Ottoman sultan (1421-1444 and 1446-1451).
On his accession to the throne following the death of his father, Mehmed I (1421), Murad II faced two challenges to his leadership: one from his uncle Düzme Mustafa, and the other from his own brother Mustafa. Having successfully defeated both rivals, Murad set about securing his position, campaigning against the rival Turkish state of Karaman, based round Konya, and dealing with his enemies in Europe, in particular the very able John Hunyadi, voivod of Transylvania. After an unsuccessful siege of Constantinople (mod. Istanbul, Turkey), Murad concluded a treaty in 1424 with the Byzantines.
By the 1440s, Murad, a gentle, humane, and liberal man according to the Genoese merchant Jacopo di Promontorio, appears to have tired of ruling, and, possibly due to the death of his son Alaeddin, abdicated in 1444, leaving the throne to his son Mehmed II. Before doing so, he arranged the Treaty of Adrianople (mod. Edirne, Turkey) with Hungary and Serbia in 1444 and a treaty with Karaman, also in 1444, in an attempt to ensure peaceful relations with his neighbors. Peace was, however, not achieved; on the accession of the young and inexperienced Mehmed II, John Hunyadi and King Vladislav I of Hungary promptly attacked. Murad returned from retirement to lead the Ottoman army. At the battle of Varna (1444), the Ottomans defeated the Hungarians; Vladislav was killed, and Hunyadi fled. For the next two years, Mehmed continued precariously on the throne, but was brought down by a Janissary revolt in 1446. Brought back to the throne, Murad II reestablished Ottoman control firmly over the European territories, defeating Hunyadi at the second battle of Kosovo in 1448. He was less successful against George Kastrioti, known as Skanderbeg, who battled against the Ottomans in Albania. Murad II died in 1451 and was succeeded for the second time by his son Mehmed II.