Casimir IV of Poland, born in 1427, was a significant monarch who ruled from 1447 until his death in 1492. He was a member of the Jagiellonian dynasty and is known for strengthening the Polish-Lithuanian union. His reign marked a period of territorial expansion and economic growth, particularly through the consolidation of power in Prussia. Under Casimir IV's leadership, Poland became a major player in European politics. He successfully defended the kingdom against external threats, including the Teutonic Knights, and fostered cultural development. His efforts laid the groundwork for the future prosperity of the Polish-Lithuanian Commonwealth.