American support could frame the conflict as part of the effort to resist Japan's war in China, giving intervention a political as well as naval purpose. The Soviet Union was already fighting Japan in 1939 and might also enter the wider struggle. Japan would have to consider the Philippines quickly because it lacked the Indochinese bases later used to support the Malaya campaign. Attacking Hong Kong would also be harder while Chinese Nationalist forces remained less depleted than they became by 1941. The naval counterfactual therefore cannot be separated from Japan's existing continental overextension.
Notable Point · 2:25:27-2:28:40
China and the Soviet Union widen Japan's strategic crisis
A 1939 maritime war would begin while Japan was still heavily committed in China and potentially fighting the Soviet Union.