This is the key question that everyone ignores. The islands are closest to Taiwan actually, and Taiwan has an extremely formidable defensive navy and airforce. If it werejust Taiwan vs. Japan, Taiwan would have a fairly decent chance to win all on its own.
There are 2 roughly equally sized camps on this issue in Taiwan from what I understand:
- The no-action camp
- The anti-Japanese, pro-"Chinese People" camp who believes that even if the CCP is the enemy from within, Japan is still the enemy from without, and thus the interests of the Chinese people as a whole are greater than the interests of either the CCP or KMT alone.
Were I in Xi's shoes, I would try and strike a secret deal with the KMT on this. Taiwan would be the decisive trump card in this faceoff against Japan.