In 1861, Forrest enlisted as a private in the Tennessee cavalry. As a lieutenant colonel, he defended Fort Donaldson, after which he was promoted to colonel of 3rd Tennessee Cavalry at Battle of Shiloh. In June 1862, he led a raid into west Tennessee, during which time, he captured the garrison at Murfreesboro. In the next month, he received the rank of brigadier general. Initially, he took part in joint operations during the Chattanooga campaign until conflict with General Braxton Bragg led him to receive his own independent command. In December 1863, he received another promotion to major general. In April 1864, he captured Fort Pillow. Subsequently, he led his force into battle at Brices' Crossroads, and later, at Tupelo. In late 1864, he served in the Tennessee campaign before his received his last promotion - to lieutenant general. In April 1865, he was finally captured in Battle at Selma, Alabama.