The 1930 London Treaty redefined an aircraft carrier as a warship designed exclusively to carry aircraft that could take off from and land on it, regardless of displacement. Ordinary aircraft platforms on battleships, cruisers, and destroyers did not automatically make those ships carriers. The treaty also barred landing-on platforms or decks on capital ships already in existence on 1 April 1930. These rules closed the sub-10,000-ton route used for Ryūjō without solving navies' need for small carriers. A proposed alternative would give carriers of 15,000 tons and below a separate category and cumulative allowance, allowing small-carrier development within an agreed limit.
Notable Point · 36:45-38:40
The London Treaty closes the Ryūjō loophole
A revised carrier definition brings small Japanese designs such as Ryūjō inside treaty accounting, prompting a counterproposal for a distinct light-carrier category.