I'm not talking about a strict legal interpretation.
I'm talking about how the global view is that the Senkaku/Diaoyu Islands are in dispute.
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And here we come to the crux of the problem. The Senkaku/Diaoyu are a bunch of uninhabited islands taken during the First Sino-Japanese war.
Plus need I remind you of what has happened in Ukraine? Ukraine did not accept or tolerate the Russians moving in.
But that still doesn't change the fact that they have lost badly, partly because the US and Europe have no wish to go to war with Russia which would inevitably go nuclear.
The Russians haven't exactly come out as winners either, but they should be able to get past it. We can already see the US and Russia working together in Syria with joint airstrikes
So yes, without US involvement, China could push its air force to the Senkaku/Diaoyu Islands. But having the US around does inject uncertainty. Plus China would have to consider very carefully the risks of trying to establish air superiority over the Senkaku Islands.
My view is that they probably wouldn't do this as it would be too risky and it would threaten to derail China's domestic development. But if relations do continue as they are with Abe, I can definitely see the Chinese Coast Guard or Navy moving towards those islands, as there are all sorts of games they can play against the much smaller Japanese fleet.
Look at how we saw a joint Russian/Chinese naval contingent sailing near the islands recently and causing panic in Tokyo. Or if China sends in the monster coast guard ships (is it innocent passage or an assertion of sovereignty?), and the only way they can be stopped is if they are sunk by the Japanese Navy. But then will the Japanese Navy have started a battle which they cannot win against the Chinese military?
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At the end of the day, Japan needs workable relations with China, otherwise it will be always be insecure and vulnerable. Everyone else in Asia already realises this.