The American Civil War (1861-1865) saw a commitment to naval supremacy as much as one to land warfare. Both sides understood the importance of access to the Atlantic for resupply, medicines and newly-christened warships coming from England. As such, the naval program of the North blossomed considerably as ironclads were laid down as fast as possible. USS Dunderberg became a product of the period, a casemate ironclad ordered on July 3rd, 1862. The contract was given to builder William H. Webb of New York City and her keel laid down around October 3rd, 1862.
The vessel was developed as a deep water warship, one not confined to shoreline work, which gave her some inherent tactical flexibility. Her profile was consistent for ironclads of the time - a low profile superstructure, center-mounted smoke funnel and iron casemate with angled sides to deflect shot away from critical components. The warship displaced 7,060 tons and was given a length of 377.3 feet with a beam of 72.9 feet and a draft of 21 feet. Internally, she carried a crew of about 600 men. Armor protection ranged from 3.5" at the waterline belt to 4.7" at her casemate.
Her installed power consisted of 6 x tubular boilers with 2 x horizontal back-acting steam engines developing 4,000 horsepower to a single shaft. Maximum speed (in ideal conditions) was nearly 15 knots with a range out to 2,200 kilometers. Despite her propulsion scheme, she retained a brigantine sail rigging which technically gave the ship infinite operational ranges - though at much reduced speeds.
Armament centered on 4 x 15" Dahlgren turreted muzzle-loaded main guns and 8 x 11" Dahlgren muzzle-loaded guns in the casemate. A solid oak ram was fitted to her bow as this remained common practice for ironclads of the period.
Despite her keel laid down during the "War of the States", delays in her construction saw to it that she was not made ready in time for service in the bloody American conflict - a shortage of skilled laborers and materials being two reasons cited for her missing the war altogether. Once in service she was notable for being one of the most powerful ironclads in the United States Navy (USN) inventory. As her services were no longer required by the USN, the warship was purchased back by its builder and sold off to France where she began a new career - under the name of "Rochambeau".
France headed off an attempt by Prussia to acquire the ship.
Under new ownership, the vessel was commissioned on August 7th, 1867. Her armament was changed to 4 x 10.8" Mle 1864/66 breech-loaded guns with 10 x 9.4" Mle 1864/66 breech-loaded guns. Her bow section was also revised and she lost her oak ram. The machinery was also addressed for the better. The overhaul occurred during 1868.
Her only claim to fame in French naval service was in North Sea patrolling and the blockading of enemy Prussia during the Franco-Prussian War (1870-1871) - a German victory which led to the fall of the Second French Empire and the rise of the French Third Republic. She was decommissioned and struck from the Naval Register on April 15th, 1872. Her scrapping occurred in 1874.