Story-wise, the American nuclear arsenal deployed in Europe can be reduced by Soviet nuclear attacks on the airbases the nuclear weapons are stored in.
That was a perennial American worry. The problem with that is that the Soviet doctrine around nuclear weapons employment during the High Stalin-era was... well, they didn't have
one. Stalin basically viewed nukes more as prestige weapons than anything else and straitjacketed the Soviet military thinking on the subject of nuclear ordinance. The explicit idea of using ones own nuclear weapons to pre-empt and destroy the enemies delivery capabilities don't emerge until after Khrushchev takes over. Looking to conventional Soviet bombing doctrine doesn't lend much confidence : when it wasn't being tied to it's usual army (or navy) support role, the VVS tended to revert to old-fashioned psychological terror bombing in the Dehoutian model, which we know now to being pretty useless. That suggests the Soviet bombs would be employed to simply try and terrorize the enemies populace, when they are not deployed for operational purposes (like, for example, dropping one on the harbor of Pusan to cut the supplies to the Americans in Korea).
Now, one could argue that maybe the sudden nuking of targets in China (minus those which get intercepted) might focus Stalin's attention on the subject, but that's speculative.
How far could the Soviets really supply an advancing 5.7 million man army as nuclear strikes start happening all over Europe?
Why do you think that in the rest of that post I'm emphasizing the fact that Western forces have thoroughly integrated themselves with nukes as being the decisive factor here?