The Ninth went out at first in the three months service, but upon its return re-organized under a three years enlistment. Leaving Indiana in September, 1861, it proceeded to West Virginia, where it remained on duty until February, 1862, fighting in the meanwhile at the battles of Green Brier and Camp Allegheny; in the latter engagement there was some sharp fighting in which the Ninth lost 8 killed, and 13 wounded. In February, 1862, it was ordered to join Buell's Army, where it was assigned to Hazen's Brigade of Nelson's Division, with which it marched to Shiloh; its losses in that battle were 17 killed and 153 wounded. The year 1862 was one of arduous campaigns and long marches, ending, with the year, in Rosecrans's hard-fought battle of Stone's River. The regiment was then in Palmer's (2d) Division, of Crittenden's Corps, its casualties on that field amounting to 11 killed, 87 wounded, and 11 missing. At Chickamauga, it lost 13 killed, 91 wounded, and 22 missing. In October, 1863, the regiment was assigned to Grose's (3d)Brigade, Palmer's (1st) Division, Fourth Corps. During the Atlanta campaign this division was commanded by General Stanley, and by General Kimball in the Franklin-Nashville campaign. The regiment reënlisted in December, 1863, and thus preserved its organization during the war. After the victory over Hood, at Nashville, December 15, 1864, it marched into East Tennessee; from there it moved to Texas, where it remained with the Army of Occupation until September, 1865, when it was mustered out and returned home.