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, , 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 corvette in 1857; in early 1859 the Royal Navy started building two iron-hulled 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 unarmored 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.