A small tributary of the Tennessee river, which it joins near Chattanooga, Tennessee, U.S.A. It gives its name to the great battle of Chickamauga in the American Civil War, fought on the 19-20th of September 1863, between the Federal army of the Cumberland under Major-General W. S. Rosecrans and the Confederate army under General Braxton Bragg. For the general operations of Rosecrans' army in 1863 see American Civil War. A successful war of manoeuvre had brought the army of the Cumberland from Murfreesboro to Decherd, Tenn., and Bragg's army lay on the Tennessee at and above Chattanooga. Rosecrans was expected by the enemy to manoeuvre so as to gain touch with the Union forces in the upper Tennessee valley, but he formed an entirely different plan of operations. One part of the army demonstrated in front of Chattanooga, and the main body secretly crossed the river about Stevenson and Bridgeport (September 4th). The country was mountainous, the roads few and poor, and the Federals had to take full supplies of food, forage and ammunition with them, but Rosecrans was an able commander, his troops were in good hands, and he accepted the risks involved. These were intensified by the want of good maps, and, in the event, at one moment the army was placed in a position of great danger. A corps under A. McD. McCook moved south-eastward across the ridges to Alpine, another under Thomas marched via Trenton on McLemore's Cove. The presence of Federal masses in Lookout Valley caused Bragg to abandon Chattanooga at once, and the object of the manoeuvre was thus accomplished; but owing to the want of good maps the Union army was at the same time exposed to great danger. The head of Thomas's column was engaged at Dug Gap, on the 11th, against the flank guard of Bragg's army, and at the time McCook was far away to the south, and Crittenden's corps, which had occupied Chattanooga on the 9th, was also at a distance. Thomas was isolated, but Rosecrans, like every other commander under whom he served, placed unbounded confidence in his tenacity, and if Bragg was wrong in neglecting to attack him on the 14th, subsequent events went far to disarm criticism. By the 18th of September Rosecrans had at last collected his army on Chickamauga Creek covering Chattanooga. But Bragg had now received heavy reinforcements, and lay, concentrated for battle, on the other side of the Creek.
The terrain of the battle of Chickamauga (19th-20th of September) had little influence on its course. Both armies lay in the plain, the two lines roughly parallel. Bragg's intention was to force his attack home on Rosecrans' left wing, thus cutting him off from Chattanooga and throwing him back into the mountain country whence he had come. On the 19th a serious action took place between the Confederate right and Rosecrans' left under Thomas. On the 10th the real battle began. The Confederates, in accordance with Bragg's plans, pressed hard upon Thomas, to whom Rosecrans sent reinforcements. One of the divisions detached from the centre for this purpose was by inadvertence taken out of the first line, and before the gap could be filled the Confederate central attack, led by Longstreet and Hood, the fighting generals of Lee's army, and carried out by veteran troops from the Virginian battlefields, cut the Federal army in two. McCook's army corps, isolated on the Federal right, was speedily routed, and the centre shared its fate. Rosecrans himself was swept off the field in the rout of half of his army. But Thomas was unshaken. He re-formed the left wing in a semicircle, and aided by a few fresh brigades from Rossville, resisted for six hours the efforts of the whole Confederate army. Rosecrans in the meantime was rallying the fugitives far to the rear near Chattanooga itself. The fury of Bragg's assault spent itself uselessly on the heroic divisions under Thomas, who remained on the field till night and then withdrew in good order to Rossville. Here he remained on the 2 ist, imposing respect upon the victors. On the 22nd Rosecrans had re-established order, and Thomas fell back quietly to Chattanooga, whither Bragg slowly pursued. For the subsequent events of the campaign see Chattanooga. The losses in the battle bear witness to a severity in the fighting unusual even in the American Civil War. Of 70,000 Confederates engaged at least 18,000 were killed and wounded, and the Federals lost 16,000 out of about 57,000. The battlefield has been converted into a national park, and was used during the Spanish American War (1898)(1898) as a place of mobilization for the U.S. volunteers.