Organized at Camp Joe Holt, Indiana, September 9, 1861, and crossing into Kentucky, soon after, it commenced its active service in Rousseau's Brigade, McCook's Division. In March, 1862, it marched with Buell's Army to re-enforce Grant, arriving on the field of Shiloh in time to take part in the battle and change a defeat into a victory. The Fifth was actively engaged there, losing 7 killed and 56 wounded. After participat ing next in the Siege of Corinth, it moved with Buell's troops on their long and arduous campaigns, the next battle of the regiment occurring at Stone's River, Tenn., on December 31, 1862. It was then in Baldwin's (3d) Brigade, Johnson's (2d) Division, McCook's Corps; its loss in that engagement was 19 killed, 80 wounded, and 26 missing, out of 320 engaged, a part of the regiment being on detached service. The Fifth suffered its severest loss at Chickamauga, its casualties on that field amounting to 14 killed, 79 wounded, and 32 missing, out of a small number engaged; Major Charles L. Thomassen was killed in this battle. In October, 1863, the regiment became a part of Hazen's (2d) Brigade, Wood's (3d) Division, Fourth Corps, in which command it fought at Missionary Ridge and through the Atlanta campaign of 1864. Though small in numbers, it made a brilliant fight at Orchard Knob and Missionary Ridge, its percentage of loss being again very large; in fact, the total percentage of loss in action of the Fifth Kentucky, as based on its total enrollment, was exceeded by but few regiments in the entire army. The regiment was mustered out September 14, 1864.