Gunbai fans were used by military leaders in old Japan, and are also used by sumo wrestling empires!! In older Japan, the fan was used to communicate commands to the soldiers. It is also used in sumo wrestling, so the empire can point the gunbai to the victor of the bout! Gunbai is usually made of solid wood, wood covered with metal, or sometimes completely solid metal.
This saying 'furinkazan' also translated to 'Wind, forest, fire, mountain' was popularly used by the shogen Takeda Shingen!