I'm not sure I buy it. This is not the cold war. China is economically entwined with the West now. A conflict with the US would be a huge step backwards for them.

The best outcome would be a negotiated denuclearization of North Korea. Which seems unlikely.

The next is some sort of limited military strike which sets their development back a few years and effectively kicks the can down the road for the next president.

The last resort is some sort of regime replacement - a return to active warfare. I agree with the professor. China should side with the US as it is in its best interest if this was the last resort.

The need for US presence, including the THAAD system would be diminished and a drawdown could be part of an arrangement between the US and China.