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. Many details of the actual escape attempt were changed for the film, including the roles of American personnel in both the planning and the escape. While the characters are fictitious, they are based on real men, in most cases being composites of several people. The screenwriters significantly increased the involvement of American POWs; a few American officers in the camp initially helped dig the tunnels and worked on the early plans. However, they were moved away seven months before the escape, which ended their involvement.[36][37] The real escape was by largely British and other Allied personnel, with the exception of American Johnnie Dodge, who was a British officer.[30] 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 who was the real-life "tunnel king", was engaged as a technical advisor for the film.[38]
Ramsey tells Von Luger that it is the sworn duty of every officer to attempt escape. In reality, there was no requirement in the King's Regulations, or in any form of international convention.[39]
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.[40]
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.[41]
The film omits any mention 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 and assistance of any kind to aid their escape.[39] The need for such accuracy produced much eyestrain, but unlike in the film, there were no cases of blindness. Some, such as Frank Knight, gave up forging because of the strain, but he certainly did not suffer the same ocular fate as the character of Colin Blythe in the film.[39] In fact, no one in the film says that Colin Blythe's blindness is the result of eyestrain. He identifies his problem as "progressive myopia", suggesting that he has not only heard of the condition but has also been diagnosed.
The film depicts the escape taking place in ideal weather conditions, whereas at the time much was done in freezing temperatures, and snow lay thick on the ground.[39] In reality 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).[42]
In the film, Hilts incapacitates a German soldier for his motorcycle, Ashley-Pitt kills Kuhn, a Gestapo officer, when he recognizes Bartlett waiting to pass through a Gestapo checkpoint at a railway station and Hendley knocks out a German guard at the airfield. Sedgwick witnesses the killing of German officers at a French Cafe by the French resistance. No German personnel were killed or injured by the real escapees.
Three truckloads of recaptured POWs drive in three directions. One truck contains 20 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 have the same manner; in reality, the POWs were shot individually or in pairs. The majority of the POWs were killed by pistol shots taken by Gestapo officers; however, at least ten of them were killed in a manner like that portrayed 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.[43][44][45][46][47][48][39] 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).[49]
In 2009, seven POWs returned to Stalag Luft III for the 65th anniversary of the escape[50] 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, who tries to scale the fence, and the actual 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.[30] British author Guy Walters notes that a pivotal scene in the film where MacDonald blunders by replying in English to a suspicious Gestapo officer saying, "Good luck", is now so strongly imprinted that historians have accepted it as a real event, and that it was Bushell's partner Bernard Scheidhauer who made the error. However, Walters points out that an historical account says that one of the two men said "yes" in English in response to a Kripo man's questions without any mention of "good luck" and notes that as 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, and says the "good luck" scene should be regarded as fiction.[39]
