When Ben Affleck first arrived on the set, he told director Phil Alden Robinson, "Nice working with you again." Robinson said, "What do you mean 'again'?" Affleck explained that when Robinson was filming the scene in Boston's Fenway Park for Field of Dreams (1989), he and Matt Damon were amongst the thousands of extras.
Ciarán Hinds (President Nemerov), who did not previously speak a word of Russian, learned all of his large chunks of Russian dialogue in two weeks.
The spray can that John Clark (Liev Schreiber) uses to cut through the chain-link fence is supposed to be a real-life CIA chemical spray known as "Ice Piss". When asked if a real can of Ice Piss could be acquired for the scene, the technical advisor said "I don't want to go to prison!"
Director Phil Alden Robinson changed the villains from Islamic extremists (in the novel) to Neo-Nazis. This was done because, prior to the September 11, 2001 attacks, he did not believe Arab terrorists could plausibly accomplish all that was necessary for the plot to work on film. After 9/11, the production staff had to review how to present the movie to the public.
The title is paraphrased from a Sir Winston Churchill speech: "Why, you can take the most gallant sailor, the most intrepid airman, or the most audacious soldier, put them at a table together, what do you get? The sum of their fears."