The reason the exteriors have so much fog and smoke was because the filmmakers were trying to hide the fact that the studio, Elios Studio near Rome, needed to be renovated.
John Steiner was afraid of horses, so Sergio Martino had him stand on wooden planks while shooting his close-ups so it looked as if he were riding a horse.
The lyrics to the theme song: "You're alone. A solitary man. And when the sun goes down, your memories back around with you and your heart is breaking down. This here was your father's land. Nothing bad, you can't pretend. You love justice and you love peace. When the time will come to kill, to destroy who loves to kill and your hand will stop the axe and your conscience will be satisfied. Yes. You're a good man, no one will put you down. Your feel is right, down worry man. Keep going, you know the way. That's the right way. Keep going. You're alone. A solitary man."
Mannaja (The Italian word for hatchet) is pronounced in Italian as "Mannaya".