You see the Chinese flag has five stars.
"五族共和" (Five ethnic groups together in harmony) -- Thank you Gudong.
This should be of particular importance to Koreans as this was the main reason given by the Chinese government as to why the Chinese government claims Goguryeo as a kingdom in Northeast China as a minority Chinese kingdom. The logic being that since China is not a nation of a single ethnic group -- as in an Israel or Korea -- then it is possible for those people of Goguryeo or even Koreans to be ethnically Korean, but their nationality to be Chinese.
Of course, with uprisings in Tibet last year (and comparisons with Native Americans by Han Chinese) and Xinjiang this year, we all now know that just like communism, this concept or ideology of Chinese nationality is, well, bankrupt. China is a nation of Han Chinese who are systematically taking advantage of her ethnic minorities and continuing a ten-thousand year history of absorbing smaller, neighboring countries and ethnic groups one-by-one. Interestingly, the first character, "Xin" (新,신), Xinjiang, represents new as if it's some new land for the Chinese to settle.
This process of conquest and assimilation is not just a communist thing, you see. The Republic of China (Taiwan), even claims what is left of Mongolia. And, this I believe is more of a Chinese thing. This has been going on for hundreds and hundreds, no thousands, of years (Think about the initial assimilation of the Cantonese civilization). But, the easiest way to look at it is by looking at something none other than where the Great Wall of China is.
You see, for most of history, well, up until 1644 (when the barbarians conquered China for good), the Great Wall was meant to protect civilization (China) from the uncivilized or not as civilized (the rest of the world, pretty much). China was pretty much "contained" to the east coast with tributary states to the northeast (Korea, Japan) and to the south (Dai Viet, though, this state was directly ruled by the Chinese as late as during the Ming period), but did at times directly rule over states in the west. Nonetheless, even as late as the 19th century, when Manchurian rulers finally allowed the Han to settle in Manchuria (those areas northeast of the Great Wall), most of Manchuria was scarcely populated and the region was devoid of Han Chinese, which certainly is not the case today. Much of the lands that were occupied by barbarians are now part of China proper and the barbarians there speak Mandarin.
I remember a few years ago the term that China kept using was the "peaceful rise of China" or so, as if, to tell the world that you know what, the middle kingdom -- literally (中國), is returning to it's proper place as the center of the world and will do so in a very peaceful way. By the way, I'm sorry to tell you Sinophiles out there, but I doubt this will ever happen again, for you see, the United States is now here and by geography and ideology (and, perhaps, even destiny) the country sits right in the middle -- between the West and the Far East.
The last time the Han Chinese tried to conquer Korea (7th century C.E.) when the Tang turned on Silla, the Tang were much bigger than Silla, but nowhere near the proportions that either one of the Koreas today faces (This is one of the reasons why I believe North Korea has a nuclear weapons program and why I believe a unified Korea will need either a nuclear weapons program or an iron tight alliance with the United States for perpetuity). Do you think Korea could have survived up until today had the Chinese borders been like how it is today for the past couple thousand years?
I'm not disputing the territorial claims that Communist China makes with respect to Tibet nor Xinjiang (though Taiwan is a whole another matter, but that's for another day), but I'm pretty sure nobody believes the Chinese government's definition of what it means to be Chinese now.