A larger Japanese fleet could have supported a greater commitment to the European war, including an offer of dreadnoughts for the Grand Fleet or Kongo-class ships for the battlecruiser force. Britain would have found such an offer difficult to refuse while depending on Japan to help contain German surface raiders in the Far East. Japan nevertheless had reasons to retain major units near home, particularly concerns about Russia and the United States. Russia had only recently fought Japan and was struggling in Europe, so Tokyo could not assume that it would remain fully committed there. Relations with the United States also carried the legacy of America's forced opening of Japan. These constraints frame the counterfactual, whose wider outcome remains open.
Notable Point · 29:18-31:39
Why Japan did not send more of its fleet to Europe
Japan could have offered capital ships for European service, but concerns about Russia and the United States limited how much force it could spare.