For Whom the Bell Tolls was a romantic movie filmed on Earth in the year 1943. The movie featured Gary Cooper as Robert Jordan and Ingrid Bergman as María.
This film was found in the motion picture library aboard the Enterprise in 2151 and was the main feature around the time when the Enterprise visited Valakis. The movie brought tears to Commander Trip Tucker's eyes, though he denied the film as being the cause. (ENT: "Dear Doctor")
The name of this particular movie wasn't provided in the final draft script of "Dear Doctor", which was clearly written before
For Whom the Bell Tolls was selected.