New ships were sent east both to demonstrate presence and to test their performance in tropical waters. Japan could concentrate its second-tier navy in one theater, while Britain had to retain forces against Italy and, increasingly, Germany as well. The Mediterranean was also an arterial reinforcement route to the Far East, so Italian power affected any supposedly separate Pacific calculation. This asymmetry explains why treaty ratios that looked balanced on paper could leave British naval officers facing an uncomfortable global allocation problem.
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Why Japan shaped Royal Navy cruiser requirements
Royal Navy studies considered the United States as the strongest test case, but Japan was the practical Far East threat around which new cruisers had to be evaluated.