Although the benefits of armor on ships were recognized early in the nineteenth century, conservative thinking, ship instability and technical difficulties in iron-working prevented the construction of sea-going ironclads until the late 1850s. When France built La Gloire, the British responded with the Warrior. This three-masted sailing ship was driven in battle by a screw (propeller) and was armed with both smoothbore cannons and more modern rifled naval guns. She had an iron frame and wood planking with iron plates attached to her sides for much of her length.
During the American Civil War the benefits of ironclads were confirmed when C.S.S. Virginia (formerly U.S.S. Merrimac ) decimated a small fleet of wooden steam frigates and was prevented from sinking them all only by the arrival of another ironclad, the U.S.S. Monitor.
Ironclads may be constructed in the shipyard. Although less heavily gunned than a ship of the line, an ironclad may defeat one due to the ironclad’s armor.
