Muhammad IV or Mehmet IV, 1641–92, Ottoman sultan (1648–87). He was proclaimed sultan of the Ottoman Empire (Turkey) by the corps of Janissaries after the deposition and murder of his father, Sultan Ibrahim. Disorder and corruption continued until the Köprülü family obtained (1656) the office of grand vizier (chief executive officer) and restored order. However, the empire suffered severe setbacks. Algiers freed itself (1669) from Ottoman suzerainty. In 1683 the Turks, in alliance with the Hungarian Thököly, besieged Vienna but were repulsed by King John III of Poland. Turkish weakness being apparent, a Holy League was formed to carry the war into Ottoman territory. After the Turkish defeat (1687) at Mohacs by Charles V of Lorraine, Muhammad was deposed. His brother, Sulayman II, succeeded him.
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