They were Americans and they were prisoners. That's the starting point: 5,000 men captured by the British during the war of 1812 and confined in Dartmoor Prison, a bleak complex of stone buildings near Plymouth, England.
900 of the men were Black, and the white prisoners demanded segregation of the races, decades before Jim Crow laws made such divisions mandatory among free Americans.
The story is told in great detail by historian Nicholas Guyatt in his book The Hated Cage: An American Tragedy in Britain's Most Terrifying Prison.
The author pays a visit to lay out the facts of the remarkable story.