 An ironclad is a steam @-@ propelled warship protected by iron or steel armor plates used in the early part of the second half of the 19th century . The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells . The first ironclad battleship , Gloire , was launched by the French Navy in November 1859 . The British Admiralty had been considering armored warships since 1856 and prepared a draft design for an armored <unk> in 1857 ; in early 1859 the Royal Navy started building two iron @-@ <unk> armored frigates , and by 1861 had made the decision to move to an all @-@ armored battle fleet . After the first clashes of ironclads ( both with wooden ships and with one another ) took place in 1862 during the American Civil War , it became clear that the ironclad had replaced the <unk> ship of the line as the most powerful warship afloat . This type of ship would come to be very successful in the American Civil War . 
