In addition to writing the screenplay, Dario Argento directed some of the scenes uncredited. This was before his official directorial debut the following year with "The Bird With the Crystal Plummage" (1970).
Don Taylor did not complete " Five Man Army ". It was probably finished by either Dario Argento or Giulio Questi.
The film's English dub is the first, and one of a select few, in which Bud Spencer provides his own voice.
Partially shot on Once Upon a Time in the West (1968) location (the railroad and the farmhouse).