Britain might protest but avoid war over Vichy Indochina, encouraging Japan to seek embargoed oil in the Dutch East Indies. That second move is harder to ignore because the islands remain aligned with the Free Dutch and are covered by British and Dutch naval forces. An invasion launched from Indochina is operationally possible, but it demands unusual cooperation between the Japanese Army and Navy. Churchill can intervene with a powerful Indian Ocean fleet, while Roosevelt can frame war as a response to aggression intended to evade American sanctions rather than as a favor to Britain.
Chapter · 53:18-59:16
Japan's southern move triggers an Allied war
Japan may still occupy Vichy Indochina, but an attack on the oil-rich Dutch East Indies brings Britain and the United States into the war against it.