Mehmed IV came to the throne at the age of six after his father was overthrown in a coup. Mehmed went on to become the second-longest-reigning sultan in Ottoman history after Suleiman the Magnificent. While the initial and final years of his reign were characterized by military defeat and political instability, during his middle years he oversaw the revival of the empire's fortunes associated with the Köprülü era. Mehmed IV was known by contemporaries as a particularly pious ruler, and was referred to as gazi, or "holy warrior" for his role in the many conquests carried out during his long reign. Under Mehmed IV's reign, the empire reached the height of its territorial expansion in Europe.