The film was made in occupied Germany. All scenes were photographed in the real locations associated with the story, including episodes in the American, French, British and Russian sectors of Berlin.
With the exception of Montgomery Clift and Paul Douglas, all military personnel in the film were actual members of the US military on duty in Germany at the time.
When shooting at the Brandenburg Gate, which was inside the Russian zone of occupation, authorities there erected a large loudspeaker that blared communist propaganda. The scenes were shot without sound and voices were dubbed in later.
Even though this was only his fourth film, Montgomery Clift already had a reputation for being difficult on set. Paul Douglas arrived in Berlin having been told by John Wayne (who had worked with Clift on "Red River" (1948) that "this kid is a little shit." During the filming of their first scenes together, Douglas realized that Clift was deliberately leaning into the scene, hogging his space. He stamped on the younger actor's foot and said, "Do that again and I'll break your fucking foot." Douglas and Clift didn't speak to each other for the rest of the shoot.
During the filming, the production got waivers signed by those who were in a shot and thought would be in the finished film, and paid them $500. Some men appeared but were never paid, and some who were paid had their appearances end up on the cutting-room floor.