The music in the film became the subject of a minor but telling episode in the Cold War. Alfred Newman, the illustrious head of the 20th Century-Fox music department, scored this picture. It's not readily known who decided to incorporate genuine Soviet music into the film, but Newman's score featured compositions by the USSR's finest: Dmitri Shostakovich, Sergei Prokofiev, Aram Khachaturyan and Dominik Miskovský. All four composers signed (or were ordered to sign) a letter of protest that claimed their music was appropriated via a "swindle" in order to accompany this "outrageous picture". No individuals were named, except "the agents of the American Twentieth Century-Fox Corporation". None of the composers would have had the opportunity to have seen the movie, thus it is to be assumed that they were put up to this protestation by the Stalin regime. Interestingly, the four "protesting" Soviet composers were at that same time under severe scrutiny themselves for composing music that was construed as subversive to the Soviet state, and for a time their heads were on the chopping block. So it's also to be assumed that the four filed this protest as a gesture of their loyalty to Joseph Stalin (or, more likely, to save themselves from being executed). In any case, these composers were often obliged to make statements that they personally had nothing to do with. Coincidentally, Hollywood at this same time was beginning to be scrutinized by the House Un-American Activities Committee for signs of subversion in the United States, resulting its own blacklist. See Slonimsky, Nicolas "Music Since 1900" 5th Ed. p.1066-7.
Said to be one of the first Cold War movies. The Iron Curtain (1948) was one of several anti-Communist films made in Hollywood in its early days. Some others were Schicksal in Wien (1949), The Red Menace (1949), I Married a Communist (1949) aka Ich heiratete einen Kommunisten (1949) and The Whip Hand (1951).
Soviet sympathizers attempted unsuccessfully to disrupt location shooting in Ottawa, where Fox captured exteriors during a cold Canadian winter.
In 1945, Igor Gouzenko, a decoder at the Russian Embassy in Ottawa, defected, handing over 109 pages of documents that revealed a network of Soviet spies out to steal information about the U.S.' development of the atomic bomb. The result was a series of highly publicized trials leading to ten convictions. Among those implicated were a Member of Parliament and one of the scientists working on the Manhattan Project. Historians have also linked the investigation following Gouzenko's defection to the Rosenbergs in the U.S. and the Cambridge Five in England. The incident is often credited as the official start of the Cold War because of its revelations that former World War II ally the Soviet Union was secretly spying on the U.S.
In the book "Gouzenko the Untold Story", written by John Sawatsky, page 104 describes how Igor Gouzenko insisted on, and then met Dana Andrews for several hours at a house party during filming in Ottawa. Gene Tierney was a no-show.