The newspaper that Ashley-Pitt ('David McCallum') reads on the train is the 'Völkischer Beobachter', a real newspaper produced for 25 years by the National Socialist German Workers Party. It served as a propaganda sheet for the Nazis and helped bring Hitler to power. At its height, it had a circulation of approximately 1.4 million. The headline for the issue seen in the film translates roughly to "Day after day, the Soviets have high, bloody losses." Given that the escape in the film occurs in the summer of 1944, this too can be viewed as propaganda. The Nazis had transferred hundreds of thousands of troops to Normandy to stop the Allied advances after D-Day, allowing for the Soviet's to launch Operation Bagration on 22 June, which pushed the Nazis back into Poland by the beginning of 13 July and sparked the Warsaw uprising. In all, the Soviet advance caused German losses of approximately 670,000 dead, missing, wounded and sick, including 160,000 captured. Although the date of the escape is unclear, given the green pastures around the Alps that the escapees encounter, one can easily surmise that the newspaper was putting a positive spin on the battles in the east.
The real-life escape preparations involved 600 men working for well over a year. The escape did have the desired effect of diverting German resources, including a doubling of the number of guards after the Gestapo took over the camp from the Luftwaffe.
The real-life escape was on the night of 24 March 1944, and the ground was snow-covered. The German town near the prison camp, called Neustadt in the film, was really Sagan (now Zagan, Poland). Steve McQueen was born on March 24th.
The shooting of the recaptured escapees was one of the charges at the Nuremberg War Crimes Trial of Hermann Göring and other Nazi leaders.
There are seven different languages spoken or sung in the movie: English, German, French, Russian and one word in Spanish as well as two words of Latin "Lanius Nubicus" when Flight Lieutenant Blythe is describing the masked shrike or butcher bird in the forgery scene. There is also a song in Scottish Gaelic where Ives and MacDonald are singing in the 4th of July scene just before "Tom" is discovered.
Though seemingly hauled away for allowing the escape to take place, the Commandant was actually arrested for being involved in a brisk black-market operation, a fact unearthed during the Gestapo investigation of the escape.
When celebrating the Fourth of July and pouring alcohol, Hilts (Steve McQueen) is thrown off by an ad-lib by Goff (Jud Taylor). While Hilts is drinking, Goff says, "No taxation without representation." McQueen jumps out of character and gives him a look (and mouths, "What?") The director must have signaled to "just go with it" and the scene continues. But it is an obvious ad-lib.
When the Bavaria Studio's backlot proved to be too small, the production team obtained permission from the German government to shoot in a national forest adjoining the studio. After the end of principal photography, the company restored (by reseeding) some 2,000 small pine trees that had been damaged in the course of shooting.
Whenever a prisoner attempting escape is told "good luck" by a fellow prisoner, the escape fails. Ironically, these are the same words that the German officer uses to capture Bartlett and MacDonald near the end of the film.