Unless you are talking about the Civil War era, you have to mean General Dean, who was captured in Korea in 1950. There is an interesting followup to that case.
After Dean was freed, it was learned that he had been given LSD, apparently as a "truth serum". While a few years later, any college student could have recounted the effects of "Lucy in the Sky with Diamonds", at that time the drug was little known. So the scientists at the Army's biological warfare center at Ft. Detrick, MD, were tasked with finding out what it would do and whether Dean could have revealed classified information under its influence.
And that led to a tragedy when one of the scientists, who had volunteered to be a "guinea pig", suffered serious brain damage and committed suicide, or was murdered by the evil CIA, depending on who is recounting the story.