Originally, Colonel Winter was supposed to smoke cigars. James Gandolfini pleaded with director Rod Lurie to drop the idea because he felt smoking cigars would remind audiences too much of Tony Soprano, his star-making role in The Sopranos (1999).
James Gandolfini reportedly was reluctant to accept the role of Col. Winter because he didn't understand the story and had never served in the military himself. He committed largely on the strength of a lengthy speech Winter delivered in the original script; ironically, that entire scene was cut from the final film.
The main score of the movie, composed by Jerry Goldsmith, was named "September 11th 2001", because it was recorded on that day. Also, the movie's posters were changed after 9/11 because they showed an American flag flying upside-down; a new poster was put up featuring faces of the cast.
The finished film's storyline for Gen. Irwin and Col. Winter diverted sharply from David Scarpa's original screenplay. While both the script and the film begin by presenting Irwin as the sympathetic lead character and Winter as the bullying antagonist, Scarpa wrote the film's 2nd and 3rd acts to show that Winter was a good man and Irwin was a violent taskmaster who brutalized the other inmates into joining his crusade to get rid of the Colonel. The script was re-written when Robert Redford signed up to the film, with Irwin remaining the generally noble campaigner against Winter's reign of cruelty.
One of the medal ribbons on General Irwin's uniform (which he wears when he first arrives at the prison) is the Medal of Honor, the U.S. Military's highest decoration, awarded for acts of extreme bravery in combat. It's the blue one at the top of his rows of ribbons.
In the opening minutes of the movie, Colonel Winters remarks "My God, they should be naming a base after him!", referring to the arriving prisoner General Eugene Irwin. Actually, the US Army already has a Fort Irwin, located in the Mojave Desert in California, although it is named for Major General George LeRoy Irwin.