Mentioned in Allied literature of WW II dealing with Japan's naval builds, a ship called the Chichibu was thought to be a Japanese improvement on the German pocket-battleship idea, that is, a few battleship guns on a cruiser hull. The US Navy was so sold on the existence of this ficticious enemy ship that it actually built the Alaska-class 'large cruisers' to match it!

In "Grand Fleet" the Chichibu is designed to fight cruisers or heavily-damaged capital ships with large-calibre guns and torpedoes. Built in secret when Japan was considering withdrawing from adherence to the Washington and London Treaties, this stretched heavy cruiser could outrun all except a few of the world's fastest battleships. Two 16" turrets from the converted Tosa and a single triple 6" turret from the converted CL Mogami formed the main armament.

In the opening months of the war the Chichibu sank the British monitor Terror and a Dutch cruiser. At Savo Island she was Mikawa's flagship in the night engagement and destroyed two more cruisers, but when dawn broke the Cactus Air Force bombed and shattered her upperworks. In Yokosuka Naval Yard the Japanese rebuilt her as a fast CVL comparable to the USS Independence. She and Ikoma took aboard the last of the highly-trained naval aviators and together formed the 5th Carrier Division when Indonesia was threatened. Both ships' aircraft successfully attacked a dawn invasion fleet off Java but both ships were sunk later that afternoon by carrier HMS Gibraltar's planes.