The Army of Tennessee was the principal Confederate army operating between the Appalachian Mountains and the Mississippi River during the American Civil War. It was formed in late 1862 and fought until the end of the war in 1865, participating in most of the significant battles in the Western Theater. It should not be confused with the Union Army of the Tennessee, named after the Tennessee River. Many Army of Tennessee personnel, including General Simon B. Buckner, were Kentuckians who defected southward after their state remained in the Union.