Gian Maria Volontè and Tomas Milian frequently clashed on-set due to their political beliefs - Volontè was an outspoken communist, while Milian had left his home country (Cuba) as Fidel Castro came into power. To build on their onscreen chemistry, Sergio Sollima also intentionally provoked the two actors into engaging in boxing matches with each other.
Sergio Sollima was inspired to write and direct a film that dealt with the exchange of moral values between two characters based on his experiences in fighting with the anti-fascist resistance in World War II. He noted that during that time, he witnessed acts of courage committed by young children with minimal life experience, and acts of cowardice committed by once-brave men. Sollima later expressed that this film was a personal favorite of the films he made.
There was a cut version screened on BBC 2 and released on video and DVD at 95 minutes. The full version is available from Germany on Koch Media Blu-ray and DVD. There is an English dubbed soundtrack, in which the cut sequences are subtitled on the DVD, and have English dialogue on the Blu-ray version, although here the missing sequences have a faint hollow effect. The best version ever came from Fletcher Video in 1982. Uncut, wide-screen, and no dialogue defects. This must now be very rare.