The 6th Indiana Volunteer Infantry was re-enlisted for three year service from the original regiment at Madison, Indiana, on September 20, 1861, by Colonel Thomas Turpin Crittenden. The regiment subsequently fought in the Battle of Shiloh, the Battle of Stones River, the Battle of Chickamauga, and the Battle of Resaca. At the conclusion of its three-year enlistment, the regiment was mustered out of service on September 22, 1864. Soldiers of the regiment who had unexpired enlistments, and those who re-enlisted were transferred to 68th Indiana Infantry Regiment.