: an armored naval vessel especially of the mid to late 19th century
First Known Use of IRONCLAD
French ironclad Gloire, engraving by Smythe after a painting by A.W. Weedon—Courtesy of the trustees of the British Museum; photograph, J.R. Freeman & Co. Ltd.
Type of warship developed in Europe and the U.S. in the mid-19th century, characterized by the iron armour that protected the hull. In the Crimean War (1853–56) the French and British successfully attacked Russian fortifications with floating batteries, ironclad barges mounting heavy guns. In 1859 the French completed the first iron warship, the Gloire; its iron plates, 4.5 in. (11 cm) thick, were backed by heavy timber. Britain and the U.S. soon followed. Union forces launched armored gunboats on the Mississippi at the start of the American Civil War, and a flotilla captured Fort Henry (1862). The first battle between ironclads was the Battle of the Monitor and Merrimack (1862). Later refinements led to the battleship. See alsomonitor.