Were trained for espionage and assassination. They probably date back from the Heian period (794-1185) in Kyoto, where they mingled with the yamabushi. They usually came from the lower castes and were used by the Daimyo (clanleaders) to murder enemies or to spy in enemy castles. The ninja were particularly active at the beginning of the 15th century. As acrobatic master they could easily scale walls and swim without making a sound. The myth of invisibility came from their expertise in disguising and hiding. Their special weapons, outfit and clothes was to that same purpose of secrecy. Anything was allowed to reach their aim. Their skills included the use of all weapons, their knowledge included chemistry and poison. In their hierarchy stands the leader or Jonin above his lieutenants or Chunin. The lowest order or Genin carried out the assignments.
During the peaceful Edo-period they started to form organized crime. No wonder that when the stories about these 'miracle men' reached the West, their popularity rose equal to that of Karate and Kung-fu.
The modern approach of Ninjutsu shifts the focus from those deadly techniques towards a mixture of philosophy, unarmed combat, swordfighting and all kinds of survival-techniques.
The succes caused a lot of commercial fraud in the 80s with fake schools and trainers. This in turn led towards the present decline in popularity.

A farming implement from Okinawa used to beat rice straw. These two pieces of wood connected by a double cord or chain became a formidable weapon in occupied Okinawa where the possession of weapons was forbidden. The Bruce Lee films popularized the weapon in the West to such an extent that in many countries this weapon has been made illegal. The handles are usually between 26 and 35cm long, but shorter or longer versions exist.