Braxton Bragg retreated from Tullahoma, Tennessee to Chattanooga, Tennessee while William S. Rosecrans advanced from Hoover Gap to Stevenson, Alabama. After a 6-week rest, Rosecrans Army of the Cumberland moved through the gaps in Lookout Mountain and Bragg withdrew from Chattanooga. As the Army of the Cumberland came out of the gaps in Georgia they did not know Ntsgg's Army of Tennessee was located betweensed a problem and began to move towards Chattanooga when Bragg, reinforced bn them and their objective, the Western and Atlantic Railroad. Rosecrans sey Longstreet's Corps from the Army of Northern Virginia hit Rosecrans' line with everything Bragg could muster. The 2-day battle of Chickamauga was the largest Confederate victory of the war.
After wintering in Ringgold for 3 months, Grant went to Washington to accept a promotion to General-in-Chief of the United States forces. Sherman was left to plan and execute the Atlanta Campaign on his own. Heading south along the Western and Atlantic Railroad Sherman engaged the Confederates, now under his old friend Joseph E. Johnston at Tunnel Hill, Dalton, and Resaca before heading into dense forest south of Kingston. As Hooker came out at New Hope Church he ran into John Bell Hood's Corps. Sherman wanted Thomas and O. O. Howard to turn the Rebel right flank, but they ran into the Union Army's nemesis Patrick Cleburne at Pickett's Mill. As the Union Army moved east north of the Confederate line, William Hardee struck them at Dallas.
Fighting along Johnston's line at Lost Mountain and Pine Mountain did little, but when Dan Butterfield struck Pat Cleburne at Gilgal Church, he became the first Union General to repulse the crafty Confederate. As Cleburne retreated, Johnston shifted his line from east-to-west to north-to-south and got ready for Sherman to strike near Kennesaw Mountain
Sherman, never one for a frontal assault tried to go around but Joe Hooker and John Schofield ran into John Bell Hood at Kolbs Farm. When that failed Sherman struck Johnson with 8,000 men along a 5-mile front, centered on Cheatham Hill. While the Confederate line did not break, in less than a week Johnston withdrew, first to the Smyrna Line and then to the Chattahoochee River Line.