Henry IV Probus was a Polish king who ruled from 1384 to 1399. He was a member of the Piast dynasty and is known for his efforts to strengthen the Polish state and promote its independence. His reign was marked by conflicts with the Teutonic Knights and efforts to consolidate power within the kingdom. During his rule, Henry IV Probus focused on economic development and the establishment of law and order. He also worked to improve relations with neighboring countries, which helped to stabilize the region. His leadership laid the groundwork for future Polish rulers and the eventual rise of the Polish-Lithuanian Commonwealth.