Burt Lancaster took a day off during shooting to play golf when the shooting was about half completed. 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 sequence in which Burt Lancaster evades an air attack on his locomotive by driving at full speed into a tunnel was based on an attack on the Great Western Railway during the war. A passenger train was pursued by a German fighter along the main line into Wales. Reaching speeds estimated at 90 mph (well above the wartime restrictions in place) the train successfully escaped into the tunnel under the River Severn in Gloucestershire and stopped beneath the river until the engineer judged that the danger had passed. The train was struck several times during the chase but there were no serious injuries.
In real life the museum's paintings were indeed loaded into a train for shipment to Germany, but fortunately, the elaborate deception seen in the movie was not really required. The train was merely routed onto a ring railway and circled around and around Paris until the Allies arrived.
The character of Mlle Villard is based on Rose Antonia Maria Valland - a French art historian, a member of the French Resistance, a captain in the French military, and one of the most decorated women in French history. As overseer of the Jeu de Paume Museum in Paris during the German occupation, Valland began secretly recording as much as possible about more than 20,000 pieces of art that had been brought to the Jeu de Paume. She understood German and for four years kept track of where and to whom in Germany the plundered artworks were shipped. She provided the information to the French Underground and about railroad shipments of art so that they would not mistakenly blow up the trains loaded with art treasures. A few weeks before the Liberation of Paris, on August 1, 1944, Valland learned that the Germans were planning to ship out five last boxcars full of art, including many of the modern paintings which they had hitherto neglected. She notified her contacts in the Resistance, who prevented the train from leaving Paris. The movie was inspired by her 1961 non-fiction book "Le front de l'art: défense des collections françaises, 1939-1945" (The Art Front: Defence of the French Collections, 1939-1945).
John Frankenheimer said of this film, "I wanted all the realism possible. There are no tricks in this film. When trains crash together, they are real trains. There is no substitute for that kind of reality."
The budget doubled under John Frankenheimer, due to an emphasis on action and the filming of train wrecks, eventually reaching $6.7 million. United Artists felt compelled to step in and assert its completion rights, demanding that principal photography be finished in seven weeks.
Director Arthur Penn oversaw the development of the film and directed the first day of shooting. The next day was a holiday. Burt Lancaster, dissatisfied with Penn's conception of the picture, had him fired and replaced by John Frankenheimer. Penn envisioned a more intimate film that would muse on the role art played in the French character, and why they would risk their lives to save the country's great art from the Nazis. He did not intend to give much focus to the mechanics of the train operation itself. Frankenheimer said that in the original script Penn wanted to shoot, the train did not leave the station until page 90. The production was shut down briefly while the script was rewritten. Lancaster told screenwriter Walter Bernstein the day Penn was fired, "Frankenheimer is a bit of a whore, but he'll do what I want." What Lancaster wanted was more emphasis on action in order to ensure that the film was a hit--after the failure of his film The Leopard (1963)--by appealing to a broader audience.
The engine that crashes into a derailed engine was moving at nearly 60 mph. The crash was staged in the town of Acquigny, with extensive safety precautions and special insurance. Only one take was possible, and seven cameras were used.
Burt Lancaster only speaks twice throughout the last 33 minutes of the film. His final line, "Didont, get down! Run!" is said a little more than 27 minutes before the final scene of the movie fades out.
The air raid on the yards was filmed at Gargenville yard, outside Paris. More than 50 people under Lee Zavitz needed six weeks to plant and wire all the charges, which were blown up in less than a minute. This was done by a special arrangement with the French National Railway, which had been seeking to modernize the yard but lacked the funds to do so.
In the final confrontation between Burt Lancaster's Labiche character and the Nazi colonel played by Paul Scofield, the shooting conditions were so cold that Scofield reportedly had to talk while inhaling so clouds of warm breath wouldn't appear on film. His voice was looped in later.
According to the book the 'Variety Movie Guide', this movie was "Made in French and English in France, it was entirely lensed in real exteriors with unlimited access to old French rolling stock of the last war."
During the early parts of the movie, and the air raid scene, an armored locomotive can be seen. This locomotive was a French engine which was "mocked up" with plywood to resemble a German BP44 series armored locomotive. In some shots of it, if the viewer looks closely, they can see the plywood actually moving from vibrations of the locomotive.
The primary steam locomotives in the film are Class 230Bs, #739 (leads the military train Paris to Vaires), 517 (art train until Rive-Reine crash), 855 (rear engine in Rive-Reine crash), and 711 (art train post-crash). These engines were built from 1901 to 1912, and were nearing the end of their long service life in 1964.
In the opening sequence, the parade of major artists' names stenciled on packing crates - GAUGUIN, RENOIR, VAN GOGH, MANET, PICASSO, DEGAS, MIRO, CEZANNE, MATISSE, BRAQUE, SEURAT, UTRILLO - is immediately followed by the director's credit for John Frankenheimer.
As the art train is coming to its final stop where von Waldheim will be killed, we see a closeup of his face. Prominently placed in the background is a sign on the train, never shown earlier in the movie, that warns of "danger de mort": lethal danger. (It actually refers to the live wires that run above some tracks.)