First armored battleships are believed to have appeared in the 19th century.
But few know that first armored battleships appeared, were built and actively used in Korea as early as the 16th century.
Geobukseon, or “a turtle ship”, was a wooden vessel with a roofed hull. The roof was made of overlapping spiky iron sheets. The ship could go under sail. At the sight of the enemy sails were lowered and the ship was driven by oarsmen concealed on a shielded gallery.

The ship design was extremely good.
The spheroidality of the convex roof, included in the load-bearing structural skeleton of the hull, ensured additional stiffness. That is why Geobukseon was undestroyable in a ram attack of the enemy.
The iron sheets of the roof were a reliable protection against incendiary arrows – the curse of the wooden ships at that time. The crew hidden by a reliable roof could actively shoot through special shot holes. Those who wanted to board the ship were awaited by the roof spikes, and to get inside the ship, they had to hustle through fiercely defended narrow manholes.