"Battleship" is a term for a particular class of naval vessel, one which hasn't been built for 60+ years, and one which has not been in service anywhere for 20+ years. A battleship has 30+ cm of hardened steel armour - not 1.5 cm of mild steel hull plating. And guns of 28+ cm caliber. No guns of over 13 cm exist on any in service naval vessels that I am aware of.
The blunder is on the sub-title. The title and the text use the correct term, "warship".
</berserk mode>, sorry for the outburst.