Just a few things...
1 Taiwan, then known as Formosa, was a Japanese possession until 1945.
2 How seriously did the Japanese take this? The code signal for the Pearl Harbor attack was “Climb Mt. Niitaka”, said mountain being the tallest in the Japanese Empire, and located on... Formosa. The initial air assault on the Philippines was launched from... Formosa. Kamikaze strikes on Allied ships around the Philippines and later Okinawa, launched from... Formosa.
3 Some Japanese naval and air force personnel either hung around or moved to Formosa and joined up with Chiang’s boys, on the principle that they hated Commies too.
China may try to take Taiwan, but it will get hurt in the process. And the Indians and Japanese (and the Russians! And the Vietnamese!) are sitting around waiting to drop the hammer on the wounded tiger.
This, of course, ignores the facts that the South China Sea is painted in big red, white, and blue letters ‘Property United States Navy’, and that the whole reason the US got into the Second World War was... the Japanese eating the Republic of China.
If China invades Taiwan, shortly thereafter there will no longer be a People’s Republic of China.