[1] William Barksdale, a US Congressman and prominent "Fire-eater" was elected as colonel, leading him to resign his commission as brigadier general in Mississippi's state armed forces.

Upon arrival, the Regiment was immediately sent to the battlefield, taking part in the First Battle of Bull Run under the brigade of General Jubal A.

In Tennessee, the 13th fought at the Siege of Knoxville, where they took part in the bloody assault on Fort Sanders on November 29, where Col. McElroy of the 13th was killed.

[1] The Union officer defending the fort, Captain Orlando Metcalfe Poe, reported the capture of the 13th Mississippi's regimental flag, and said "In spite of the gallantry and persistency of the attack, it was handsomely repulsed, with a loss to the enemy of almost the entire which led the assault....I know of no instance in history where a storming party was so nearly annihilated.

[1] The Regiment was sent to assist General Jubal Early's campaign in the Shenandoah Valley, fighting at the Battle of Cedar Creek.