Short answers, pulled from the story.
The Army of Tennessee was a Confederate States Army field force that fought in the Western Theater of the American Civil War. It formed in Tennessee in 1862 and fought until its surrender in North Carolina in 1865.
The Army of Tennessee was formed on the 20th of November 1862, when General Braxton Bragg renamed the former Army of Mississippi and divided it into two corps under Leonidas Polk and William J. Hardee.
Braxton Bragg commanded the Army of Tennessee from its formation in 1862 until December 1863, when Joseph Johnston took over. John Bell Hood led the army from July 1864, and Johnston returned to command in early 1865.
The Army of Tennessee fought the Battle of Stones River, the Chickamauga Campaign, the Battles of Chattanooga, the Atlanta campaign, the Franklin-Nashville Campaign, and the Carolinas campaign, including the Battle of Bentonville.
The Army of Tennessee retreated from Nashville after Union troops under George H. Thomas broke through its lines on December 15-16, 1864, routing Cheatham's and Stewart's corps. John Bell Hood judged the army's condition too poor to continue and abandoned Tennessee.
The Army of Tennessee surrendered on the 26th of April 1865, when Joseph Johnston and William T. Sherman signed terms at the Bennett Place near Durham Station, North Carolina. The surrender covered almost 90,000 Confederate troops across several states.