Trapped in Chattanooga and nearly starved into surrender, Grant's army broke free and stormed two Confederate mountain fortresses in a campaign that opened the gateway to the Deep South.
After Chickamauga, Bragg's Confederate army besieged Rosecrans's Union forces in Chattanooga, cutting off their supply lines. Within weeks the Union army was on half rations and horses were dying of starvation — Chattanooga looked like it might become a catastrophic Union surrender.
Lincoln sent Grant to take command, and Grant's first act was to reopen a supply route. Within days of his arrival, Union forces seized a river crossing and opened the 'Cracker Line' — a supply corridor that ended the starvation and restored the army's fighting capacity in time for an offensive.
On November 24, Hooker's forces attacked Lookout Mountain in thick fog — a battle romanticized as the 'Battle Above the Clouds.' They swept Confederate defenders off the mountain, which had seemed impregnable, in a single day's fighting that electrified the Northern public.
The campaign's most extraordinary moment came on November 25 at Missionary Ridge. Grant ordered a limited advance to the base of the ridge. Instead, without orders, Union soldiers simply kept going — charging straight up the steep face of the mountain while their commanders watched in disbelief and horror.
The unauthorized uphill charge worked. Confederate defenders, unable to fire down the steep slope effectively, broke and fled as Union soldiers crested the ridge. Grant, furious at the breach of orders, demanded to know who had authorized the charge — but the stunning victory silenced any punishment.
The Chattanooga campaign's consequences were immense: Bragg's army was broken and retreated into Georgia, Tennessee was permanently secured for the Union, and the road south to Atlanta was open. It was Grant's last great Western campaign before Lincoln gave him command of all Union armies.