According to "Film Review 1974-1975", this movie was "based on the famous Philby spy case (and was) a parallel to the famous Philby spy case."
The date in which the most sophisticated and deadly spy network in the world advised the President of the United States to step outside all legal channels to preserve the security of the country was October 15, 1972. The date in which they thought they may have made an incredible mistake was September 15, 1973.
The opening prologue states: "That which enables a wise ruler and a good general to strike, to conquer and to attain goals beyond the reach of ordinary mortals is "Prior Knowledge" SUN TSU (fifth century B.C.). Some versions of this movie feature the following title card addenda to this movie's prologue: "In the modern world, this 'prior knowledge' is synonymous with 'Secret Services'. Novelists call it...'Espionage'."
In this movie, Yul Brynner played Russian Colonel Alexei Vlassov. As such, Brynner played a character of his own nationality. Brynner's full birth name was Yuli Borisovich Bryner.
Sir Dirk Bogarde (Philip Boyle) worked for just five days on this movie.