I just happened across an interesting article that says Moscow's ballistic missile defenses will only protect against a maximum of two US ballistic missiles:
And that is how they would perform
before a counterforce strike degrades them.
It's kind of like the situation with the US missile defense system. It is only able to intercept a small attack, and is completely useless against a large attack.
Back in 1985, yes, it was thought, that with relatively poor Soviet computers and relatively new American warheads, their new A-135 ABD system needs 5 counter-missiles to hit one real incoming warhead and, less than 100 missiles (allowed by ABD-treaty) can hit say, twenty warheads, delivered by two LGM-118 Peacekeepers (up to twelve Mk21 reentry vehicles each).
But, the things had changed dramatically since 1985. Right now, Moscow is defended by fully operational (since 2021) A-235 system, which has unknown (because ABD-treaty was cancelled) number (but definitely more than one hundred) of counter-missiles of three echelons - long range A-925 missiles, medium range - 58R6 missiles, short-range - 45T6 missiles, much better radars, computers, optical systems to distinguish real and fake targets and be able to work even with nuclear bursts in atmosphere and outside it.
Also, their air-defense, from S-300V4 and higher, can intercept ballistic targets moving with velocity lesser than 4,8 km/sec - incoming RVs in atmosphere.
What is even more important, American nuclear forces were effectively degraded by the American nucleophobic (and/or corrupted) politicians. Right now the USA don't have Peacekeepers at all, and Minutemen have only one Mk-12A/Mk-21 reentry vehicle per missile without any modern counter-ABD measures.
And that means, that the Russians (if they won initiative) can more or less successfully defend Moscow region against at least 100 Minutemen and, if they are lucky - against all 400 of them or against full salvo of one or even two Ohios (20 missiles each).
And this means, that their even moderately successful first counter-force strike can make impossible American "Moscow-flattering" retaliation strike.
What is even more important, American all-out retaliation strike could make the USA defenseless against Chinese nuclear strike or Latino-American military invasion.
That means, that right now the USA don't have Deterrence Type III (ability to fight a limited regional nuclear war) at all, don't have Deterrence Type II (ability to answer by a nuclear strike against extremely provocative behavior other than a direct nuclear attack against the USA), and relatively weak Deterrence Type I (ability to answer on direct nuclear attack against the USA itself) - under some circumstances the Russians can decide that the direct counter-force attack against the US nuclear forces is more safe for them, than alternatives.
