The Washington treaty set a 10,000-ton ceiling for each cruiser, while the London treaty later imposed cumulative cruiser limits. Under Washington rules, the United States remained free to build another cruiser so long as that ship stayed within the individual ceiling. The weight devoted to Lexington's twin eight-inch turrets could therefore support a more capable carrier without consuming a scarce aggregate cruiser allowance. Under London-style total limits, the argument for retaining the carrier's heavy guns would be stronger because every separate cruiser would use part of the fixed total. The accounting rules changed the value of the same design feature.
Notable Point · 24:34-27:14
Why Washington treaty rules weaken the case for Lexington's eight-inch guns
The Washington treaty capped individual cruiser size but not aggregate cruiser tonnage, making a separate cruiser preferable to heavy turrets on a carrier.