The counterfactual turns treaty satisfaction into a diplomatic resource. Japan can present intervention as assistance to an old partner now fighting two powers, drawing on the memory of the Anglo-Japanese Alliance even though that agreement had lapsed. Britain would gain ships, aircraft, and pressure on Italy while losing any reason to restrict fuel reaching its new ally. American objections would carry less weight if Washington remained outside the war, which in turn gives the United States a strong incentive to join the coalition rather than let Britain and Japan shape the victory alone.
Notable Point · 3:20:54-3:22:55
Japan's treaty stake opens an Anglo-Japanese path
A Japan that sees the treaty order as beneficial could invoke the memory of its British alliance and enter the European war against Germany and Italy instead of joining the Axis.