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Japan has made it clear that if Beijing launches a war in the Taiwan Strait, it will send its Self-Defense Forces to help defend Taiwan! Then Beijing will use "tactical nuclear weapons" to make a quick battle during the "armed reunification"!
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If PLA attack Japan, US forces will enter the war due US and Japan alliance
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That's the plan between US and Japan. Once Japan sent forces, and get involved militarily with China , US can enter officially due to US and Japan alliance.That was until recently against the Japanese constitution. Japan abdicated of the right to pursue war. The Self-Defense Forces could only operate in case of an attack against Japan, not Taiwan. I think they recently added an exception for peacekeeping forces but that would likely require a UN Security Council mandate which would likely be vetoed by both China and Russia. Plus if Japan did send in their fighter aircraft and navy the Chinese could simply use MRBMs like the DF-26 to strike at Japanese naval task forces and airfields.
China does not need to use tactical nukes against Taiwan proper because of the massive superiority they have in conventional weapons versus Taiwan. Taiwan is in range of mainland China. The PLA could simply saturate the relevant areas of Taiwan with their MRLS. If Japan and the US actively enter such a conflict, the US risks to lose all their bases and troops across the 1st and 2nd island chain.
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MRLs not enough to break open the mountain military hideout
Not even that. The US will use the Japanese bases so China would have to respond by attacking these bases. , then Japan will have the "self-defence" excuse and go to war.That's the plan between US and Japan. Once Japan sent forces, and get involved militarily with China , US can enter officially due to US and Japan alliance.
Japan will breach whatever UN restriction if unification war does breakout.
MRLs not enough to break open the mountain military hideout