There are disputes overthere. Why do you exclude China from the issue while other countries have occupied the largest islands in the region?
A Chinese monarch 1,500 years ago, with his army a feudal thinking and the whole 9 yards rolled in and militarily conquered some lands and some ethnic people who lived there long before...and forced them to become his subjects.
Because of that event, all Chinese people everywhere now are the sworn superiors to that group of formerly conquered people. That land since then, now belongs to all the Chinese people.
It happened in the Qin, in the Han, and all the way to the Qing.
China still has not gotten over its feudal dictatorship mindset. This whole 'one China' thing is a historical LIE. Chinese history has been dominated by ethnic wars and hui (hui jiang de hui) all trying to conquer each other. They are expansionists and always have been. To them, it is a zero sum game. Either I am in charge or I am subjected to someone.
If anyone or any place had ever been conquered in the past, even 2000 years ago, feudalism still thinks that whoever those people are and whatever place that is, belongs to "zhong guo". China has always been an expansionist colonizing dictatorship.
The CCP better stay inside its 12 mile border. China is still racked with an inferior and uncivilized culture. China is not modern and still plagued with feudalism and colonialism of its own.
You want to know the truth? The British only played by the rules the Chinese set. The British only gave the Chinese rulers some of their own medicine. Under Chinese thinking and rationale, parts of China still belong to the British and they have the right to take those parts whenever they see fit.
China wants nothing more than to continue the cycle. China is not trying to take what is rightfully theirs. They are trying to claim someone else's stuff as their own.
When that is not enough they want the feudally conquered land of the Han, or the Tang, or whoever. Any justification will do.
Of course they have created this situation, the CCP that is.
At all different times in history two or three "China's" existed, all at the same time. The actual size of those dynasties got smaller or bigger on a regular basis. It was/is all about who controlled the land and who subjected the other party.
They also thought of themselves as literally superior to everyone else on earth.
Once you have been conquered by a Chinese emperor, you have been touched by diety, and hence you better recognize your place, and who it is that rules over you forever and ever.
THAT is Chinese culture. Pretty. Isn't it?