Murad II was the Ottoman Sultan from 1421 to 1444 and again from 1446 to 1451. He was the son of Mehmed I and played a crucial role in consolidating the Ottoman Empire during his reign. Murad II faced numerous challenges, including internal revolts and external threats from the Crusaders and the Byzantine Empire. During his rule, Murad II expanded the empire's territory, particularly in the Balkans. He is known for his military campaigns, including the successful siege of Varna in 1444. His reign laid the groundwork for the future expansion of the Ottoman Empire under his son, Mehmed II.