[4][5] The force at Humboldt was to hold the Mobile and Ohio Railroad from Trenton to Jackson, Tennessee, and guard the ordnance, commissary and quartermaster's supplies stored at that place.

[4] This service was performed until 18 December, when the regiment moved to Jackson to aid in defense of that place against an impending attack thereon by heavy forces of cavalry under lieutenant general Nathan Bedford Forrest.

[4] Thence moved to Trenton on the 23d of December, and the same night marched in obedience to orders to a point near Humboldt, to protect a force repairing Mobile and Ohio Railroad, which had just been destroyed by rebel cavalry.

During the time that the regiment had been about Jackson, the rebel cavalry under Forrest had captured the hospital at Trenton, and had made prisoners of the sick and the guards on duty at Trenton, by which the One Hundred and Twenty-second for the time being lost Major James F. Chapman and Captain B. Cowan, W. W. Freeman, Regimental Quartermaster, and 60 enlisted men taken prisoner.

The fight continued till about 2 o’clock P.M., when the enemy fell back leaving the field in possession of the little force that had fought them for nearly three hours, and had during that time captured eight pieces of artillery and 500 prisoners, among them Major Strange, Forrest's Adjutant General.

During the ensuing months till 30 October 1863, the men were constantly on duty and often engaged in skirmishes with cavalry forces of the enemy threatening the railroad.

The regiment remained at Eastport till 8 December 1863, when it moved to Paducah, Kentucky, and thence on 19 January 1864, to Cairo, Illinois, Colonel Rinaker being assigned to the command of the post.

On 24 March 1864, a considerable rebel force under Forrest attacked Paducah, and three companies of the One Hundred and Twenty-second, E, H and K, took part in the defense, and aided in repelling the enemy in the three several assaults they made on Fort Anderson at that place.

[4] 26 June 1864, the regiment after the defeat of Sturgis at Guntown, Mississippi, was ordered to join the command of General A. J. Smith, then at LaGrange, Tennessee.

As the enemy advanced across the open plain, covered by a heavy artillery fire, the One Hundred and Twenty-second and the rest of the Brigade moved forward from the opposite side, and met the enemy just at the crest of the ridge, and opened a destructive fire upon them with such effect that their ranks were shattered and the whole force driven back with heavy loss in men and officers.

[4] Again on 4 August the regiment marched from Memphis, with the rest of General Smith's command, for Holly Springs, where after being detained a few days, the force moved on to Oxford, Mississippi.

The weather was much of the time during the march, cold, and the ground rough and frozen, the shoes of the men worn out and much severe suffering was endured.

[4] On 6 March the One Hundred and Twenty-second Regiment with the One Hundred and Nineteenth Illinois, Twenty-first Missouri Infantry, Eighty-ninth Indiana, constituting First Brigade, Second Division, XVI Army Corps, and Fifty-eighth Illinois, under command of Colonel Rinaker, went by ocean steamer to Dauphin Island, Alabama, near mouth of Mobile Bay.

On the 23d of March, moved thence with the rest of the XVI Corps to assist in the investment of rebel fortifications at Blakely and Spanish Fort, these constituting the eastern defenses of Mobile.

And on 9 April 1865, it occupied the center of the line formed by the First Brigade, General Garrard's Division, XVI Corps of the Army of the Tennessee, in the assault upon the rebel works at Blakely, and materially aided in capturing that place.

On 5 June, the regiment returned to Mobile, Alabama, and on 15 July it was mustered out, and proceeded thence to Springfield, Illinois, where it was paid off and finally discharged at Camp Butler on 4 August 1865.