This was originally announced in 1964 as a starring vehicle for Gregory Peck.
Despite the fact that it was a European co-production and the presence of Ennio Morricone, Anthony Quinn and Charles Branson,this was actually filmed entirely in Mexico.
Anthony Quinn was on Variety's list of Top Ten Overpriced Stars of 1968.
William Flaherty, who wrote the screenplay, was a Jesuit priest.
Takes place in 1700s Mexico then ruled by Spain