The first of two British-financed westerns that Telly Savalas was involved with, the other being Pancho Villa (1972). He was also involved with the same production team's Horror Express (1972). Due to his expensive lifestyle and gambling habits, he was always happy to take on a role with a decent paycheck.
Michael Craig writes in his memoirs that his character scenes were shot a couple of months after the rest of the film was finished.
Al Lettieri was dubbed, and some of Robert Shaw's lines were dubbed.
During the shooting; Robert Shaw and Telly Savalas competed in arm wrestling and table tennis between the takes.