MAD is not equivalent to nuclear parity, China does not have to match the US warhead for warhead to achieve MAD, They just need to credibly guarantee unacceptable damage to the US. Say if they can guarantee enough warheads to land on top 50 population centers it constitute unacceptable damage, IMO China has that capability already.
I never specified that MAD requires China to necessarily have the same number of nuclear warheads and delivery vehicles as the US.
I meant MAD/MV "with regards to" the US.
Now let me take a step back and say China does not have MAD. Since you're speculating the role of IC-HGV in the context of a possible future where US has ramped up their ABM interceptors to orders of magnitude of what they have now; Wouldn't it be fair for me to speculate the role of IC-HGV in a possible future where China has achieved MAD status? Considering the price tag on those ABM system I'd say it is much easier for China in ramp up ICBMs than for US to ramp up interceptors.
Not quite fair, because my suggestion for IC-HGV's role, is that it is being pursued to preempt and mitigate concerns over a US strategic response to an increase in China's ICBM arsenal (i.e.: seeking substantial strategic ranged BMD), to ensure that MAD/MV can be attained.
By contrast, the idea of using IC-HGV in a conventional role against CONTUS, operates on the assumption that MAD/MV has already been attained and is secure.
Putting it another way -- I believe that attaining MAD/MV may prove to be challenging in itself and the US will react strongly in a manner to try to maintain their superiority of enforcing greater vulnerability on China, therefore the IC-HGV is part of the way of the PLA's way of ensuring it is achieved. Whereas your position is assuming that MAD/MV has already been attained.
Policy wise; China can simply announce any attack on Chinese homeland will be met with proportional response in the form of IC-HGV be it conventional or nuclear. This policy is plain and simple, easy to understand and perfectly credible.
Place yourself in the position of US decision maker, say you decide to ignore the warning and attack Chinese homeland anyway, afterward you see a solitary ICBM launch towards you, would you just trigger a standard response knowing MAD is assured or would you rather wait and see?
The idea that the US would so easily give up its overwhelming geographical and military advantage in being able to conventionally strike the Chinese mainland while protecting its own CONTUS from conventional strikes is... understandable, but dubious.
In your situation, if I were the US, I would proclaim in turn that any detected intercontinental attack on the US homeland would be met with launch on warning use of tactical nuclear weapons against relevant military targets against the foe who conducted them, as it would be able to be trusted or ascertained if the munitions were conventional or nuclear, as a method of deterring China from launching conventional strikes against CONTUS to begin with, then by leaving the MAD ball in China's corner afterwards once the US has launched tactical nukes in response.
Now, I understand where you and others are coming from.
There is a desire to make it such that the Chinese mainland is as equally "untouchable" by the US, as CONTUS is "untouchable" by the PLA, in both the conventional and nuclear sense.
However, the relative vulnerability of each side's homelands is a function of geography and positioning of military forces, and it is not something that can merely be equalized by MAD and long range strike weapons.
The US has long held the capability to strike and bomb nations around the world with relative impunity, while retaining security and what is more or less "invulnerability" in its own hemisphere, with the one exception being that they remain vulnerable to nuclear delivery systems (i.e.: ICBMs).
I do not see the US giving up this massive privilege of relative homeland invulnerability without significant brinksmanship of its own, and it is that brinksmanship and the inability of us to predict or assess what said brinksmanship would look like (aka, evolution of US nuclear doctrine over the next 10-15 years) that makes me very cautious when talking about the idea of intercontinental ranged strikes against the US.
I am seeing this quaint idea whereby once China has MAD, they can simply procure some conventional IC-HGVs, and then try to deter US conventional strikes against the Chinese homeland by holding a few targets in CONTUS to conventional risk, but this ignores the massive advantages that the US holds in geographical positioning of military forces in the region and the significantly greater ability to deliver quantities of munitions (whether it be conventional or nuclear) to Chinese population/economic/political/industrial centers, than what China is able to deliver to the US, that cannot be remedied short of use of strategic counter value nuclear weapons.
