Director Istvan Szabo has stated that in preparing for this film, he took as much inspiration from Joseph Roth's THE RADETZKY MARCH (a novel about one family's tradition of service to the Emperor) as he did from the facts of the Alfred Redl case. In COLONEL REDL, the Archduke says he needs a scapegoat - specifically, someone who is Redl's "double" - and when Redl can't provide one, he makes himself available. That's what the loyal Austro-Hungarian subject did; he served the Empire, even if it meant putting himself in jeopardy.
In reality, Russian agents had uncovered Redl's homosexuality in the early 1900s & had been blackmailing him for close to a decade, learning Austria's plans for general mobilization and various military operations. It has been speculated that tens of thousands of Redl's compatriots died because of his treasonous acts.
I was not aware of the Roth connection, though it makes sense. The credits claim Colonel Redl's based on John Osborne's play A Patriot for Me, but the two works have almost nothing in common.
Although I enjoy Colonel Redl I always wondered about its characterization of Redl. From reading biographies of the man he's hardly the principled fellow shown in the movie. Probably more victim than villain but still not far from a hero.
"The melancholy truth was that his glorious golden head had nothing in it."