Battlecruisers were large
warships of the first half of the 20th century first introduced by the
British Royal Navy. They evolved from
armoured cruisers and in terms of ship classification they occupy a grey area between
cruisers and
battleships. Generally, battlecruisers were similar in layout and armament to battleships but they traded off
armour or firepower for higher speed, which showed in their more powerful engines and slender hulls; they still retained enough firepower and protection to be classified as
capital ships. On the other extreme, considerably smaller vessels which were upscaled
cruisers, such as large cruisers and
pocket battleships, are often considered by some to be battlecruisers as well.
See more at Wikipedia.org...