The Number 13 proposal was a potential culmination of Yuzuru Hiraga's capital-ship work. His later ideas included an octagonal armour citadel as one way to fit demanding protection requirements within a 35,000-ton limit. A balanced ship with 16-inch guns, substantial protection and a decent anti-aircraft battery was exceptionally difficult to accommodate at that displacement. The later American South Dakota design provides an example of an extremely compressed solution, while Hiraga pursued different arrangements. These proposals remain open to criticism as engineering choices, but their unusual geometry directly addresses the weight and space problem imposed on the designer.
Notable Point · 1:59:08-2:01:22
How Hiraga searched for balanced treaty battleships
Hiraga's octagonal citadel illustrates the unconventional layouts explored to fit 16-inch guns and adequate protection within treaty displacement limits.