While researching the novel in the early 1970s, author Frederick Forsyth pretended he was actually financing a coup d'etat in Equatorial Guinea. The pretense allowed Forsyth access to a number of underworld figures, including mercenaries and arms dealers. Forsyth has since commented that the arms dealers were the most frightening people he has ever met.
Tom Berenger has said in interviews that around half of his role was omitted from the final release print. When executive producer Norman Jewison asked him to go on a promotional trip to Japan, the angry actor vociferously refused. According to Berenger, Helen Shaver, who played his wife in the film, was totally eliminated from the release print.
The "XM-18" grenade launcher used in the movie is a real-life weapon. It is called the Manville Gun. It was named after its inventor, Charles Manville, who designed the gun in 1935 as a 12gauge multi-barrel shotgun (24 shot capacity). However, the XM-18 in DOW is based on an updated 1936 design as a 25mm grenade launcher with an 18 shot capacity (hence the "18" in XM-18). The movie version was still considerably more powerful than WWII era 25mm grenades were capable of. Unable to interest the military in his design, Manville's company stopped making the weapon. Ironically, in the early 1980's, the movie Dogs of War served to generate some interest from the military. Utilizing updated manufacturing processes and materials, the XM-18 type grenade launcher has actually seen some military service as a 25mm (18 shot) or 40mm (12 shot) grenade launcher. It is used by US Special Forces as well as some South American and African countries. With a range of between 150-350 meters, and with modern explosive technology, the 25mm grenade is fully capable of causing as much or more damage as was portrayed in the film. The 40mm grenade version uses the same projectile as is used in the Mk 19 grenade launcher which is widely used in the US Army. The current manufacturer is the Hawk Engineering Company who makes it under the designation MM-1.
Christopher Walken said he has been told by several people who saw this film, that the corruption Shannon encounters at the airport in the fictional African country he visits, is surprisingly realistic as they had similar things happen to them.