The Thirteenth Tennessee Cavalry (U.S.), also known as the Fourteenth Tennessee Cavalry (U.S.) and Bradford's Battalion, was a regiment of the United States Army during the American Civil War. The Thirteenth was composed primarily of white, pro-Union soldiers from western Tennessee. Many had even fought for the Confederacy earlier in the war. The Thirteenth was assigned to Fort Pillow in 1864. They were under the command of Major Bill Bradford, and played a role in the Battle of Fort Pillow.
The Thirteenth Tennessee was actually one of two units by that name operating in Tennessee during the American Civil War. Harry Turtledove opted to use that name in the novel Fort Pillow, as most primary sources on the event use that name for convenience.