Lead actor Burt Lancaster re-financed the picture to the tune of around US $150,000 when the picture's budget fell short during principal photography.
Major Asa Barker (Burt Lancaster) limps throughout this movie because Lancaster was recovering from a real-life injury to his knee. It was actually the second movie where Lancaster's knee problems had an effect on a movie's characterization. On Il treno (1964), Lancaster took a day off during filming to play golf half way through the shoot. On the links he stepped in a hole and re-aggravated an old knee injury. In order to compensate for the injury, John Frankenheimer had Lancaster's character shot in the leg, thus enabling him to limp through the rest of the shooting.
The title comes from Simonides of Ceos' Epitaph, a quote by Herodotus, the Greek historian, about the famous Battle of Thermopylae in 480 B.C. Greece. 300 Spartan soldiers held a mountain pass against the entire Persian army; they all gave their lives, but the delay allowed Greece to prepare for their victory at Salamis. The epitaph of the Spartan soldiers reads "Stranger, go tell the Spartans that here we are buried, obedient to their orders."
The south Vietnamese general's building shown about halfway into the movie is actually Throop Hall, which was located on the campus of Caltech in Pasadena, California. Visible in the foreground is Millikan pond and the bridge that both still exist. Throop Hall was torn down in 1971, so this image must have been file footage that was spliced into the movie, since the movie is copyrighted 1977.
Daniel Ford wrote the movie's source novel based on his experiences covering Vietnam in 1964 for "The Nation", one of forty was correspondents. Ford was part of a Special Forces "A" Team. The assignment he followed was code-named "Operation Blaze".