With
Tennessee's
Ordinance of Secession and the outbreak of the Civil War, Smith enlisted in the Confederate Army in the
20th Tennessee Infantry Regiment and was elected a second lieutenant. He first saw combat action at the
Battle of Mill Springs in January 1862, and in April of that same year participated in the
Battle of Shiloh. Later in the year, after being promoted to
colonel of the 20th Tennessee and assigned command of a small
brigade, he was part of the Confederate forces that unsuccessfully tried to seize the
Union post at
Baton Rouge, Louisiana. Confederate Army commander
John C. Breckinridge remarked in his official report that Smith "moved against the enemy in fine style." At the end of the year, he fought in the
Battle of Stones River, where he suffered a serious wound that put him out of action for much of 1863. After his recuperation, Smith resumed field duties, but was again wounded at the
Battle of Chickamauga in September. After another lengthy recovery period, he returned to action during the 1864
Atlanta campaign. He was promoted to brigadier general on July 29, 1864, and commanded an infantry brigade (
Tyler's Tennessee Brigade), assigned to Bates Division,
Hardee's Army Corps in the
Army of Tennessee comprising the 2nd, 10th, and 20th Tennessee, the 37th Georgia, the 30th,
37th, and 50th Tennessee, consolidated, and the 4th Georgia
battalion of
sharpshooters. His first action as a general officer on the extreme left of the Confederate flank at the
Battle of Utoy Creek, he personally led his brigade in a charge against attacking Union soldiers capturing some 30 Union soldiers and the colors of the
8th Tennessee Infantry and
112th Illinois Infantry. The unit was cited in the
OR by his corps commander, Lieut. Gen.
Stephen D. Lee, to whom Bates Division was attached for duty. Smith led his brigade in an assault at the
Battle of Jonesborough, however the terrific fire from the Federal entrenched troops, required them to withdraw to a gully for protection during the assault on August 30, 1864 and they were unable to dislodge the Federal
Army of the Tennessee. His military career ended at the
Battle of Nashville on December 16. Smith surrendered during the battle. After Smith had surrendered and been disarmed, Union Colonel
William L. McMillen, whose brigade had suffered heavily in an engagement with Smith's Brigade, reportedly berated and then attacked the Confederate general, now a disarmed prisoner, with Smith's own sword (one source says "wantonly and repeatedly" Confederate General
William B. Bate in his report stated, "General T. B. Smith, commanding Tyler's brigade, and
Finley's, bore themselves with heroic courage both through good and evil fortune, always executing orders with zeal and alacrity, and bearing themselves in the face of the enemy as became reputations which each had heretofore bravely won." Held at
Johnson's Island in
Ohio and later at
Fort Warren in
Massachusetts, Smith was not released until July 24, 1865. ==Post-war==