One of the main reasons for the movie being filmed in B&W was the Nazi flags. The French authorities refused to allow red and black Nazi flags to fly in Paris, even for a movie. They agreed only to have black and gray flags.
A French postman felt off his bicycle on the Champs Elysées, when he saw some extras dressed as German soldiers crossing the avenue during a lunch pause. He ran out screaming, "They're back! They're back!"
The first unit that reached Paris belonging to the 2nd Armored Divison of Gen. Henri Leclerc was formed by former Spanish republican soldiers. In the scene where the first halftracks enter Paris, you can see the names "Madrid" and "Teruel", two Spanish cities, written on their sides.
Some of the French actors, such as Charles Boyer, Leslie Caron and Jean-Pierre Cassel, dubbed their own dialogue into English. The American theatrical release of this film had all the French dialogue parts of the film dubbed into English language.
Every actor spoke their own language during filming, and thus the movie was originally intended as trilingual in French, German and English (with a bit of Swedish). However, no home video release has as of yet reproduced this, preferring instead to provide audio tracks fully dubbed into one language or another.
Several of the French civilian vehicles are shown with cylindrical tanks on their roofs. These contained compressed natural gas and are accurate. During WW2 over 60,000 French cars were converted to natural and wood gas fuel.
The meaning and relevance of the film's title "Is Paris Burning?" refers to the order given by Nazi high command to bomb and destroy the city of Paris when it appeared that Allied forces were poised to take it. During the film, as the resistance and Allied forces are taking back the city of Paris, on the phone can be heard a high-ranking Nazi (probably Adolf Hitler, played by Billy Frick) ask, "Is Paris burning?" Apparently, during August 1944 Hitler ordered the German Commander of Paris, Gen. Dietrich von Choltitz (played by Gert Fröbe), to destroy the city, and asked that question of von Choltitz when he received reports that Allied forces of his Chief of Staff of Operations, Gen. Alfred Jodl, and not to von Choltitz.
French actor Claude Rich actually plays two characters in this film. Rich plays the young Lt. Pierre de la Fouchardière and the mustached Gen. Henri Leclerc, de la Fouchardière's commander, but Rich is only credited for playing Leclerc. In real life, as a teenage boy during the Second World War, Rich was staring at some German soldiers in the street, and the real de la Fouchardière saved him from possible harm when he saw the boy in the street and got him to come into the building he was in and away from the Germans.
During this movie a Nazi propaganda film is shown, saying that Poland had attacked Germany and started the war. The truth is that the Germans staged a "Polish attack" by dressing Polish prisoners in military uniforms and filming the "invasion" as an excuse to invade Poland.
An article in the 7 November 1966 issue of 'Boxoffice' reported that four featurettes were made to promote the movie: "He Must Find There Nothing", in a 20-minute and a 10-minute version, a making of the production and how locations had to be modified to reflect the 1944 period; "Reality Must Not Be Left to Chance", 10-minute short behind the scenes; and a fourth featurette about composer Maurice Jarre.
This film's opening prologue states: "This is not the story of a beautiful city - not as we know it today - but as it was in its most perilous and also its most glorious hours. Paris in 1944, after four years of bitter occupation, was seething on the verge of revolt against the Nazi oppressors. With the allies almost at the doorstep, the French Resistance in the city, composed of many divergent groups, struggled bitterly among themselves to find the way to liberation. TIME WAS TERRIBLY SHORT . . . "
The video game Sakura Wars (1997) 3 has a subtitle "Pari wa Moeteiru ka" which is from the Japanese language meaning 'Is Paris Burning?' whilst a level in the video-game Commandos 2: Men of Courage (2001) is also entitled 'Is Paris Burning?'
After this movie was made and released, writer-lyricist Maurice Vidalin added lyrics to this films music score which had been composed by composer Maurice Jarre. This new music became a French patriotic anthem sung by Mireille Mathieu under the new title, "Paris en colère".
Before the shooting of the movie, General De Gaulle discussed at the Elysee palace with the director René Clément about the way he wished the film to be made. De Gaulle refused to be shown in the film and insisted that the French resistance was depicted as the true savior of Paris and not the American army.
Orson Welles, who had a small role in the movie, was arrogant with the director René Clément and refused to directly talk to him, although Welles spoke fluent French. He used Yves Boisset as a translator. According to Boisset, Welles was jealous that Clément was given a mammoth budget movie to direct.