William S. Rosecrans and his Army of the Cumberland spent the six months following the Battle of Stones River licking their wounds, reorganizing, and resupplying while “Old Rosey” prepared for his offensive south to Chattanooga. From June 24–July 3, Rosecrans’s army out-maneuvered Braxton Bragg’s Army of Tennessee during the Tullahoma Campaign. By mid-September, Chattanooga was in Federal hands, and Union soldiers were spread across south Tennessee, north Alabama, and north Tennessee. All seemed to be coming up aces for William Rosecrans, but Braxton Bragg was determined to put up a fight.
Bragg concentrated his forces in LaFayette, Georgia, and determined to reoccupy the valuable Chattanooga. By September 17, Bragg had been reinforced with the eastern divisions of Maj. Gen. John Bell Hood and the Mississippi division under Brig. Gen. Bushrod Johnson. With renewed confidence that Chattanooga could be recaptured, Bragg marched his army to the west bank of Chickamauga Creek, hoping to position his troops between Chattanooga and the Federal army, cutting off their line of retreat. As Bragg’s infantry crossed the creek on the 18th, they skirmished with Federals. Bragg had been hoping that his advance would be a surprise; Rosecrans, however, had observed the Confederates marching in the morning and anticipated Bragg’s plan. By the time Bragg’s army crossed the creek, Union reinforcements had arrived.
The Battle of Chickamauga began in earnest shortly after dawn on September 19. Throughout the day, Bragg’s men gained ground but could not break the extended Union line despite a series of aggressive attacks. Confederate luck changed when, at 11 p.m., Lt. Gen. James Longstreet’s divisions arrived at Chickamauga, giving the Confederate force superior numbers. Bragg divided his army into two wings: Longstreet commanded the left; Lt. Gen. Leonidas K. Polk took charge of the right. The battle resumed at 9:30 a.m. the next morning, with coordinated Confederate attacks on the Union left flank.
About an hour later, Rosecrans, believing a gap existed in his line, ordered Brig. Gen. Thomas Wood’s division to fill the gap. Wood, however, knew that the order was a mistake; no such gap existed in the Federal line, and moving his division would, in turn, open a large swath in the Union position. However, Wood had already been berated twice in the campaign for not promptly following orders. To avoid further reprimand, he immediately moved, creating a division-wide hole in the Union line. This was the chance that the Confederates needed. Longstreet massed a striking force, led by Hood. Longstreet’s men surged through the gap that Wood had created, and Union resistance at the southern end of the battlefield evaporated as Federal troops, including Rosecrans himself, were driven off the field and back to Chattanooga.
Union Maj. Gen. George H. Thomas, in an action that earned him the nom de guerre “The Rock of Chickamauga,” took command of scattered Federal forces on the field and consolidated them on Horseshoe Ridge and Snodgrass Hill. Thomas and his men formed a defensive position, and although Confederates continued to assault and pressed to within feet of the Union line, the Federals held firm. Thomas withdrew as darkness fell. Bragg’s victorious army followed toward Chattanooga and occupied the heights surrounding the town, blocking Federal supply lines—but they did not pursue Rosecrans further.
While Chickamauga was a decided Confederate victory, the results of the battle were staggering. With more than 16,000 Union and 18,000 Confederate casualties, Chickamauga reached the highest losses of any battle in the Western theater. Although the Confederates had driven Rosecrans from the field, they had not succeeded in Bragg’s goals of destroying Rosecrans’s army or reoccupying Chattanooga. Fighting would resume less than two months later in the battles for Chattanooga.