Germany's treaty restrictions made Japan and Italy more immediate naval planning concerns during the 1920s and early 1930s. In the Japanese case, relatively little of the trade under consideration ran into the South or East China Seas. A fleet concentrated at Singapore was expected to restrict Japanese access to the main routes, with forces at the Falklands and in the Caribbean covering possible approaches to the Atlantic. Japanese submarines could still threaten the Indian Ocean, but existing bases around India and the Red Sea made additional mobile aviation support harder to justify.
Chapter · 9:29-12:42
Why prewar threat planning sidelined seaplane tenders
Expected wars with Japan and Italy shaped interwar procurement, while Singapore and existing Indian Ocean bases appeared to limit the need for mobile aviation support.