The disposal of Britain's older 13.5-inch-gun capital ships answered an American concern about how imperial naval strength might survive nominal limits. If those ships remained, Britain could modernize them late in the 1920s, pass some to the dominions, and then add a new Royal Navy programme on top. Washington therefore had reason to insist that the older hulls disappear rather than merely leave the active British list. That concession also helps explain why the United States was willing to permit new British ships under the treaty. Arms-control calculations counted usable imperial capability, not merely the headline tonnage of the core fleet.
Notable Point · 39:49-41:01
Why Washington wanted Britain's older capital ships gone
American negotiators feared Britain could refit its 13.5-inch-gun ships, transfer them to the dominions, and still build a new fleet, so scrapping the older ships helped make fresh British construction acceptable.