I wonder how much America’s defense against Iran’s ballistic missiles informed China’s calculus here.

Counter-missiles aren’t useful for stopping a first strike, because they’re more expensive per missile, and have a limited efficiency. However, in the event of a suprise first strike, say by stealth bombers, the counter-missiles only have to shoot down the ones that didn’t get hit in the first strike. That was the logic behind Reagan’s Starwars.

So the logic to defend against that is you either need a hair trigger that the enemy knows they can’t do a first strike without hundreds of missiles launching (this is fucking insane), you need launch sites the enemy knows exist, but not where (submarines, bombers), or you need a more launch sites than the enemy can hit.