The 89th Ohio regiment formally mustered into service at Camp Dennison, near Cincinnati, Ohio, on August 1, 1862. The 89th joined the Army of the Cumberland’s advance on Chickamauga, Georgia, where the Battle of Chickamauga erupted on September 19 and 20, 1863. Confederate General Braxton Bragg’s Army of Tennessee attacked the Union’s Army of the Cumberland on September 19. On the next day, the two sides resumed the engagement, with the Northern army retreating from the battlefield the night of September 20. In this fight, the 89th Ohio suffered greatly. At the battle’s conclusion, the regiment only had seventy-five healthy and unharmed men available for duty. An additional forty men were recovering wounds, while twenty more soldiers suffered from various illnesses in Union hospitals.