Marks fought for the Confederacy during the Civil War, and part of his leg was amputated as a result of a wound suffered at the Battle of Stones River in 1862.

[3] He attended school in Owensboro until the age of 14, when his father died, and he focused on helping his mother maintain the family farm.

[2] Although he had little formal education afterward, he was an avid reader, and poured through multiple books on history and ancient literature.

[1] In early 1861, he ran as the pro-Union candidate for his district's representative to the state's proposed convention on secession, and canvassed with his opponent, future governor Peter Turney.

He was elected captain of Company E, 17th Tennessee Infantry, which was initially under the command of Felix K. Zollicoffer, and saw action at the battles of Camp Wildcat (October 1861) and Mill Springs (January 1862) in Kentucky.

Marks's regiment fought at the Battle of Munfordville, where was he chosen by Buckner to accept the formal surrender of Union forces.

[2] Following this invasion, the 17th was assigned to General Patrick Cleburne's division, with which it fought at the Battle of Stones River on December 31, 1862.

As Marks's regiment charged a Union battery during this engagement, his right leg was shattered by canister shot, and was subsequently amputated below the knee.

[2] Marks spent most of the remainder of the war convalescing in Winchester and at a hospital in LaGrange, Georgia,[4] though he later joined General Nathan B. Forrest's staff as a judge advocate.

The committee determined that railroad agents had acted unethically during the Brownlow administration, and had attempted to defraud the state, and thus should only be entitled to partial repayment.

[8] Marks married Novella Davis in 1863, while he was recovering from his injury received at the Battle of Stones River.