Michael Lonsdale was dubbed by Marc Smith. Lonsdale appeared in this spy movie, which was released just a few years after Lonsdale played the villain Drax in Moonraker - Operazione spazio (1979).
The East Berlin locations in this movie were filmed in the French locations of Lille in Nord, and Strasbourg in the Bas-Rhin.
For his character in this movie, Martin Sheen had to wear disguises. Sheen said that this was the first time he had worn disguises since "The Apple Man" during the late 1960s.
Director Jeannot Szwarc once said of this movie around the time it was first released: "I'd been looking for something like this, something like Il terzo uomo (1949). I'm a classicist, I guess. I always like to do classical genres of film. And there hasn't been a film for years like Il terzo uomo (1949) which, if anything, is the style of this one, with something of Z, l'orgia del potere (1969) in it, too."