MURAD II  . (1403–1451) succeeded his father Mahommed I. in 1421 . The attempt of his uncle Prince Mustafa to usurp the throne, supported as it was by the Greeks, gave trouble at the outset of his reign, and led to the unsuccessful siege of Constantinople in 1422 . Murad maintained a long struggle against the Bosnians and Hungarians, in the course cf which Turkey sustained many severe reverses through the valour of Janos Hunyadi . Accordingly in 1444 he concluded a treaty at Szegedin for ten years, by which he renounced all claim to Servia and recognized George Brancovich as its king . Shortly after this, being deeply affected by the death of his eldest son Prince Ala-ud-din, he abdicated in favour of Mahommed; his second son, then fourteen years of age . But the treacherous attack, in violation of treaty, by the Christian powers, imposing too hard a task on the inexperienced young sovereign, Murad returned from his retirement at Magnesia, crushed his faithless enemies at the battle of Varna (Novemebr to, 1444), and again withdrew to Magnesia . A revolt of the janissaries induced him to return to power, and he spent the remaining six years of his life in warfare in Europe, defeating Hunyadi at Kossovo (October 17–19, 1448) . He died at Adrianople in 1451, and was buried at Brusa . By some considered as a fanatical devotee, and by others as given up to mysticism, he is generally described as kind and gentle in disposition, and devoted to the interests of his country .