The french invaded russia and lost, as did the germans. The mongols invaded russia and conquered. China is getting more and more aggressive and will need more resources and space to expand.
The russians can do as they please, defensewise, meanwhile the east is going to kill them.
While I have mixed feelings about NATO expansion, that organisation has not attacked russia.
China won’t need to invade Russia. They can just walk in and take it when demography leads to the depopulation of Russia’s far East. Russia is a dying nation....