During the Antebellum era, he served four terms in the United States House of Representatives, interrupted by a brief stint as ambassador to China.

When the American Civil War broke out, he sided with the Confederacy, becoming a brigadier general in the CS Army and then a Confederate Congressman.

Marshall graduated from the United States Military Academy at West Point, New York, in 1832, was assigned to the mounted rangers, served in the Black Hawk War,[1] and was breveted as a second lieutenant.

In 1836 he raised a company of volunteers and marched to defend the Texas frontier against the Indians, but his force disbanded on hearing of General Sam Houston's victory at San Jacinto.

[1] In 1846 he became Colonel of the 1st Kentucky Cavalry during the Mexican–American War, where he fought at the Battle of Buena Vista as a part of Zachary Taylor's Army of Occupation.

Marshall, a moderate in his political views, supported John C. Breckinridge for president in the Election of 1860 and advocated the commonwealth's neutrality.

Frustrated by his inability to secure a good assignment following his victory at Princeton Court House in present-day West Virginia in May, Marshall briefly resigned his commission in June 1862.

In addition to numerous poems and many magazine articles, she published novels entitled: Eleanor Morton, or Life in Dixie (New York, 1865), Sodom Apples (1866), Fireside Gleanings (Chicago, 1866), As by Fire (New York, 1869), Wearing the Cross (Cincinnati, 1868), Passion, or Bartered and Sold (Louisville, 1876), and A Criminal through Love (1882).