After the fall of Vicksburg, the Union turned its attention to Chattanooga, the 'Gateway to the Deep South.' The city controlled key rail lines and the route into Georgia. Rosecrans maneuvered Bragg out of middle Tennessee without a major battle, then feinted north while swinging his army through mountain gaps to threaten Chattanooga from the south. Bragg abandoned the city and retreated into Georgia. But reinforcements were coming - Longstreet's corps from Virginia, additional troops from other theaters. By mid-September, Bragg had nearly 65,000 men and was ready to fight. Rosecrans, his army spread across miles of rough terrain, was vulnerable.

Fighting began on September 19 as both armies probed through thick woods that made coordination impossible. Divisions fought blind, stumbling into enemies in the underbrush. The day ended in bloody stalemate. On September 20, Bragg planned a general assault on the Union left, hoping to cut them off from Chattanooga. But miscommunication delayed the attack for hours. Then came the Union's fatal error. Rosecrans, receiving faulty intelligence that a gap existed in his line, ordered a division to move - creating the very gap he feared. At that moment, Longstreet's 11,000 veterans struck. They crashed through the opening, rolling up the Union right. Rosecrans himself was swept away in the rout, fleeing to Chattanooga convinced his army was destroyed.

The army wasn't destroyed because George Thomas refused to retreat. As the right collapsed, Thomas gathered survivors on Snodgrass Hill and Horseshoe Ridge. For the rest of the afternoon, his men repulsed Confederate attacks, buying time for the army to reach Chattanooga. Thomas organized the defense, inspired the men, and held until nightfall allowed withdrawal. His stand saved the Army of the Cumberland from annihilation. Rosecrans, whose previous campaigns had been models of operational skill, never recovered from the disaster his panic had caused. He was relieved within weeks. Thomas's reputation soared - 'Rock of Chickamauga' followed him for the rest of his life and beyond.

Chickamauga was a Confederate victory - the only major one in the Western Theater during 1863. But Bragg failed to pursue. Instead of destroying Rosecrans's army, he besieged it in Chattanooga, trusting that starvation would accomplish what battle hadn't. Grant arrived in late October with reinforcements and a plan. In November, Union forces stormed the Confederate positions on Missionary Ridge in an assault that wasn't even supposed to happen - soldiers charged without orders, carrying the seemingly impregnable heights. Bragg retreated into Georgia. Chattanooga was secure. The path into the Confederate heartland was open. Chickamauga had delayed the inevitable by two months.

Chickamauga and Chattanooga National Military Park was the first and largest Civil War battlefield preserved by the federal government, established in 1890. The Chickamauga Battlefield Visitor Center includes a museum with artifacts and Fuller Gun Collection. A seven-mile auto tour follows the battle's major phases, with monuments marking unit positions - over 1,400 monuments, markers, and tablets cover the battlefield. Key sites include the Brotherton Cabin (where Longstreet's assault broke through), Snodgrass Hill (Thomas's defense), and Wilder Tower (offering panoramic views). The battlefield is heavily wooded, giving visitors a sense of the visibility challenges both armies faced. The park is located in Fort Oglethorpe, Georgia, about 10 miles south of Chattanooga. Chattanooga Metropolitan Airport (CHA) is nearby; Atlanta's Hartsfield-Jackson (ATL) is 100 miles south.