Ninja or Shinobi (literally, "One who is concealed, or one that endures") were sometimes assassins and agents of espionage. Ninja, like samurai, followed their own special code of conduct, called ninpō. Some modern practitioners of budo ninjutsu argue that ninja were hardly ever used as assassins, but rather for espionage. Ninjas originally formed in the hills of Japan to escape brutal samurai law. They hid from the law studying ninjutsu to protect their friends and family from ruthless rulers.