By 1935, despite having been given extensive refits, it was obvious to all that the
Amagi-class battlecruisers, let alone the preceding
Kongo-class, weren't going to be around forever. So it was decided to develop a new battlecruiser design. The hull selection was no problem, for the hull that had worked so well for the three classes of large cruiser was fairly easy to produce now that the shipyards that normally built major combatants had already built fourteen of them. The guns took some time to design, however, with the Naval General Staff wanting a ship that had bigger guns than the large cruisers, but not as large as the
Amagis. Therefore a new 12.2-inch gun was designed, and the ships were designed to mount three triple turrets. The new four-ship
Tsushima-class had commenced construction by mid-September 1941, with the four vessels all entering service between early September 1943 and late July 1944.
In early 1941, the Naval General Staff ordered four more
Tsushima-class ships, but the Naval Construction Corps managed to get the additional vessels upgunned to three triple 14-inch turrets, and therefore they became an entirely different class of vessel: the
Iwaki-class. Laid down between late February 1942 and mid-March 1943, the four ships were commissioned between early January 1945 and early February 1946.
(A special thanks to ALVAMA for allowing me to use these drawings in my AU. Heuhen was credited for drawing the 14-inch barrel I used, and BB1987 was credited for updating it.)