Ferdinand II, Holy Roman Emperor, ruled from 1619 to 1637 and was a key figure during the early stages of the Thirty Years' War. He was a member of the House of Habsburg and was known for his strong Catholic faith, which influenced his policies and actions throughout his reign. Ferdinand sought to consolidate his power and strengthen Catholicism in the empire, often leading to conflicts with Protestant states. His reign was marked by significant military and political challenges, including the rise of Protestantism and various uprisings. Ferdinand II's efforts to maintain control over the empire contributed to the prolonged and devastating nature of the Thirty Years' War, which had lasting effects on Europe.