The old bear may be wounded, but it is far from dead. China would do well to let it sleep, else the Red Dragon may find its head in a scarred, mighty paw.
I have little doubt the Chinese would make good progress initially, until the sheer vastness of Russia hits home. Then there is the, as I understand it, recently professionalised Russian Army that will shed its blood for every inch of the "Sacred Motherland." Russians do not make peace with invaders until they are ejected or outright destroyed, and they do not lose wars on their soil. History has proven the Russian fighting man can suffer unbearable hardships in the defence of his country, hardships which I doubt a culturally damaged automaton of a Chinese conscript will put up with. Then there is all the old Cold War equipment they are upgrading for functional use, giving Russia access to a veritable armada of armour. This is one of the most heavily mechanised armies in the world, after all.
Above all, Chinese troops in Russia would force the country to unite around Putin, demanding he continue to prosecute the war until the perfidious invader is ejected to which he will happily comply and massively expand the Russian military. Meanwhile, the Chinese Communist Party continues to lose face as their army is bled dry whilst the voices of dissent grow louder. It would be rerun of the Great Patriotic War without the ideological zealotry.
The Russian Bear can only ever be contained. It cannot be overthrown in its own lair.
Do not confuse Russian West for Russian East. It would be a very different war than what happened in Europe. Ultimately, Russia naturally had the advantage of being a bigger, more populous country against all its historical invaders, and once it got its shit in order, could crush them in superior numbers of soldiers and tanks, while these wars happened relatively close to its population and logistical centers.
en.wikipedia.org
But the war in Far East would be quite different. Its a ridiculous amount of land, about one and half USA, populated by probably less than 6 million people as of now, with barely few strategic logistical routes crossing it. Airpower, maneuver warfare and combat engineering would rule. No need to get bogged down in Stalingrad like urban warfare, or worry about populated countryside creating a guerilla threat, just go around cities, China doesn't need their people, it has its own, it needs the resources around them.
Meanwhile, the 3 provinces of China neighboring the Far East have a population in low 3 digit millions, and proportionally good logistical access to the region.
Of course China also has no shortage of heavy equipment and keeps churning out more, while Russia is waning in that department - compare the numbers of their newest gear they are rolling out to the modernized ex-soviet stuff that is bound to become too outdated or old eventually. Time is playing in China's favor in this regard massively, which is one of main reasons why they aren't making moves yet.
Simply put, China is a country whose military is still being built up to its economic capabilities, while Russia, the opposite - due to still benefiting from fruits of Soviet Union's ridiculous military spending it is better off than it can afford on its own economy in long term.
This war is a closer comparison, as it does involve Russia defending Far East.
en.wikipedia.org
