HEADQUARTERS DEPARTMENT OF THE CUMBERLAND,
Murfreesborough, June 21, 1863.

Major General H. W. HALLECK, General-in-Chief:

GENERAL: In your favor of the 12th instant you say you do not see how the maxim of not fighting two great battles at the same time applies to the case of this army and Grant's.

Looking at the matter practically, we and our opposing forces are so widely separated that for Bragg to materially aid Johnston he must abandon our front substantially, and then we can move to our ultimate work with more rapidity and less waste of material on natural obstacles. If Grant is defeated, both forces will come here, and then we ought to be near our base.

The same maxim that forbids, as you take it, a single army fighting two great battles at the same time (by the way, a very awkward thing to do), would forbid this nations' engaging all its forces int he great West at the same time, so as to leave it without a single reserve to stem the current of possible disaster. This is, I think, sustained by high military and political considerations.

We ought to fight here if we have a strong prospect of winning a decisive battle over the opposing force, and upon this ground I shall act. I shall be careful not to risk our last reserve without strong grounds to expect success.

W. S. ROSECRANS,

Major-General.

When General Rosecrans finally determined to advance, he was permitted to select, without restriction, his own line of operations by which to reach Chattanooga, only being directed to connect his left, so far as practicable, with the army of General Burnside, and to report daily by telegraph his movements till he crossed the Tennessee River. General Burnside was also ordered to connect his right as much as possible with General Rosecrans' left; so that if the enemy should concentrate upon either army, the other could move to its assistance.

General Rosecrans on the 25th of June commenced a forward movement upon the enemy, well intrenched at Tullahoma, covered in front by the defiles of Duck River, a deep, narrow stream, with few fords or bridges, and a rough, rocky range of hills, which divides "the barrens" from the lower level of Middle Tennessee. Bragg's main force occupied a strong position north of Duck River from Shelbyville, which was fortified, to Wartrace, all the gaps on the roads leading thereto being held in force.

General Rosecrans determined to render useless the rebel entrenchments by turning their right and moving on their communications at the railroad bridge on Elk River, thus compelling a battle on our won ground, or driving them on a disadvantageous line of retreat. By admirable combined movements he deceived the enemy by a threatened advance in force on their left at Shelbyville, while the mass of his army in reality seized Hoover's, Liberty, and the other gaps by hard fighting, and moved on Manchester, thus turning the right of the enemy's defenses of Duck River and directly threatening Bragg, who was compelled to fall back to Tullahoma, hotly pursued by Granger, who had brilliantly carried Shelbyville on their left. Dispositions were immediately made to turn Tullahoma and fall upon the enemy's rear, but Bragg abandoned to us his intrenched camp and rapidly fell back toward Bridgeport, Ala.

In the words of General Rosecrans' official report:

Thus ended a nine days' campaign, which drove the enemy from two fortified positions and gave us possession of Middle Tennessee, conducted in one of the most extra-ordinary rains ever known in Tennessee at that period of the year, over a soil that became almost a quicksand.

Our operations were retarded thirty-six hours at Hoover's Gap and sixty hours at and in front of Winchester, which alone prevented us from getting possession of his communications and forcing the enemy to a very disastrous battle. These results were far more successful than was anticipated, and could only have been obtained by a surprise as to the direction and force of our movements.