Comment by smaug7

This to me is the correct answer. A lot of times in war it's not about logic or reason, it's about emotion and feeling. Throughout Chinese history, a leader is only "legitimate" or dare I say, have the Mandate from Heaven, when they have unified the country under one banner. It is a stain on their authority that there is "rouge" state outside the CCP's control. They will do anything to unify their country for national pride.