Battle Of Chickamauga, fought upon Chick-amauga creek, an affluent of the Tennessee river, 12 m. S. W. of Chattanooga, in S. Tennessee, Sept. 19, 20, 1863, between the Union army of the Cumberland, under Gen. Rose-crans, and the confederates under Gen. Bragg. During the summer Rosecrans had moved into southern Tennessee, and on Sept. 9 had taken possession of Chattanooga, from which Bragg had retired on his approach. Rosecrans, supposing that the enemy were in full retreat in Georgia, moved after them; but Bragg, having received large reinforcements, and knowing that Longstreet's division from Virginia was on its way to him, resolved to give battle, with the special purpose of recovering Chattanooga. Both armies were considerably scattered in that mountainous region; but on the 18th the forces on both sides were concentrated on the Chick-amauga creek. The main battle was opened on the morning of the 19th, the immediate object of the confederates being to gain possession of the road leading to Chattanooga. The fighting was hot all day, but at its close neither side had gained any decided advantage.

During the night Longstreet arrived with a portion of his division, and was appointed to the immediate command on the confederate left, that on the right being given to Polk. Thomas, who commanded on the Union left, was first attacked by Polk, who was repulsed. But in the mean time Longstreet had been more successful, and was hardly pressing the Union right and centre, where Rosecrans commanded in person. Owing to an erroneous order from Rosecrans to Gen. T. J. Wood, a movement was made which left a wide gap in the Union centre. The confederates poured through this, and routed part of Crittenden's and all of McOook's army corps, driving them from the field in utter confusion. Rosecrans, who had fled to Chattanooga, telegraphed to Washington that his whole army was beaten. But on the left Thomas still held his own. He had taken up a strong line, and awaited the coming attack from the whole confederate force. Long-street, who actually directed the battle, now pressed the whole confederate strength against Thomas, who was outnumbered more than two to one. Assault after assault was made, but each was repulsed; and at half past 5 the attack was abandoned.

Thomas then fell back to Rossville; and during the night of the 21st the whole of his command returned to Chattanooga. This battle was a formal victory for the confederates, who retained the battle field, and captured 40 or 50 guns and some thousands of prisoners, mainly wounded. They however gained no real advantage, for Rosecrans still retained Chattanooga, the prize for which the action was fought. The confederate force actually engaged was about 50,000; the Union force was about 55,000, but of this more than 10,000 were isolated early in the day, and took no further part in the battle. In this estimate the cavalry on either side are not included, as they had no scope for action. The Union loss is officially stated at 1,044 killed, 9,262 wounded, and 4,945 prisoners; 15,851 in all. The confederate reports are wanting for about one third of the force, including Longstreet's own brigades, which were most severely engaged. In the two thirds reported, the loss was 1,394 killed, 8,974 wounded, and 882 missing, 11,250 in all; the entire loss being not far from 18,000. A month after this battle Rosecrans was relieved from the command of the army of the Cumberland, which was incorporated with the armies of the Ohio and the Tennessee, and placed under command of Gen. Grant, who on Nov. 23-25, 1863, defeated Gen. Bragg in front of Chattanooga. (See Chattanooga.)