From August 15 to September 5, the regiment was on detached duty in New York during the draft disturbances. On September 24, the unit moved to Bridgeport, Alabama, transferring to the Army of the Cumberland. By October 4, they were guarding the Nashville and Chattanooga Railroad at Elkwater Bridge and Tullahoma, Tennessee. In 1864, the regiment was veteranized at Tullahoma on January 24. They became part of the 2nd Brigade, 1st Division,
XX Corps,
Army of the Cumberland, in April. From May 1 to September 8, the regiment took part in the
Atlanta campaign, engaging in major actions including the
Battle of Rocky Face Ridge (May 8–11), and the
Battle of Resaca (May 14–15), where they lost 68 men while capturing the colonel, colors, and many soldiers of the
38th Alabama Infantry Regiment. The regiment also fought at
New Hope Church (May 25), and participated in the operations along Pumpkin Vine Creek and the
Battle of Dallas (May 28). From June 10 to July 2, they were involved in operations around
Marietta and the assaults against
Kennesaw Mountain, including actions at Pine Hill (June 11–14), Lost Mountain (June 15–17), Gilgal Church (June 15), Muddy Creek (June 17), Noyes Creek (June 19), and
Kolb's Farm (June 22), where Colonel Colgrove was badly wounded and Lieutenant Colonel Fesler assumed command. They continued in the campaign with an assault on Kennesaw Mountain (June 27), and saw action at Ruff's Station (July 4),
Chattahoochee River (July 5–17), and the
Battle of Peachtree Creek (July 19–20). The regiment remained engaged during the
Siege of Atlanta (July 25–August 25), and participated in the operations at Chattahoochee River Bridge (August 26–September 2). They then occupied the city of
Atlanta from September 2 to November 4. The 27th Indiana Infantry Regiment was mustered out of service on November 4, 1864. Remaining veterans and recruits were transferred to the
70th Indiana Infantry Regiment. ==Casualties==