This film was denounced by former President (and Supreme Allied Commander in Europe during WW2) Dwight D. Eisenhower soon after its release in a press conference due to its glaring historical inaccuracies.

Robert Shaw earned $350,000 for his role as the German Panzer commander, more than he had earned in his entire career up to that point. That amount, after adjusting for inflation, would be equivalent to $3 million in 2022.

The film's senior military advisor, Brig. Gen. Meinrad von Lauchert, was the commander of the German 2nd Panzer Division during the real Battle of the Bulge. He then had the rank of Oberst (Colonel). Near the end an officer states that a German unit was within five miles of the Meuse River. Coincidental or not, that unit was commanded by von Lauchert.

The film makes it seem like the battle only lasted for a few days. In reality, it lasted just over a month.

Entirely shot in Spain ,which doesn't share much in the way of physical similarities with the snowy forests of the Ardennes in Belgium.

An article dated 12/2/65 and circulated by "The Washington Post" said that Dwight D. Eisenhower was "outraged" by this Warner Brothers movie. It said that Columbia Pictures had long had an epic movie in the works about the battle that had the cooperation of the Defense Department, as well as many of the generals who had been involved, including Eisenhower and Bernard L. Montgomery. The working title of Columbia's movie was "16th of December:The Battle of the Bulge." Michael Anderson was slated to direct from a screenplay by Byron Morgan and Tony Lazzarino, and the project was to be co-produced by Lazzorino and Kenneth T. Hoeck. The former president's son John S.D. Eisenhower was writing a companion history of the battle and serving as technical advisor. Anderson was quoted as hoping to have Van Heflin as Eisenhower, David Niven as Montgomery, John Wayne as Gen. George S. Patton and Laurence Olivier as Adolf Hitler. Shortly after Columbia announced that filming would begin during the winter of 1964, Warner Brothers registered the title "The Battle of the Bulge" and announced that it was going to make its own fictional movie, upsetting the plans for Columbia's epic. Columbia obtained an injunction against Warners, dropping it after Warners agreed that its picture would not use the names of any of the real-life figures that had contributed to Columbia's project, such as Eisenhower, Montgomery, Omar Bradley, Anthony McAuliffe, Patton and 10 other figures. The Defense Department had also urged a Federal Trade Commission action against the movie on the grounds that its title was misleading the public. When the article appeared it stated that Columbia's project would go forward, with filming to begin at Camp Drum near Watertown, NY, in the fall of 1966, but the project fell through and the film was never made.

The character of the German colonel was first intended to be real-life Panzer officer Joachim Peiper, the youngest man in the German army to make the rank of full colonel (SS-Standartenführer, the direct SS equivalent to an oberst or full colonel in the German army). A protégé of Reichsführer-SS Heinrich Himmler, the head of the Schutzstaffel (SS) and the third most powerful man in Germany after Adolf Hitler. Peiper was promoted to the rank at the age of 29. However, as he was still living at the time the film was produced and was still a committed Nazi, his character was quickly changed to a fictitious officer in the regular German army, so as not to give him any connection to the film or risk a libel suit. It was Peiper's unit (Kampfgruppe Peiper) of the 1st SS Division, Leibstandarte SS Adolf Hitler that was responsible for the massacre of American POWs in Malmedy, Belgium, depicted--although inaccurately--in the film. After the war he was convicted of war crimes and sentenced to death, but the sentence was commuted by the American Occupation Force because the trial had been fraught with illegalities, and Peiper wound up serving only 11 years in prison, despite having perpetrated war crimes on both the Eastern and Western fronts. He was assassinated at his home in France, likely by French communists, in 1976.

The small plane Col. Kiley (Henry Fonda) used for his reconnaissance missions is a Cessna L-19A/O-1 known in the military simply as the Bird Dog. This plane was used after WWII and is distinguished from the Piper L-4 Grasshopper by its raised cockpit, angled side windows and rounded rear window. These were not initially purpose-built military planes. The Cessna 305A was the military version of the 170, a small civil aviation plane popular with private pilots. Its ability to take off and land in relatively short distances on dirt fields made it very useful to troops operating in remote or forward areas. Though completely unarmed, they carried out a number of vital missions including reconnaissance, artillery spotting, supply drop and even air ambulance.

The climactic scene has Americans using burning fuel as a roadblock against approaching German panzers. A similar incident happened during the Battle of the Bulge. The 5th Belgian Fusilier Battalion guarded a fuel depot near Stavelot, Belgium, that stretched for a quarter-mile. When a German column approached the depot, the Belgians set fire to it by poking holes in the barrels with bayonets and rolling them onto the road before setting it on fire with tracers and matches. The Germans couldn't advance through the flames and couldn't go around because of the steep grades on the sides of the road and were forced to retreat.

German King Tiger tanks in this movie are actually American M47 Patton tanks, and the M4 Sherman tanks are actually M24 Chaffee tanks.

Part of this movie's music score utilized the World War II "Panzer Song" march.

The entire film was shot, edited, scored and prepared for release in an unprecedented eight months.

All the Germans are played by real Germans with the exceptions of Robert Shaw, Ty Hardin, and Barbara Werle.

Edward Dmytryk was the next in line to direct after Richard Fleischer turned it down but Jack L. Warner refused to work with him for being one of the Hollywood Ten during the McCarthy witch hunts of the 1950s.

Sergio Leone had wanted Charles Bronson for the Lee Van Cleef role in For a Few Dollars More (1965) but Bronson could not work around his commitment to this movie.

Producer Milton Sperling had first-hand experience of the type of wartime combat shown in the film---he had served with a documentary film unit in such WW2 battles as Iwo Jima.

The Spanish army supplied over 500 soldiers and 75 tanks for the production.

When Col. Hessler and Conrad share a glass of wine prior to meeting the tank commanders, there is a drawing of a Hetzer assault gun on the wall behind Conrad. It might well be the only depiction in this movie of an actual German armored vehicle.

The sequence of the train transporting the big guns was expanded with additional footage shot after principal photography. The extra footage consisted of POV shots from the front of the train and shot at a lower frame rate to make the train appear to be traveling very fast around the curves in the track. This was done to show off the Cinerama process in much the same way as the famous rollercoaster sequence in This Is Cinerama (1952). Much of this footage was removed from the general release version.

The name of the song that the Germans sing is "Panzerlied". However, only the first four lines of the song are actually sung.

Although it is claimed by knowledgeable film people that so-called Super-Cinerama was already in use as early as 1962, this was the first film that was actually advertised in the trailers as being shown in that format. The resulting image did not turn out to be larger than ordinary Cinerama, since the film was actually shot in Ultra Panavision, shown with one projector instead of three electronically synchronized ones, and merely blown up in size to fit the giant curved screen.

Some scenes were filmed on the crumbling sets of Samuel Bronston's The Fall of the Roman Empire (1964).

The red banner in Col. Hessler's quarters reads "Feind hort mit!" A rough translation is "The Enemy is listening!"

When the movie was released to video, some versions bizarrely included the original mid point cinema interval break lasting some five to ten minutes. This was even mentioned on the video casing cover as a bonus.

A documentary that outlines a more factual and non-fictionalized account of the Battle of the Bulge entitled The Battle of the Bulge... The Brave Rifles (1965) was made and released a year after this film.

Robert Shaw (an Englishman), Ty Hardin (an American) and Barbara Werle (an American) were the only native English-speaking actors who played Germans in the movie.

Stanley Baker was offered the Robert Shaw part, but was committed to Sands of the Kalahari (1965).

The small tank models on the German HQ's map board are HO-scale (1/87) Roco Minitanks, made in Austria. The German Bundeswehr actually used these little models in maneuver war games, but the firm was only founded in 1960 and they were therefore obviously not used in WW2. The small German tank models are real King Tigers, not the US M47 used in the battle scenes or depicted by the large model in the HQ.

Dino De Laurentiis apparently helped produce, but is uncredited.

Premiered at the Pacific Cinerama Dome Theatre in Hollywood on 12/16/65, the 21st anniversary of the battle.

Pier Angeli - who, only five years earlier, had been considered a big star - is billed sixth in the film, does not appear until the film is half-over, and then has only one scene.

This film was shot in Ultra Panavision for showing in Cinerama venues.

In early 1964, before the colossal flop of The Fall of the Roman Empire (1964), this film was announced as a Samuel Bronston production.

Richard Fleischer was originally announced as director.

The version of the film released on DVD contains approximately 1196 shots in 9397 seconds of action. This equates to an average shot length of about 7.9 seconds.

At the end of the movie when Lieutenant Weaver orders his men to start dumping fuel from various sources at the fuel dump down the hill towards the approaching German tanks, one of them turns on the tap in the rear of a fuel tanker truck. This truck, which was also closely surrounded on all three sides by stacks of barrels full of fuel, would have all been blown to pieces and resulting in a chain reaction which would have resulted in blowing up the entire fuel depot and everybody in it once the gasoline was set on fire as the flames would have backtracked all the way back up the hill to the source of the gasoline.

Towards the end of the movie when Lieutenant Weaver and his men are at the fuel dump, and after they killed the Germans that were posing as American military police, you see Lieutenant Weaver carrying a German MP 40 machine gun. The inference was that he got that weapon from one of the dead German imposters, but this would not have been possible since the Germans posing as American military police were all carrying American weapons

Epilogue: "This picture is dedicated to the one million men who fought in this great battle of World War II. To encompass the whole of the heroic contributions of all the participants, places, names and characters, have been generalized and action has been synthesized in order to convey the spirit and the essence of the battle."

Three years later, Charles Bronson and Henry Fonda would co-star memorably as adversaries in the iconic western Once Upon a Time in the West (1968), known in the US as "Once Upon a Time in the West."