August 29, at the first light, the Third Brigade, First Division, crossed the river in pontoons, and covered the establishment of the pontoon bridge at Caperton's Ferry, Ala. The three succeeding days were occupied in crossing the Second and the remainder of the First Divisions with their trains.
September 2 the advance of this corps debouched from Sand Mountain into Will's Valley, and moved on Winston's Gap in Lookout Mountain. The Third Division crossed the river at Bridgeport and moved on Trenton, Ga.
September 4 the First and Second divisions and Stanley's cavalry command were concentrated at Winston's Gap, and cavalry reconnaissances made down Will's Valley, our Third Division being at Trenton.
September 8 General Davis sent to support an intended reconnaissance of Stanley, and the Third and Second Divisions closed up near Long's Spring.
September 9 news of evacuation of Chattanooga by the enemy and orders to cut off his retreat southward were received; in accordance with which this corps and Stanley's cavalry moved on Alpine, Ga., over Lookout Mountain.
September 11 corps concentrated near Deep Spring at the east side of Lookout Mountain, the cavalry in advance near Alpine, but our trains were parked for safety on the mountain.
September 13 in obedience of orders the corps moved, without wagons, to effect a junction with Thomas' corps at Stevens' Gap, the trains being left with General Lytle, who was temporarily put in command of one brigade of each division detached to protect the trains and our rear.
September 16 Third Division camped in Steven's Gap, Second Division on Lookout Mountain, 12 miles distant, and First Division at the head of Stevens' Gap on the mountain.
September 17 Second Division took position opposite of and observing Dug Gap, First Division near Bailey's Cross-Roads, Third Division at Stevens' Gap.
September 18 corps closed upon Thomas' right, Johnson's division (Second) holding left of our line, Sheridan's division (Third) on the right, Davis' division (First) at the center, Thirty-ninth Indiana (mounted infantry) keeping up connection with cavalry command at Stevens' Gap, Colonel Post's brigade (First Brigade, First Division) at the head of Stevens' Gap, in Lookout Mountain, guarding the trains.
During the night of the 18th and the morning of the 19th the whole army closed up on the extreme left to cover our line of communication with Chattanooga. Trains present with troops, except ammunition trains, ordered to go to Chattanooga by way of Chattanooga Valley road, between Lookout Mountain and Missionary Ridge, our line of march and battle being on the east side of Missionary Ridge. Johnson's and Davis' divisions were ordered at an early hour, immediately on their arrival at Crawfish Spring, to move to the left and report to Major-General Thomas. Major-General Negley was ordered to report for orders to General McCook. General Wood's division held Gordon's Mills, and was on Sheridan's left. Such was the condition of the Twentieth Corps at the opening of the first day's battle of the Chickamauga. General Negley was held in echelon to our right rear near Crawfish Spring. At