While Lee was fighting his tremendous campaigns in Virginia, Maryland and Pennsylvania, and while Grant was battling for Vicksburg, two other armies confronted each other near the southern border line of Tennessee. Rosecrans had command of the Federal forces near Murfreesboro, and Braxton Bragg was in charge of the Confederates at Chattanooga. The position of each of these armies was a serious threat to the other side. If Bragg should be left unoccupied by his enemy it was easily within his power to make a dangerous dash towards Cincinnati or Louisville, while if he should withdraw from Rosecrans's front there was nothing to prevent that general from "marching through Georgia," to Mobile or Savannah or Charleston.
Grant, besieging Vicksburg, asked for reinforcements from Rosecrans by way of warding off that blow in the rear which he feared that Johnston might deliver and at the same time Johnston begged for reinforcements from Bragg in order that he might deliver such a blow. Each of the commanders at Murfreesboro and Chattanooga realized the necessity of remaining where he was so long at least as his adversary should remain. The result was that neither sent the reinforcements for which his brother in the field was so clamorously calling.
These two armies for a long time stood watching each other, each waiting for the other to make some movement that would give it opportunity. In the meanwhile the cavalry on either side was engaged in making some of the most picturesque raids that were at any time made during the struggle. On both sides the cavalry had by this time learned its business, and realized its possibilities of independent action in the enemy's country. The Federal cavalier, Grierson, swept through Mississippi carrying desolation wherever he went. The Confederates, Wheeler and Forrest, rushed hurricanelike through the country north, battling here and there with such forces as they met. Gordon Granger and Colonel Streight on the Federal side were swinging swords almost continually.
The operations of this kind were too many, and strategically of too little importance to call for detailed description in a general history of the war. But two of them were so dramatic in their conduct and ending that they must be mentioned here. One of these was the attempt of Colonel Streight with about 2,000 men to march around Bragg's army, and cut off his communications. This raid was made early in April, and Forrest followed it with all the vigor that usually characterized that general's operations. The two forces were in constant battle as the one swept onward and the other followed. Streight meanwhile was working havoc with Confederate depots of supplies, with railroad property, and other possessions of his enemy. Finally on the third of May, Forrest succeeded in placing himself in a position where he was justified in demanding the surrender of Streight's force. He made the demand boldly and threateningly and Streight surrendered only to learn after the capitulation was made that the men under his command really outnumbered those of Forrest. It was Forrest's boast afterward that in this case he had "won by a pure bluff."
The other raid which rises into historical importance was that of John Morgan north of the Ohio. Starting in July with a force of 3,000 Confederate cavalrymen and ten guns Morgan crossed the Ohio river into Indiana, capturing two steamers and using them as ferryboats. He then swept through Indiana towards Cincinnati, burning mills and bridges, tearing up railroads, and spreading terror in his pathway. But resolution accompanied the terror. Every man in all that region who could bear a gun turned out to fight the raiders and to destroy them before they should succeed in recrossing the river. This was accomplished at last with the aid of gunboats and steamboats. Morgan was compelled to surrender a small remnant of his force, and was sent for safe-keeping to the Ohio state prison, from which he later escaped by digging.
All these operations, of course, were subsidiary to the general purposes of the campaign.
Rosecrans was an exceedingly capable strategist and upon this occasion, more conspicuously than on any other during his career, his capacity in that way was demonstrated.
Bragg occupied Chattanooga, the strategic importance of which has been explained in an earlier chapter. The position was practically impregnable by any form of direct assault; for Rosecrans to have hurled his army against it would have been an act of well-nigh suicidal folly. In such an assault he must have lost ten men for every one of his enemy's men whom he could hope to put hors de combat. Yet it was necessary for Rosecrans to get Bragg out of Chattanooga. In order to do so he pushed a part of his army southward, threatening an invasion of Georgia. That state was defenseless except in so far as Bragg's army defended it. Rosecrans's movement, therefore, quickly compelled Bragg to withdraw from his strong and threatening position in order to head off what he supposed to be that southward movement that Sherman afterward made, and that is known in history as "the march to the sea." As soon as he quitted Chattanooga, Rosecrans occupied that place about the middle of September.
It was apparently good policy for Rosecrans instantly and aggressively to follow his foe, and he did so in spite of the fact that his three corps were dangerously separated at a time of heavy rains, when the roads were bad, streams out of their banks, marching difficult, and promptitude of movement impossible. In the meantime Bragg had been heavily reinforced by Longstreet's corps sent out by Lee to save this situation. Thus strengthened Bragg turned about with intent to assail his adversary, and perhaps to destroy him. On the nineteenth of September the two armies met on the banks of Chickamauga creek. There for two days raged one of the great battles of the war.
Rosecrans brought into the action about 55,000 men and Bragg had perhaps 10,000 more. It was Bragg who made the attack. As the lines lay, the Confederate right and the Federal left extended toward Chattanooga.