What did the ironclads do?

Answer 1

Basically, an "ironclad" was a steam-propelled warship fitted with plates of iron armor. The idea of an armored warship was not new; the Vikings used to line the sides of their longships with their shields, several shipbuilders came up with the idea of a ship encased in lead, and, most famously, the Koreans built a "turtle" ship in the sixteenth century, armored with iron and propelled by oars. None of these really led to further warship designs, so they are only historical curiosities. The steam-propelled ironclads of the 1800s, on the other hand, led directly to the warships of today.