The film was largely fictional, with changes made to increase its drama and appeal to an American audience and to serve as vehicle for its box-office stars. While the characters are fictitious, they are in most cases composites of several real men. The screenwriters significantly increased the involvement of American POWs. While a few American officers in the camp initially helped dig the tunnels and worked on the early plans, they were moved away seven months before the escape, which ended their involvement.[35][36] The real escape was mostly by British and other Allied personnel, with the exception of American Johnnie Dodge, who was a British officer.[29] The film omits the crucial role that Canadians played in building the tunnels and in the escape itself. Of the 1,800 or so POWs, 600 were involved in preparations: 150 of those were Canadian. Wally Floody, an RCAF pilot and former miner, the real-life "tunnel king", was engaged as a technical advisor for the film.[37] In the film, Ramsey states that it is the sworn duty of every officer to attempt escape. In reality, there was no such requirement either in the King's Regulations or in any form of international convention.[38]
The film shows the tunnel codenamed Tom with its entrance under a stove and Harry's in a drain sump in a washroom. In reality, Dick's entrance was the drain sump, Harry's was under the stove, and Tom's was in a darkened corner next to a stove chimney.[39] Former POWs asked the filmmakers to exclude details about the help they received from their home countries, such as maps, papers, and tools hidden in gift packages, lest it jeopardise future POW escapes. The filmmakers complied.[40]
The film omits that many Germans willingly helped in the escape itself. The film suggests that the forgers were able to make near-exact replicas of just about any pass that was used in Nazi Germany. In reality, the forgers received a great deal of assistance from Germans who lived many hundreds of miles away on the other side of the country. Several German guards who were openly anti-Nazi also willingly gave the prisoners items that would aid their escape.[38] The need for accuracy in the forgeries produced much eyestrain, but unlike in the film, there were no cases of blindness. While some men, including Frank Knight, gave up forging because of the strain, no one suffered the same ocular fate as the character of Colin Blythe in the film.[38]
The film depicts the escape taking place in ideal weather conditions, whereas at the time much was done in freezing temperatures with snow lying thick on the ground.[38] There were no escapes by aircraft or motorcycle: McQueen requested the motorcycle sequence, which shows off his skills as a keen motorcyclist. He did the stunt riding himself (except for the final jump, done by Bud Ekins).[41]
In the film, Hilts knocks out a German soldier for his motorcycle, Ashley-Pitt kills a Gestapo officer, and Hendley attacks a German guard. In actuality, no enemy combatants were killed or injured by the real escapees. The movie depicts three truckloads of recaptured POWs ostensibly being driven back to the prison camp; one truck contains twenty prisoners who are invited to stretch their legs in a field, whereupon they are all machine gunned in a single massacre, with the implication that the other two truckloads meet the same fate. In reality, the majority of the escapees who died were shot individually or in pairs by Gestapo officers. However, at least ten were killed in a manner like that depicted in the film: Dutchy Swain, Chaz Hall, Brian Evans, Wally Valenta, George McGill, Pat Langford, Edgar Humphreys, Adam Kolanowski, Bob Stewart and Henry "Hank" Birkland.[42][43][44][45][46][47][38] The film depicts the three prisoners who escape to freedom as British, Polish, and Australian; in reality, they were Norwegian (Jens Müller and Per Bergsland) and Dutch (Bram van der Stok).[48]
Historian Guy Walters notes that a scene where MacDonald blunders by replying in English to a suspicious Gestapo officer who says "good luck" has become so strongly imprinted in the public consciousness that many historians have accepted it as a real event, ascribing the error to Bushell's partner Bernard Scheidhauer. However, Walters points out that an historical account states that one of the two men said "yes" in English in response to a Kripo officer's questions without any mention of "good luck". Walters also observes that since Scheidhauser was French and Bushell's first language was English, it seems likely that if a slip did take place, it was made by Bushell himself; therefore, he states, the "good luck" scene should be regarded as fiction.[38]
In 2009, seven POWs returned to Stalag Luft III for the 65th anniversary of the escape[49] and watched the film. According to the veterans, many details of the first half depicting life in the camp were authentic, e.g. the death of Ives while trying to scale the fence and the digging of the tunnels. The film has kept the memory of the 50 executed airmen alive for decades and has made their story known worldwide, if in a distorted form.[29]
