What exactly is a battlecruiser?

Answer 1

SUMMARY: Battlecruisers and Heavy Battlecruisers are lightly armoured by contrast to similar sized ships, but much faster, and typically with better weaponry.

Initially, at the beginning of the 20th Century, a Battlecruiser was a type of heavy warship. Warships are designed with 3 main things in mind: Speed, Durability and Firepower.

In the case of a Battlecruiser, armour and durability is exchanged for providing a much improved top-speed and heavier firepower. The reasoning behind this is that a ship with larger guns can hit much further, and a faster ship can always stay out-of-range of the opposition. Thus, a Battlecruiser could chase-down even the swiftest opponent, and still be able to match the firepower of the largest battleships.

Good examples are the HMS Hood, the most powerful ship afloat at the time, and the German Graf Spee, an exceptionally successful vessels, lethally effective against slightly smaller destroyers and frigates.

Heavy battlecruisers were much larger, typically the size of battleships, but with much more powerful engines, making them even faster than battlecruisers, but with heavier armour. A famous Heavy Battlecruiser was the German Bismarck which, due to it's size and mass, was mis-labelled as a battleship. The Bismarck was not as well-armoured as British ships of similar size, but was almost 70% faster.