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Working titles for the film were The Extra Edge and The Phoenix. According to a November 1955 Hollywood Reporter news item, Britain's Exclusive Films (an alternate corporate name used by Hammer in the early 1950s) intended to make both an English language and German-language adaptation of Lawrence Bachmann's novel, The Phoenix, with Bachmann scripting and co-producing. Only the English-language version was made, and Bachmann's contribution, if any, to the finished script has not been determined. The film was shot on location in Berlin.
A May 1958 New York Times article indicated that director Robert Aldrich received unprecendented assistance from East Berlin authorities and equipment from DEFA Studios in East Berlin. The East Berlin Government in the Soviet sector of the city controlled Berlin's railways and, at Aldrich's request, offered complete cooperation in allowing the filming of an early sequence in the story as the soldiers, returning from the POW camps, arrive in the Berlin train station. The Daily Variety review noted that the voice-over narration seemed to be an "afterthought" and indeed, a portion of it contradicts the film when the narrator mentions six months having passed since one character's death yet "Eric" soon after states that three months have passed.