Although Bragg occupied this advanced position, General Rosecrans was certain that should the Confederate be unable to hold Shelbyville and the surrounding territory, he would retreat to his stronger intrenchments at Tullahoma. This town, situated on the rocky bank of Duck River and surrounded by mountainous passes, was an ideal stronghold. Once the Southern forces should retreat to it, to follow them would be extremely hazardous, for the Confederates could easily command the river and every defile, and pour in a hot fire without permitting the Union troops to get a shot in return. Under these circumstances, General Rosecrans determined, if possible, to cut off the Confederate's chances of retreating to Tullahoma, or, at least, of retreating by the direct way. To do this, he determined to turn the enemy's right, and then make a dash for the railroad bridge at Elk River. Once he had turned the enemy's right and gained the bridge, Bragg, if he retreated, would have to go to Tullahoma by side roads, where both armies would have an equal chance in fighting, so far as the lay of the land was concerned. In all military operations, one of the main elements of success lies in the fact of keeping the other fellow guessing what you are going to do until you do it; and, in order to blind General Bragg as to his real intention, General Rosecrans started in by making an attack on the Confederate centre, as though he intended to push through at that point if he could. While this was going on he hurried his main divisions around to the enemy's right. The army numbered many thousands of infantry, cavalry, and artillery; the battle-ground extended over many miles of territory; and to get every regiment in its proper place was no light task. Messages flew hither and thither, carried by telegraph and by horseback messengers, and many a detail was completed only to be totally altered at the last moment. And while this was going on, a close watch had to be kept on the enemy, for fear he would make some movement never dreamed of by our troops. After months of preparation and numerous small conflicts, the army began to move on the 23d of June, 1863. It was divided into three corps, the right under McCook, the centre under Thomas, and the left under Crittenden. The weather was by no means favorable; and soon it was raining in torrents, rendering the roads a mass of liquid mud, and swelling even the smaller streams to such an extent that they could scarcely be forded. In a campaign lasting nine days, General Rosecrans declares that their advance was delayed ninety hours by the elements.