both states. During his rule, Kazimierz IV focused on economic development and military reforms, which contributed to the prosperity of his realm. He also played a crucial role in the Thirteen Years' War against the Teutonic Knights, leading to the eventual victory and the signing of the Second Peace of Thorn in 1466.