The Gestapo investigated the July 20 plot thoroughly, so filmmakers had access to much documentation as they integrated the historical account with "Hollywood factors" in producing Valkyrie.[27] Peter Hoffmann, professor of history at McGill University and a leading authority on the German Resistance, was a consultant for the filmmakers. Hoffmann spoke of the film's accuracy, "[Valkyrie] gives a fundamentally accurate portrait of Stauffenberg and his co-conspirators. There are details which must be counted as liberties. But, fundamentally, the film is decent, respectful and represents the spirit of the conspiracy."[122] The Scotsman reported of the film's accuracy, "Valkyrie... sticks pretty closely to the story of the failed conspiracy to topple the Nazi regime... it implies that the plot came closer to success than it really did. But the basic facts are all present and correct."[123]
While von Stauffenberg listens to Richard Wagner's "Ride of the Valkyries" in the film, in reality the colonel hated Wagner. In addition, von Stauffenberg's elder brother Berthold was also omitted from the film.[124] Bryan Singer purposely left out some of von Stauffenberg's "macho" moments in writing the character, such as the colonel's refusal of morphine to avoid addiction. He explained the removals, "There were things I actually left out because I knew people would think we were making them up... imagine Tom Cruise saying 'No morphine!' People would think it's a contrivance."[125] In the film, von Haeften steps out in front of von Stauffenberg at the firing range, but when filmmakers attempted to reconstruct the scene based on eyewitness testimony and photographs, they discovered that the shots that killed von Haeften would also have killed von Stauffenberg, who was actually shot shortly after. Another alteration was to the portrayal of Carl Friedrich Goerdeler, played in the film by Kevin McNally. Goerdeler was written in the film to be antagonistic, dramatically representing the friction and conflict that existed within the conspiracy, though filmmakers considered him a "much more moral character" in reality.[13]
British novelist Justin Cartwright, who authored the book The Song Before It Is Sung about one of the plot's conspirators, wrote, "The film is true to most of the facts of the plot, but fails to convey any sense of the catastrophic moral and political vortex into which Germans were being drawn." Though not depicted in the film, von Stauffenberg was persuaded to become involved in the plot by his uncle, Nikolaus Graf von Üxküll-Gyllenband, who was disenchanted with the Nazis. The film also did not explore von Stauffenberg's philosophy and background, which Cartwright felt fit the German tradition of Dichter und Helden ("poets and heroes"). Cartwright described how von Stauffenberg was an appropriate leader for the plot: "He was the man who unmistakably wore the mantle of a near-mystic German past, a warrior Germany, a noble Germany, a poetic Germany, a Germany of myth and longing." The novelist felt that Cruise's portrayal was more akin to one as a "troublesome cop". Cartwright also noted that the film did not raise the question of what kind of Germany von Stauffenberg had in mind if the plot succeeded.[126]
