Early in the Civil War began, Sherman served as lieutenant colonel of the 56th Illinois Volunteer Infantry Regiment and major of the 12th Regiment Illinois Volunteer Cavalry without seeing any significant action. On September 4, 1862 he was appointed colonel of the 88th Illinois Volunteer Infantry Regiment (a.k.a. 2nd Board of Trade Regiment). Sherman led his regiment at the battles of Perryville and Stones River. He was not with the army during the battle of Chickamauga but took command of a brigade shortly after the battle. His brigade became the 1st Brigade in Philip H. Sheridan's 2nd Division of the newly formed IV Corps. Sherman was one of the brigade commanders that made the charge up Missionary Ridge during the battle of Chattanooga. He continued leading his brigade during the early part of the Atlanta Campaign at Rocky Face Ridge and Resaca before he was appointed as the chief of staff to the IV Corps. He served in that capacity during the rest of the campaign until he was captured outside Atlanta on July 7, 1864. He was officially exchanged on October 7, 1864 and was assigned to the Army of the Potomac as the assistant inspector general of the Cavalry Corps during the Appomattox Campaign. Sherman was brevetted to brigadier general on March 13, 1865 and received a full promotion to brigadier general of volunteers on July 21, 1865. He was mustered out of the volunteer services on January 15, 1866.