Learn about this topic in these articles:
Until the 1960s, tank armour consisted of homogeneous steel plates or castings. The thickness of this armour varied from 8 mm on early tanks to 250 mm at the front of the German Jagdtiger of 1945. After World War II, opinions differed about the value of armour protection. Tanks such as the Leopard 1 and AMX-30 had relatively thin armour for the sake of light weight and greater mobility, which...
The use of larger guns with more penetrating power and explosive shells made armour plating imperative. Among early experiments were floating armoured batteries built for the Crimean War. Heavy wrought-iron plates over a thick wooden backing gave these flat-bottomed vessels outstanding protection as they carried large-shell guns close inshore.
Aircraft carriers, at least in the U.S. Navy, have retained armoured flight decks, though in their case the armour provides structural strength as well as limited protection.
...than the shift from sail to steam in the 19th century. The shell gun (raised to naval attention during the Crimean War by the Battle of Sinope, November 30, 1853) compelled navies to adopt the iron sheathing of hulls. This pointed the way to all-metal hulls (iron, then steel), which in turn both permitted and demanded as a response the installation of rifled, breech-loaded guns of major...