In September 1863, troops under the command of Union General Ambrose Burnside marched through the Cumberland Gap, occupied Knoxville, and began constructing fortified earthworks there. In an effort to prevent Burnside from reinforcing the Union forces in Chattanooga, Confederate troops commanded by General James Longstreet began besieging Knoxville on November 17, 1863.
Longstreet believed that the best place to break through the Union lines was west of the city at Fort Sanders. The fort sat on a 70 ft. high hill, and its 15-foot-high earthen walls were surrounded by a ditch 12 ft. wide and 8 ft. deep. Longstreet gambled on a surprise assault of the fort. The attack began on the morning of November 29, but it was poorly planned and executed. Upon reaching the ditch surrounding the fort, Confederate troops did not have any ladders for scaling the walls and, massed in the ditch, they were subjected to ferocious fire from the Union troops manning the walls of the fort. Longstreet called off the attack after just 20 minutes, at the cost of 813 casualties to the Union Army's 13. After one of the most lopsided defeats of the Civil War, Longstreet withdrew from Knoxville on December 4.