Murad II, 1403–51, Ottoman sultan (1421–51), son and successor of Muhammad I to the throne of the Ottoman Empire (Turkey). He was opposed at his accession by a pretender, Mustafa, who rapidly gained control over most of the Ottoman possessions in Europe. After defeating his rival, Murad unsuccessfully laid siege (1422) to Constantinople. In a war with Venice he seized (1430) Salonica, thus proving Ottoman naval power, and invaded Greece. In the north Murad fought the resistance led by John Hunyadi. Murad sought to retire from public life on several occasions, but each time was recalled by the pressure of events. In 1444 he won the great victory of Varna against the crusading forces led by King Ladislaus III of Poland and Hungary. Murad was a patron of poetry and learning, and his court was a cultural center. His son Muhammad II succeeded him.