Bragg's plan of battle was to fall upon the Federal left, crush it, bend back the line, and place himself between the Federal army and its base. There could have been no better plan of battle formed, but it was not executed in the best fashion possible. Had Bragg fully realized the superiority of Longstreet to his other corps commanders, and still more the superiority of Longstreet's men who had fought at Fredericksburg, Chancellorsville, Antietam and Gettysburg, he would have placed Longstreet upon his right, in order that the blow might be delivered with all that was possible of crushing force. Instead of that he assigned the force of General Leonidas Polk to that position. Polk was a West Point graduate, but soon after graduation he had become a clergyman of the Episcopal church, and for many years past had been a bishop in that church. A fact that had more importance perhaps, was that Polk's men had not been trained by the experience of Lee's tremendous onslaughts to the best work of the soldier, and unfortunately for Bragg, but fortunately for Rosecrans, that left wing of the Federal army upon which the main assault was made, was under command of General George H. Thomas, one of the most determined fighters on either side during the war.

Under Polk the assault was made loosely, and without that perfect concert of action which Longstreet, had he been in command, would have brought to bear. Thomas met it with obstinate resistance, and when opportunity offered, with counter attacks that greatly interfered with Bragg's plans. Nevertheless, the fighting was obstinate and destructive to both sides. In the end Polk succeeded in forcing Thomas's line backwards for a time, but before nightfall the Federal general had recovered the greater part of his ground, and when the first day's fighting ended the position of the two armies was practically the same that had existed in the morning.

About eleven o'clock on the next morning the battle was resumed with fury. Polk again assailed Thomas, and Thomas urgently asked for reinforcements with which to repel the assault. On that part of the line the struggle continued for hours with varying and not unequal success, the advantage lying on the whole with the Confederates. But later in the day Longstreet, who commanded the right center of Bragg's line, made a tremendous assault of that kind which had been rendered familiar to the fighters in Virginia by repeated experience. He swept everything before him. He made a gap in Rosecrans's line crushing its center, separating its wings from each other and driving it into confused retreat. Thomas alone held his force together, and fought the matter out to a finish. In spite of the fact clearly apparent to him that Rosecrans was defeated, and three fifths of his army destroyed, Thomas continued the bloody contest with a fury that knew no flinching, and hesitated at nothing of human sacrifice in the achievement of its purposes. But for Thomas's obstinacy, skill and courage the Federal defeat at Chickamauga would have been a repetition of the disaster at Chancellorsville.

During the night Thomas succeeded in withdrawing his command, and the Federal army fell back to Chattanooga, taking refuge behind the fortifications there. Each army had lost in this struggle from 15,000 to 20,000 men. The exact figures are nowhere procurable.

Bragg had won a great victory, but he had not succeeded in regaining possession of Chattanooga. His enemy held that strong, strategic position. It was therefore his next task to besiege the foe there, and either by fighting or by maneuvering to drive him out of the place.

Two mountain heights, the one known as Lookout mountain and the other as Missionary Ridge, overlook the town, and command many of its approaches. When the battle was over Bragg promptly advanced and seized upon these heights. By doing so he succeeded in placing Chattanooga in a state of siege, stopping the navigation of the river, and cutting off all of Rosecrans's communications, with the exception of one highly inadequate mud road.

It is a maxim of military science that the army which can besiege a position can always capture it in the end unless the beleaguered place is relieved from the outside. Chattanooga was relieved from the outside in an exceedingly quiet, but exceedingly effective way. Ulysses S. Grant—at last a major general in the regular army and in full command of the western department—went thither to supersede Rosecrans in command. The coming of this one silent and unostentatious man meant more to the Federal forces in that quarter than the arrival of half a dozen army corps would have signified. Grant got to Chattanooga on the twenty-third of October, 1863, and set to work at once with his practical common sense to meet and solve the problems of the situation.

He found the army half starved for lack of routes of communication with its bases of supply. He instantly set his men at work to open a new road which the facetious soldiers named the "cracker line," and which connected Chattanooga with a point on the river to which steamboats could come with abundant supplies. This relieved the Federal army in Chattanooga of its condition as an army in a state of siege. It made of it instead an army in the field, well fed, properly supplied, and ready for march or battle, as its commander might direct.

Having thus relieved the distresses of the army he had been sent to command, Grant's next thought was to employ that army in some profitable way. The Confederates, strongly fortified, held Lookout mountain and Missionary Ridge, and stretched their line for twelve miles across the Chattanooga valley. Grant decided to dislodge them. He could not do so with the forces assembled at Chattanooga, but at last the authorities at Washington had recognized him as a man worthy to command, and had placed the entire department under his control, and all its armies were at his disposal. Grant believed in Sherman, and mightily trusted him. At every point in his career where Sherman could be called to his aid Grant summoned that commander, and employed his genius as the most effective instrument for the accomplishment of his own purposes. It is not too much to say that Sherman was to Grant quite all that Stonewall Jackson was to Lee—a lieutenant to whom he might assign the most difficult enterprises with full assurance that they would be executed with all the skill, determination, valor and sagacity that it was possible to bring to bear upon them as military operations.

So when Grant determined to dislodge the Confederates from Lookout mountain and Missionary Ridge his first step was to summon Sherman to join him with the corps then under Sherman's command.