South Korea and Japan are concerned about the Chinese military buildup, because the most likely Chinese strategy calls for attacks on U.S. aircraft stationed in Japan and South Korea.
Strategypage says that China would likely strike our bases in South Korea and Japan to keep our air power away from Taiwan. The Question is whether the Japanese and South Koreans would take the strike yet do nothing, hoping to stay out of the war.
I'm not so sure that Japan would stay out even if South Korea might. I'm more interested right now in the assumption that China will make a military analysis of the forces in the region and preemptively strike our air power in the western Pacific. If this was a standard military problem, I'd say sure, that's likely.
But this assumption relies on thinking of the issue as an international and miliary issue. China does not see it this way.
Taiwan is an internal Chinese matter as far as Peking is concerned. Why would China make the conquest of Taiwan an internaional issue by striking American bases in Japan and South Korea, making the conflicrt internaional from day one? Such an attack would simplify our thinking and instrad of perhaps a weeks-long debate in America over whether to intervene, we'd remember Pearl Harbor and gear up for a serioius shooting war with China immediately.
China wants to delay our entry while they blitz Taiwan. Loudly proclaiming it is an internal matter while throwing submarines and mine fields in our way and air planes over Taiwan to dare us to shoot first, China will buy time as we discuss whether to fight China over Taiwan.
I don't think China makes this an inter-state war right off the bat. I could be wrong, so I'd still harden our airfields and aircraft shelters while improving missile defenses in those locations, mind you. But that is a wise precaution regardless since once we are at war should it come to that, those bases would be attacked by China, I'm sure.
China wants a Taiwan Crisis to be a Taiwan only crisis. They may be willing to fight us over the status of Taiwan but Peking won't seek to start a war with us over the island.