The Battle of Chickamauga took place in the mountains of Tennessee in September of 1863. In a significant Union defeat, the Northern Army of the Cumberland, led by Major General Rosecrans, faced up against a combination of Southern troops commanded by Generals Bragg and Longstreet, with the Confederates outnumbering the Union soldiers by as much as twenty thousand soldiers. The battle was characterized by "chaotic confusion, bitter fighting, and terrible disaster", and although the North was soundly trounced, the Southern victory was not compete; "the left wing of the Army of the Cumberland had held firm under the command of General George Thomas", standing up against a force twice their number.
Although they had forced General Bragg to cease his offensive and allow them to return to Chattanooga after the battle, the left wing of the Army of the Cumberland faced starvation after the Battle of Chickamauga when snipers made it impossible for food or provisions to reach their camp. Reinforcements finally arrived in the form of detachments from the Armies of the Potomac and Tennessee, and General Ulysses S. Grant came down in person to direct the next strike against the Confederates. The Army of the Cumberland, feeling that they were looked down upon as "a third rate army" by the other two detachments, performed their assignment in the assault with uncommon zeal. They were instrumental in breaking down the center of the Confederate line and forcing the divided Southern troops to retreat, leaving Chattanooga in the hands of the Union Army (Chapter 11).