James Webb provided the story for the film, based partly on his own military experience in Vietnam and his tenure as the Secretary of the Navy under President Ronald Reagan; in 2006, Webb was elected as Virginia's newest U.S. Senator.
A replica of the Marine Corps base at Camp Lejeune, North Carolina, was built at the Vint Hill Farm Station, South Manassas, Virginia. Approximately 800 Marines were hired for the combat, and other action scenes.
In Bill Sokal's office, a painting portrait of U.S. President John F. Kennedy can be seen. Bruce Greenwood who plays Bill Sokal, also played U.S. President John F. Kennedy in the movie Thirteen Days (2000).
When released in Spain, the movie title was literally translated resulting in "Reglas de compromiso". Engagement in English can be translated like in the original title as the behavior when two opposing forces come into contact or as near future wedding. Spanish language however uses different words for these two concepts, and the one referring to "wedding" was mistakenly used is the Spanish title creating a misleading title with no relation to the actual movie plot.
The trivia item below may give away important plot points.
The scene of Sokal viewing and destroying the tape after he sees it proves gunfire was coming from the crowd, was imposed by test audiences, according to William Friedkin. The film was supposed to leave ambiguous whether or not Childers did the right thing, depicting what happened through subjective viewpoints, and never revealing the objective truth of what occurred.