According to the article "Hollywood Goes to War" by Colin Shindler in the film history tome "The Movie", "Warner Brothers, who had made the one explicitly anti-Nazi film of the [US] pre-war period (1939, "Confessions of a Nazi Spy") were unofficially told by the [US] government not to make any more such pictures. In April 1940 the news filtered back to Hollywood that several Polish exhibitors who had shown "Confessions of a Nazi Spy" had been hanged in the foyers of their own cinemas."
Some well-known actors (including Anna Sten and Marlene Dietrich) refused to be in the movie fearing reprisals against relatives living in Europe. Many who did appear changed their names for the same reason, accounting for large number of aka's in the cast list.
Warner Bros. increased security throughout the production and some actors slept on the Warners lot. Sabotage was suspected when a boom holding one of the cameras collapsed, narrowly missing director Anatole Litvak.
A libel suit for $75,000 was filed on Monday, July 3, 1939 in U.S. Federal Court against Warner Bros. by Katherine Moog, in which she claimed that the picture "Confessions of a Nazi Spy" and its advertisements defamed her character. Plaintiff alleged that Warners, without her consent, used her name to exploit the picture and connected her with the character "Erika Wolf," played by Lya Lys.
When this movie was made, America was not part of World War II. At this time a number of Hollywood studios were pro-American involvement in the war. This movie is one of a number of films made during the late 1930s and early 1940s that represented pro-American intervention in the war, including such films as A Yank in the R.A.F. (1941), Man Hunt (1941), Foreign Correspondent (1940), The Mortal Storm (1940), and Sergeant York (1941).
According to the book "The Films of World War II" by Joe Morella, Edward Z. Epstein and John Griggs, "While this Warner Bros. film was not as sensational as its advance publicity led audiences of the day to expect, it was, nevertheless, the first out-and-out anti-Nazi film from a major American studio . . . [it] made its point by sticking closely to the facts of a real-life spy trial which had involved high officials in the [German Third] Reich as well as their American operatives . . . This film was instrumental in bringing about the 'Hollywood war-mongering' charges. Actors and producers received murder threats. American-based German officials screamed 'conspiracy!' and the film was subsequently banned by countries who feared offending Germany. In the United States, however, it was a popular success, prompting other studios to hurry production of more anti-Hitler films."
The exchange of papers for the number of patients in the military hospital are arranged for Lexington and 93rd St. This is the location of the famous 92nd St. "Y", in this case the Young Mans Hebrew Association.
Four character names within the movie were slightly different than those names listed in the end credits: Paul Lukas, billed as Dr. Kassell, was actually Dr. Kassel within the movie. Similarly, Lya Lys was Erica Wolff (not Wolf), Hedwiga Reicher was Mrs. Kassel (not Kassell) and Sig Ruman was Krogmann (not Krogman).