[35][36]

Atlanta campaign
For much of its first two years, the 70th Indiana performed reconnaissance duty and guarded railroads in Kentucky and Tennessee. In May 1864, Harrison and his regiment joined General William T. Sherman's Atlanta Campaign in the Army of the Cumberland and moved to the front lines.[37] On January 2, 1864, Harrison was promoted to command the 1st Brigade of the 1st Division of the XX Corps. He commanded the brigade at the battles of Resaca, Cassville, New Hope Church, Lost Mountain, Kennesaw Mountain, Marietta, Peachtree Creek, and Atlanta. When Sherman's main force began its March to the Sea, Harrison's brigade was transferred to the District of Etowah and participated in the Battle of Nashville.[38] While encamped near Nashville, during a particularly cold winter, Harrison prepared coffee and brought it to his freezing men at night; his constant catchphrase as he took lead of his men was: "Come on, boys!"Harrison earned a reputation as a strong leader and as an officer who did not abandon his soldiers in battle.