The eighteen-day siege of Knoxville from November 17 to December 4, 1863, stemmed from two interrelated causes. First, General Braxton Bragg, commander of the Army of Tennessee, desired to divert troops from the Federal army holding the city of Chattanooga. Second, Bragg wanted to rid himself of Lieutenant General James Longstreet. In September 1863 Longstreet's First Corps of the Army of Northern Virginia had been transferred to help repel the Federal thrust against Chattanooga and into north Georgia. Bragg's and Longstreet's combined forces badly defeated the Union Army of the Cumberland at Chickamauga and hemmed it inside the fortifications around Chattanooga. Shortly after this victory, Longstreet led an abortive cabal to remove the incompetent and unpopular Bragg from command, hoping to be named in Bragg's stead. When this revolt failed, Bragg detached Longstreet and his corps and ordered them to recapture Knoxville, which had fallen in early September to a Union force under the command of Major General Ambrose Burnside.
On November 5 Longstreet headed northward up the Tennessee Valley. He soon found himself in a footrace with Burnside, who had decided not to contest Longstreet's advance and quickly fell back from his forward position near Loudon. Longstreet failed in his attempt to get between the Federals and Knoxville as Union soldiers fought a rearguard action at Campbell's Station while Burnside withdrew into the fortifications surrounding the city.
Longstreet's troops sealed off all approaches to Knoxville, hoping to starve the garrison into submission. Longstreet and his chief engineer, Brigadier General Danville Leadbetter, determined that the old Confederate Fort Loudon (renamed Fort Sanders by the Federals in honor of Brigadier General William Sanders, who had been killed in a rearguard action near the city) offered the weakest link.
The November 29 attack led by Major General Lafayette McLaws failed utterly. Confederate soldiers lost the element of surprise after capturing the Federal picket line the night before by alerting the garrison when, in the predawn darkness, the advancing column became entangled in telegraph wire strung across the line of attack. The Confederates then discovered that the ditch they thought to be shallow was in actuality four to eight feet deep. The walls of the fort were slippery with ice from water poured upon them by the defenders; even worse, the necessary scaling ladders could not be found. Additionally, the attacking column converged to a narrow front that jammed the units together in the ditch, creating a slaughter pen. The Federals laid down a murderous artillery and musket fire and hurled axes, lighted shells, and billets of wood upon the crowded Southern infantry. The few Confederates who made it inside the fort were quickly killed or captured.
It was all over in about twenty minutes. The Confederates suffered 813 casualties, a quarter of whom were prisoners who had surrendered rather than run the gauntlet of fire back to their own lines. Federal losses totaled five dead and eight wounded. When Longstreet learned of Bragg's rout from Chattanooga and Sherman's approach from the south, he lifted the siege on December 4 and withdrew into winter quarters in upper East Tennessee.