Sergio Leone wanted Henry Fonda for the role of Col. Mortimer, but Fonda turned it down. Leone next approached Charles Bronson, who wasn't interested, and Lee Marvin, who refused it because he had just signed to make Cat Ballou (1965). It was then that Leone offered the role to Lee Van Cleef, who hadn't worked in films since How the West Was Won (1962), although he had worked fairly steadily in television. Van Cleef thought that Leone only wanted him for a few scenes, and was astounded when he discovered that he was actually to be the co-star.