Chuck Norris' opponent in the finale fight was 'Bill "Superfoot' Wallace' who was also John Belushi's bodyguard. In real life, Wallace was the one who discovered Belushi's body after his drug overdose.
The climactic night fight scene was shot in California in January and was prohibitively cold. Especially for Chuck Norris and Bill Wallace who were both barefoot and bare-chested throughout. The cameras would roll for a couple of minutes and then both actors would cover up and stand by a fire to warm up.
Director Paul Aaron was approached by American Cinema when the first director of the film, Ted Post, dropped out. Aaron had previously worked with the company on their (and his) first film A Different Story (1978). Although Chuck Norris was not a movie star at the time, Aaron was familiar with him as he had taken his kung fu obsessed stepson to see Enter the Dragon (1973). His stepson is Keanu Reeves.
Despite working with a screenplay by Oscar-winning writer Ernest Tidyman, director Paul Aaron did an uncredited rewrite on the script to "fit Chuck more". Tidyman was actually very ill during the making of the film and died shortly after it was completed.