CSS Manassas, formerly the steam icebreaker Enoch Train, was built as a twin-screw towboat at Medford, Massachusetts, by James O. Curtis in 1855. A New Orleans commission merchant, Captain John A. Stevenson, acquired her for use as a privateer after she was captured by another privateer (later gunboat), CSS Ivy; he fitted her out at Algiers, Louisiana as an ironclad ram of a radically modern design. Covered with 1½-inch iron plating (later, draped chain armor was fitted to her port and starboard midsections for additional protection of her vital machinery), her above-water hull was reshaped into a curved "turtle-back" form; at its highest it projected only 4½ feet above the water (not counting her tall smokestacks), when fully loaded. The convex shape of her iron plated and chained topside caused cannon shot to glance off harmlessly. She was 128 feet in length, overall, and had a 26 foot beam and 11 foot draught. She was fitted with an iron ram on her bow, and she also carried a forward-firing cannon behind a single gun port with armored shutter; her iron ram was designed to stave holes in Union vessels. Her low profile made her a difficult target, while her armor protected her against all but the most well-directed Union gunfire. Fast moving, lying low in the water, she looked like a floating cigar or submerged egg shell and was described by Union intelligence as a "hellish machine."
Commissioned as a Confederate privateer on September 12, 1861, Manassas was seized soon afterwards by Flag Officer G. N. Hollins, CSN, for use in the lower Mississippi River. With Lieutenant A. F. Warley, CSN, in command she participated in Flag Officer Hollins' surprise attack on the Federal blockading squadron at Head of Passes, the action being known as the Battle of the Head of Passes, on October 12, 1861. In the action Manassas rammed USS Richmond, but the impact was partly absorbed by a coal barge tied alongside the victim. Manassas, however, suffered the loss of her prow and smokestack and had her engines temporarily thrown out of gear from the impact. She managed to retire under heavy fire from USS Preble and Richmond whose shells glanced off her armor. Two months after this engagement, Manassas was purchased for direct ownership by the Confederate Government.
Under Lieutenant Warley, Manassas joined the force of Captain John K. Mitchell, CSN, commanding Confederate naval forces in the lower Mississippi. She participated in the Battle of Forts Jackson and St. Philip, during which Commodore David Farragut, USN, on his way to New Orleans, ran his fleet past the Confederate forts of Fort Jackson and Fort St. Philip. In the action Manassas attempted to ram USS Pensacola, which turned in time to avoid the blow and deliver a broadside at close range. Manassas then ran into murderous fire from the whole line of the Union fleet. She then charged USS Mississippi and delivered a long glancing blow on her hull, firing her only gun as she rammed. Next she rammed USS Brooklyn, again firing her gun, and injuring her rather deeply, but not enough to be fatal.
After this action Manassas followed the Union fleet quietly for a while, but as she drew closer Mississippi furiously turned on her. Manassas managed to dodge the blow but was run aground. Her crew escaped as Mississippi poured her heavy broadsides into the stranded Confederate vessel. Later Manassas slipped off the bank and drifted down the river in flames past the Union mortar flotilla. Commander David Dixon Porter, USN, in command of the mortar boats, tried to save her as an engineering curiosity, but Manassas exploded and immediately plunged under water.
Years after the war In "Battles and Leaders of the Civil War" there was a claim that a Manassas crewman was knocked off the ironclad by a Union sailor; however the CSS Manassas Captain Lt. A. F. Warley reported no casualties among his crew in an official report of August 13, 1863