First film to ever get an X rating for violence in the US. American newspaper ads carried the quote "NOTICE: The MPAA has rated this film unsuitable for viewers under the age of 17 because of its extraordinary fight sequences."
Became public domain after copyright wasn't renewed.
The blind assassin wielding a cane sword is an homage to the Zatoichi blind swordsman films starring Shintarô Katsu.
Capcom's fighting-game franchise was named in honor after the US title of this film, having to drop the word "The" out of the title to differentiate the logo as "Street Fighter".
In the movie The Last Dragon (1985), Taimak's character Leroy Green would wear an espionage outfit that is the exact same black gi that Takuma Tsurugi/Terry Sugury dons.