China has spent the last few years cosying up to South Korea. It would not start WW3 to save Kim Jong Il. North Korea is a useful barrier, but also embarrassing, expensive & dangerously unpredictable. South Korea, on the other hand, is a well-behaved & highly valued trade partner.
In the highly unlikely event of a new Korean war, I can only imagine China intervening after a N. Korean collapse, to occupy border areas of N. Korea in order to
1) keep the flood of N. Korean refugees out of China
2) keep the US armed forces away from the Chinese border
3) have something to bargain with in the post-war settlement, which might, with a bit of luck, be exchanged for US withdrawal & a great reduction of the military strength of a united Korea.
I expect that any such Chinese intervention would be accompanied by lots of noise about its peaceful intentions, details of exactly how far the PLA would advance, requests for liaison with the S. Korean forces to prevent accidental conflicts, etc.
In the highly unlikely event of a new Korean war, I can only imagine China intervening after a N. Korean collapse, to occupy border areas of N. Korea in order to
1) keep the flood of N. Korean refugees out of China
2) keep the US armed forces away from the Chinese border
3) have something to bargain with in the post-war settlement, which might, with a bit of luck, be exchanged for US withdrawal & a great reduction of the military strength of a united Korea.
I expect that any such Chinese intervention would be accompanied by lots of noise about its peaceful intentions, details of exactly how far the PLA would advance, requests for liaison with the S. Korean forces to prevent accidental conflicts, etc.