Hiyo class and Japan's conversion gamble

The Hiyo approach was a rational response to Japan's limited slipways and dry docks: build commercial liners with conversion potential, then add flight-deck structures when war demanded more carriers. Because much of the conversion involved removing the merchant superstructure and adding a hangar, island, and flight deck, smaller finishing yards with a quiet berth and suitable crane could perform work that did not require a large building slip. Their slower speed was less important than starting the programme too late and producing too few convertible hulls. Japan also needed reserves of aircraft, maintainers, aircrew, and leaders. An aviation system that selected roughly the top 1 percent could not create the mass that wartime operations required, whereas the discussion suggests drawing from perhaps the top 20 percent and allowing trainees to recover from mistakes. The ships could supplement losses before a decisive battle, but hulls without mass training and air-group organisation could not restore strike power.