It has already been mentioned that General Rosecrans after winning the battle of Murfreesboro at the beginning of 1863, remained inactive at that place nearly six months, though, of course, constantly busy recruiting his army, gathering supplies, and warding off several troublesome Confederate cavalry raids.  The defeated General Bragg retreated only to Shelbyville, ten miles south of the battle-field he had been obliged to give up, and the military frontier thus divided Tennessee between the contestants.  Against repeated prompting and urging from Washington, Rosecrans continued to find real or imaginary excuses for delay until midsummer, when, as if suddenly awaking from a long lethargy, he made a bold advance and, by a nine days’ campaign of skilful strategy, forced Bragg into a retreat that stopped only at Chattanooga, south of the Tennessee River, which, with the surrounding mountains, made it the strategical center and military key to the heart of Georgia and the South.  This march of Rosecrans, ending the day before the Vicksburg surrender, again gave the Union forces full possession of middle Tennessee down to its southern boundary.

The march completed, and the enemy thus successfully manoeuvered out of the State, Rosecrans once more came to a halt, and made no further movement for six weeks.  The President and General Halleck were already out of patience with Rosecrans for his long previous delay.  Bragg’s retreat to Chattanooga was such a gratifying and encouraging supplement to the victories of Vicksburg and Port Hudson, that they felt the Confederate army should not be allowed to rest, recruit, and fortify the important gateway to the heart of the Southern Confederacy, and early in August sent Rosecrans peremptory orders to advance.  This direction seemed the more opportune and necessary, since Burnside had organized a special Union force in eastern Kentucky, and was about starting on a direct campaign into East Tennessee.

Finally, obeying this explicit injunction, Rosecrans took the initiative in the middle of August by a vigorous southward movement.  Threatening Chattanooga from the north, he marched instead around the left flank of Bragg’s army, boldly crossing the Cumberland Mountains, the Tennessee River, and two mountain ranges beyond.  Bragg, seriously alarmed lest Rosecrans should seize the railroad communications behind him, hastily evacuated Chattanooga, but not with the intention of flight, as Rosecrans erroneously believed and reported.  When, on September 9, the left of Rosecrans’s army marched into Chattanooga without firing a shot, the Union detachments were so widely scattered in separating mountain valleys, in pursuit of Bragg’s imaginary retreat, that Bragg believed he saw his chance to crush them in detail before they could unite.