Per the long-standing, but now controversial, Ottoman decline thesis (see below), the empire reached its apex under Suleiman the Magnificent in the 16th century when it stretched from the Persian Gulf in the east to Algeria in the west, and from Yemen in the south to Hungary and parts of Ukraine in the north. According to this thesis, Suleiman's reign was the zenith of the Ottoman classical period, during which Ottoman culture, arts, and political influence flourished, although the empire would not reach its maximum territorial extent until 1683, on the eve of the Battle of Vienna.