[Skybird]

Define "nuclear war" please: scale and dimension of the exchange, nuclear-versus-nuclear or nuclear-versus-non-nuclear faction, was Nagasaki and Hirioshima a nuclear war in your meaning?

From a certain scaling on, the question of whether or not to retaliate against a nuclear full strike by full own strike, becomes pointless. That is when the longterm consequences of a nuclear war - that effect all the globe due to their range and dimension - will cast doom on everybody, no matter where, no matter whgom, no matter whether neutral or having taken sides. The question then turns from justification for nuclear war to justification for ruining the rest so far as well.