Iron armour

Iron armour was a type of armour used on warships and, to a limited degree, fortifications. The use of iron gave rise to the term ironclad as a reference to a ship 'clad' in iron. The earliest material available in sufficient quantities for armouring ships was iron, wrought or cast. While cast iron has never been used for naval armour, it did find a use in land fortifications, presumable due to the lower cost of the material. One well known example of cast-iron armour for land use is the Gruson turret, first tested by the Prussian government in 1868. Armoured ships may have been built as early as 1203, in the far east. In the West, they first become common when France launched the first ocean-going ironclad La Gloire in 1859. The British Navy responded with HMS Warrior in 1860, triggering a naval arms race with bigger, more heavily armed and armoured ironclads.

Early experiments showed that wrought iron was superior to cast iron, and wrought iron was subsequently adopted for naval use. British efforts at perfecting iron armour were headed by a government Special Committee on Iron, formed in 1861 by War Secretary Lord Herbert for the continued research into naval armour. Among its members was Sir William Fairbairn, a noted civil and structural engineer who had also built over 80 iron vessels before retiring from shipbuilding. Other members included metallurgist John Percy, civil engineer William Pole and representatives of the Royal Engineers, Royal Artillery and Royal Navy. This committee worked four years, between 1861 and 1865, during which time it formulated the best performing armor with the metallurgy as then known, suggested ways for improving its production and quality and helped develop more effective shot against ironclad vessels.