All Japan had to do was to provide the Nationalists with a few older weapons and ammunition that is not up to service by their front-line troops. For that, they waste fewer troops and weapons, plus do not have to fight an additional front. The Chinese would either declare neutrality and deny access to the Allies, or join the Japanese. Both the Chinese and the Japanese would be better if China was a neutral because then any attempts from Russia to attack China would be censored.

Within the limits of their participation, the Chinese could be providing Japan with available raw materials and creating a trade route.

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Lord, let me be the person my dog thinks I am.