The Ottoman army advanced as far as Belgrade, where it attempted but failed to conquer the city from John Hunyadi at the Siege of Belgrade, on 14 July 1456. A period of relative peace ensued in the region until the Fall of Belgrade in 1521, during the reign of Mehmed's great-grandson, known as Sultan Suleiman the Magnificent. The sultan retreated to Edirne, and Đurađ Branković regained possession of some parts of Serbia. Before the end of the year, however, the 79-year-old Branković died. Serbian independence survived him for only two years, when the Ottoman Empire formally annexed his lands following dissension among his widow and three remaining sons. Lazar, the youngest, poisoned his mother and exiled his brothers, but he died soon afterwards. In the continuing turmoil the oldest brother Stefan Branković gained the throne but was ousted in March 1459. After that the Serbian throne was offered to Stephen Tomašević, the future king of Bosnia, which infuriated Sultan Mehmed. He sent his army, which captured Smederevo in June 1459, ending the existence of the Serbian Despotate.