Japan could plan treaty cruisers for later wartime up-gunning. A triple 9.2-inch turret and barbette sized for replacement by a twin 12-inch mounting is treated as plausible. Such a design would let the ships serve as treaty-compliant high-end cruisers in peace and move closer to the battle line after reconstruction. Japan might still retain the 9.2-inch battery because its rate of fire remains better suited to the cruiser's wider duties.
Notable Point · 2:14:17-2:14:49
Japanese convertible cruiser turrets
Japan might design a triple 9.2-inch mounting whose barbette can later accept a twin 12-inch turret.