From the date of its organization, in September, 1861, until May, 1862, four companies of the regiment did duty along the Missouri border, in Southern Kansas; others formed part of the post garrisons at Forts Leavenworth, Riley, Kearney, and Laramie. Early in May five companies were ordered to Corinth, Mississippi, and proceeding to Columbus, Kentucky, by steamer, they marched thence along the line of the Mobile & Ohio Railroad to Corinth. After a service of two months in that army, the Division to which the Eighth was attached was ordered to reinforce General Buell. By rapid marches through Eastport, Mississippi, and Florence, Alabama, it joined the “Army of the Ohio” at Murfreesboro, Tennessee, and took part in the extraordinary campaign which ended at Louisville, Kentucky. Thence it moved southward again, with the command to which it was attached, through Perryville and Lancaster to Crab Orchard, and thence to Nashville. There it remained nearly six months, doing provost duty, and there, in February and March, 1863, the five companies left in Kansas joined headquarters, and for the first time in its history the regiment was united. Early in June, 1863, the Eighth rejoined its Division at Murfreesboro. It participated, during that summer, in the campaign against Tullahoma, and, late in August, forming the advance guard of the Twentieth Corps, crossed the Tennessee river at Caperton’s ferry, in pontoon boats. It took an active part in all the movements of the campaign which followed, ending with the battle of Chicamauga and the siege of Chattanooga. On the 23d of November, covering the front of its brigade as skirmishers, the Eighth captured Orchard Knob, the headquarters of Generals Grant and Thomas during the battles of the succeeding two days. On the 25th it participated in the storming of Mission Ridge, and its flag was one of the first, if not the first, planted on the summit. Two days later the Eighth marched, with its corps, to the relief of Burnside, at Knoxville; took part in all the movements of that dreadful winter campaign, and formed a portion of the rear guard on the retreat from Dandridge. Early in January, 1864, at Strawberry Plains, East Tennessee, four-fifths of all the members of the Eighth then present reënlisted as veterans. Returning home in February, the regiment received a furlough for thirty days. Reassembling at this Post, early in April, it returned to the South, and took part in the campaign against Atlanta. Thence, with its corps, it moved back to Nashville, and participated in the battle which ground the Rebel army of the West to atoms. During the first six months of the year 1865, the Eighth was stationed at various points in Alabama and Tennessee, but late in July it was ordered to Texas, where it remained until the 29th of November, when it was mustered out, and ordered home for final discharge. It reached Fort Leavenworth on the 6th of January, 1866, and on the 9th was formally disbanded.