The building blown up in the opening sequence in the film was an old San Francisco Fire Department building that was scheduled for demolition. Sam Peckinpah filmed the implosion from the upper floor windows of the Hyatt Regency Hotel, which was directly across the street.
The graphic violence in the original cut of the film was cut by Sam Peckinpah so he could obtain a PG rating for the film, instead of an R.
In 1977, James Caan said he only did the film because his advisers told him to work with Sam Peckinpah, and he rated it a zero on a scale to ten.
The final sequence was filmed aboard a "Victory" cargo ship that served in World War II and the Vietnam War, and also on-board the Mothball Fleet in Suisun Bay.
In preparation for the film, Robert Duvall and James Caan took lessons in mastering their characters' skills with Duvall taking lessons in using a rifle with infrared scope, and Caan learning to disarm the film's villains with the use of a cane.