The Deterrent of Nuclear Weapons Doesn't Work in a War Between Equals

If the use china fight in all out conventional war, there will be massive destruction and loss of life on both sides. And that's an incredibly strong deterrent. Nuclear weapons might add to the deterrence, but it's not likely to be the thing that prevents war. The only place i can really see a deterrence effect of nuclear weapons is when a country has no credible conventional weapons to serve as a threat.