At the Battle of Shiloh on 7 April 1862, the 15th Infantry was the first new infantry regiment to engage in battle in the Civil War. In April–May 1862, the regiment marched toward and fought in the First Battle of Corinth, Mississippi. By the end of the Civil War, the regiment had fought in 22 major engagements, including Murfreesboro, Chickamauga, Chattanooga, and Atlanta as a part of Brigadier General John H. King's Brigade under Gen. Richard Johnson's Division, XIV Army Corps of the Army of the Cumberland. The regiment was a key element of the only regular brigade in Sherman's Army. The regiment's crest includes the acorn, the symbol of the Major General George Thomas's XIV Corps, and the mountains of stone to symbolize the corps' firm stand as the "Rock of Chickamauga". The four acorns represent the four major engagements.