I'll copy paste for you.
Don’t forget China’s claims on Russia
However, there is one more territorial claim, which China currently keeps on the back burner. It is against – who else? – Mother Russia herself. During the age of European colonial expansion, the Celestial Empire (China) was effectively dominated by the European powers. However, it was never carved up the way other countries and continents were.
With one exception: In the 19th century, China was forced to cede the Far East and parts of Siberia to Russia. During the 1960s and early 1970s, there were border tensions and even a number of armed clashes between China and the Soviet Union.
Small parts of Russian territory were then quietly ceded to China — and more recently, the two agreed to accept the current borders — but China believes much larger chunks of what is now Russia rightfully belong to Russia.
As if to settle these broader claims by osmosis, Chinese settlers have been steadily moving into Russia’s remote, economically depressed and underpopulated regions.
Stupid Russia, patient China
By asserting its historic sovereignty over Crimea, Russia has set a dangerous precedent for the Chinese as they look wistfully over their northern border. Those vast empty spaces of Russia’s Far East, full of all kinds of natural resources, are what China’s booming economy craves. And now its citizens live there too, much like ex-Soviet Russians residing in Crimea.
Russia not so long ago agreed to preserve and defend Ukraine’s existing borders. Breaking that agreement in a moment of opportunity creates a precedent for other countries with alternative border preferences, including China, to follow suit if the relevant opportunities arise.
True, Beijing will bide its time and will not do anything precipitous or unlawful. But when the time comes, it will not hesitate to re-assert its claims – and Russia will have no one to blame but Putin for providing a convenient excuse for a land grab, in the form of a powerful precedent in Crimea.