Question: was the great escape based on a real story

Answer: Yes, The film is based on Paul Brickhill's 1950 book of the same name, a non-fiction first-hand account of the mass escape from Stalag Luft III in Sagan (now Żagań, Poland), in the province of Lower Silesia, Nazi Germany. A heavily fictionalised version of the escape is depicted in the film. The film was based on the real events but with numerous compromises for its commercial appeal, such as including Americans among the escapees (none of whom were actually American). The characters are based on real men, and in some cases are composites of several men. However, many details of the actual escape attempt were changed for the film, and the role of American personnel in both the planning and the escape was largely fabricated. The Great Escape was made by The Mirisch Company, released by United Artists, and produced and directed by John Sturges.