Ryūjō tested the sub-10,000-ton carrier loophole

Ryūjō began as an attempt to place the largest possible air group on a hull nominally below the 10,000-ton counting threshold. That cutoff counted Hermes toward British carrier tonnage while leaving Argus outside it, so the threshold shaped the existing fleet as well as new Japanese designs. Ryūjō was about 8,000 tons as built but reached roughly 10,600 tons after the changes needed to make the design workable. Twelve boilers, 65,000 shaft horsepower, weapons, and flight facilities consumed a larger share of the small hull than the same fixed systems would on a fleet carrier. Her top-heaviness and poor efficiency show why treaty incentives could produce a legal design that delivered less aircraft capacity per ton than a larger ship.