[intransigent]

Well, the idea of global doomsday for all, beyond mere tactical retaliation, is probably drawn from the media, with movies like Dr. Stangelove playing the part of the primary narrative.

As to how much any world power has actually strategized and mobilized resources toward such an end (deliberate global suicide that destroys both sides by design) is likely to never be fully revealed, since it's a slightly alarming idea.

Even so, some of the plans that have been revealed really are quite terrible. Bad enough, that the difference between deliberate and accidental nuclear winters could be considered an argument that splits hairs.