In 1592—1598 the First Armour-Plated Ships were Successfully Used.
Built in Korea, the ships successfully repelled a few attacks of the Japanese military fleet. The first in history armour-plates ships, Korean "Kobukson", had the hull shaped up like a raft with two masts (with rectangular sails) and 9-10 oars on each board. The whole hull was protected by a turtle-like shell plated with steel plates that had sharp thorns. The shell had 14 holes for bronze 190 mm cannons. Historians still do not know how they managed to make such strong steel plates that stood Japanese cannon-balls. The steel thorns made boarding impossible. Even in 300 years during the Civil War in the US the southerners could not make same strong steel plates. To protect their ships they had to use armour consisting of many layers of flattened rails.