I'm well aware China have their own nukes, and their policy around them. Would they invade Taiwan, and use a nuclear threat to cover it? Almost certainly not.

I'm well aware China have their own nukes, and their policy around them. Would they invade Taiwan, and use a nuclear threat to cover it? Almost certainly not. Yet. But Russia would, and have, in the case of Ukraine, and it has worked, in terms of preventing direct military intervention, whether it's 'credible' or not.