Hong Kong was leased by the British from China for 150 years directly as a result of the Opium wars. Bit shit that we didn't introduce a democratic system for administration until it was nearly time to hand back.
The Chinese nationalists KMT were ousted by Zedong's Communists after the civil war of 1949 and fled to Taiwan. The island of Taiwan and been inhabited cy the Chinese for at least hundreds of years, probably longer, it's only 100 miles off the mainland. I think right up until the 70s the international community recognised the Nationalists government as be the "true" government of China, hence why for decades they didn't compete at the Olympics.
Like I say that changed in the 70s and Peking was acknowledged. Particularly since the 80s Taiwan has become much more democratic and the influence of the KMT who favour reunification has waned. In the last decade Taiwan has become much more independently minded. At the same time they've invested over £1.5 billion in the mainland.
Pelosi who's due to retire soon has provoked this crisis. Both the Chinese and Taiwanese were happy to have a rather nebulous, deliberately ambiguous relationship, with the understanding that the "rebel province" would eventually rejoin. Find it very strange that people seem to be talking a new "domino" theory with Taiwan being the lynchpin. China is flexing it's considerable muscles, as it sees the west as both weak and provocative. Hopefully by Sunday once their exercise has finished, both parties can settle down again.