Battleship-calibre guns define the battlecruiser boundary

Contemporary battleship-calibre armament provides a practical boundary between battlecruisers and even very large cruisers. That test makes the Alaska class a separate classification problem because its 12-inch weapons were not the standard armament of new battleships in its own era. A design can also cross the boundary in the other direction by giving up the speed needed to choose its engagements. The Kongo class illustrates how battlecruisers rebuilt toward battleship protection did not necessarily become fully satisfactory battleships. A historical label therefore needs to be tested against weapons, speed, protection, and the standards of the ship's own generation.