Count John III was a notable figure in the history of Lithuania and Poland. He served as the Grand Duke of Lithuania from 1530 until his death in 1548. His reign was marked by efforts to strengthen the central authority of the state and to promote the Union of Lublin, which united the Grand Duchy of Lithuania and the Kingdom of Poland. John III was also known for his diplomatic skills, particularly in managing relations with neighboring countries. He worked to maintain peace and stability in the region, navigating complex political landscapes while fostering alliances that would benefit both Lithuania and Poland.