At the death of Stephen (Lazarević), in 1427, he was succeeded as _Despot_ by his nephew, George Branković; but the Sultan, claiming Serbia as his own, immediately declared war on him. The Serbian ruler had to abandon Belgrade to the Magyars, and Nish and Kruševac to the Turks. He then built and fortified the town of Smederevo (or Semendria) lower down on the Danube, in 1428, and made this his capital. He gave his daughter in marriage to the Sultan, but in spite of this war soon broke out again, and in 1441 the Turks were masters of nearly the whole of Serbia. Later George Branković made another alliance with Hungary, and in 1444, with the help of John Hunyadi, defeated the Turks and liberated the whole of Serbia as far as the Adriatic, though he remained a tributary of the Sultan. The same year, however, the Magyars broke the treaty of peace just concluded with the Turks, and marched against them under their Polish king, Ladislas; this ended in the disastrous battle of Varna, on the Black Sea, where the king lost his life. In 1451 Sultan Murad II died and was succeeded by the Sultan Mohammed. In 1453 this sultan captured Constantinople (Adrianople had until then been the Turkish capital); in 1456 his armies were besieging Belgrade, but were defeated by John Hunyadi, who, unfortunately for the Serbs, died of the plague shortly afterwards. George Branković died the same year, and at his death general disorder spread over the country. The Turks profited by this, overran the whole of Serbia, and in 1459 captured Smederevo, the last Serbian stronghold.