If you read more history of China, you will also notice that the Han ethnicity prefers letting others adopt Hans customs and cultures instead of actively adopting or adapting to foreign cultures. That's another striking characteristics in my opinion.
Also, 80,000 Chinese soldiers invaded Vietnam in 1978, with the intention to take Hanoi. It was by no means a minor skirmish.
The US had repeatedly sworn to not cross the 38th parallel in the past. Once the US decided to invade North Korea proper, Truman's promises to stop at the Yalu River no longer seemed credible to China's government. Note that Beijing is very close to Manchuria, and both the Manchus and Japanese invaded China along this route in the past.
The US has certainly threatened war against any foreign powers that interfered anywhere in the entire Western hemisphere [3] -- not sure how anyone can then turn around and fault China for reacting to American troops driving right up to its Manchurian border. Remember this was in 1951, the Cold War was getting warmed up, and the US had nuked Japan only a few years earlier. No responsible Chinese government could have ignored the very real and credible threat of another invasion.
The Vietnamese invasion has an interesting history -- the PLA invaded, failed to achieve its main objectives, then marched right back less than a month later. Certainly not a full-scale invasion nor an occupation, considering the proximate cause was to 'punish' Vietnam for invading Cambodia.
[1] http://www3.nccu.edu.tw/~lorenzo/Hao%20Chinas%20Decision.pdf
[2] https://en.wikipedia.org/wiki/Korean_War#China_intervenes_.2...
""" Qing dynasty rule in Tibet began with their 1720 expedition to the country when they expelled the invading Dzungars. """
""" For several decades, peace reigned in Tibet, but in 1792 the Qing Qianlong Emperor sent a large Chinese army into Tibet to push the invading Nepalese out. """
""" As the Qing dynasty weakened, its authority over Tibet also gradually declined, and by the mid-19th century its influence was minuscule. Qing authority over Tibet had become more symbolic than real by the late 19th century,[35][36][37][38] although in the 1860s the Tibetans still chose for reasons of their own to emphasize the empire's symbolic authority and make it seem substantial.[39] """
[1] https://en.wikipedia.org/wiki/Tibet#From_1950_to_present [2] https://en.wikipedia.org/wiki/Tibet_(1912%E2%80%9351)
The South China sea stuff is indeed China throwing its weight around, sure, but need I remind you that China's foreign interventions has been far more restrained than, say, the US (Iraq 1 and Iraq 2, Afghanistan, Libya, Panama) or Russia's (Afghanistan, Ukraine, Syria) even in the last three decades.
Going back slightly further, Japan invaded and occupied half of China and killed millions of Chinese people over the course of a decade, while it was the US that invaded, nuked, and then occupied Japan, even though the US never suffered civilian casualties from Japanese attack. Yet you don't see the Chinese government crying out for bloody revenge, do you?
One the one hand, we have China asserting claims to sea resources and sea lanes there are right in its back yard, where it has a legitimate strategic and national interest. On the other, we have the outright invasion, occupation, and overthrow of sovereign governments. Which country is objectively more peaceful?