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.
In Bill Sokal office it can be seen clearly painting portrait of US President John F. Kennedy. Bruce Greenwood who played as Bill Sokal, also played as US President John F. Kennedy in the movie Thirteen Days.
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.
At the beginning of the movie, some Colt M16 VNs can be seen handled by the platoon of soldiers, a few M60 machine guns, a Remington 870 Combat Shotgun, a couple of RPD Machine guns and some AK-47s in the hands of the Vietcong. Later on, the Marines arriving at the Embassy scene carried M16A2s, some carried Minimi M249 Machine Guns, and the Embassy Guards carried Mosberg Shotguns (unsure of the exact type), while the Yemenese carried AKs and SVD Dragunovs and various small arms.
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.