They already provide NK with most of their equipment and training, have partnered with them Syria and Iran on nuclear development and defended their territory with Chinese troops in 1950.
Nobody should EVER forget that North Korea is a wholly owned subsidiary of China and has been since the beginning.
In the same manner that we own SK.
That is just the reality of it. Large powers no longer fight wars because the distruction that it causes destroys all involved. The world learned this during the last world war and we are no longer interested in that occurrence with the new weapons that are ready to be brought to bear. It is one of the reasons that we no longer ‘conquer’ other nations. We don’t really want the land.
Instead, we fight ‘proxy’ wars through smaller nations. NK is simply the nation that we are fighting China with atm. In all reality though, war will be a reflection of the aggressor. If NK attacks, as I stated before, China is NOT going to get involved. It is simple as that.
The reason that China has been issuing statements of that like recently is that they are already relying themselves to abandon NK if they attack. It is HIGHLY unlikely that they will BUT China does not make a habit of relying on ‘likely.’ Again, China is not going to suffer the negative consequences of going to war over an errant dictator. IF SK was the aggressor then you would see china involved and we, in all likelihood, would not get involved at all.