After the Tullahoma Campaign, Rosecrans renewed
his offensive, aiming to force the Confederates out of Chattanooga. The
three army corps comprising Rosecrans' s army split and set out for
Chattanooga by separate routes. In early September, Rosecrans
consolidated his forces scattered in Tennessee and Georgia and forced
Bragg's army out of Chattanooga, heading south. The Union troops
followed it and brushed with it at Davis' Cross Roads. Bragg was
determined to reoccupy Chattanooga and decided to meet a part of
Rosecrans's army, defeat them, and then move back into the city. On the
17th he headed north, intending to meet and beat the XXI Army Corps. As
Bragg marched north on the 18th, his cavalry and infantry fought with
Union cavalry and mounted infantry which were armed with Spencer
repeating rifles. Fighting began in earnest on the morning of the 19th,
and Bragg's men hammered but did not break the Union line. The next day,
Bragg continued his assault on the Union line on the left, and in late
morning, Rosecrans was informed that he had a gap in his line. In moving
units to shore up the supposed gap, Rosencrans created one, and James
Longstreet's men promptly exploited it, driving one-third of the Union
army, including Rosecrans himself, from the field. George H. Thomas took
over command and began consolidating forces on Horseshoe Ridge and
Snodgrass Hill. Although the Rebels launched determined assaults on
these forces, they held until after dark. Thomas then led these men from
the field leaving it to the Confederates. The Union retired to
Chattanooga while the Rebels occupied the surrounding heights.