Throughout the following, Russia, China, and NATO are interchangable, or you could add other participants (Nazi Europe) for three-sided cold war gone hot strategies.
Russia nukes China. NATO knows that THEY didn't nuke China, so the perpetrator MUST have been Russia. In this case, NATO has a number of options.
1) Tell China they were attacked by Russia.
Pros: China could launch an immediate strike against Russia, leaving NATO alone. Two enemies are destroyed, NATO survives.
Cons: Russia could intercept the message, and become formal enemies with NATO, sending nuclear missiles towards them, or invading with conventional armies as a pre-emptive strike. If China is going to send nukes towards Russia, well, Russia doesn't want NATO to survive the conflict unscathed.
Pros: NATO knows Russia doesn't want to get a Chinese salvo and a NATO salvo of nukes. They might not attack, and just ride out the nuclear exchange from China.
Cons: Russia will have time to prepare for a nuclear attack from China.
2) Don't tell China that Russia was the perpetrator.
Pros: Russia might not attack NATO.
Cons: China will wait a while to try and confirm who attacked them, lest they prompt a second nuclear attack from a neutral power. In the meanwhile, Russia could invade with conventional forces, maybe even remove China's ability to send nukes.
Pros: Might force Russia to make more nuclear attacks to 'clean up' hostile areas, depleting Russia's nuclear resource.
3) Nuke Russia for attacking China.
Pros: Pre-emptive, Russia doesn't have as many nukes, and their launchers are aimed towards China.
Cons: Russia still might have gotten enough time to get into nuclear shelters, if they have any in this ATL.
Pros: China probably won't nuke NATO.
Cons: China retains their full nuclear arsenal, while NATO has nothing. During the exchange, China might very well nuke NATO, to bring all superpowers down.
4) Nuke China.
Pros: Russia will not attack NATO. Relations with Russia will hold.
Cons: China might launch missiles towards everyone, but two full nuclear strikes could destroy their launching ability.
Cons: The Cold War will probably continue, between only two powers.
Pros: The possibility of disarmament between the two surviving powers exists.
Cons: Revolution throughout NATO for joining their enemy to devestate an already devestated nation.
In most situations, in response to Superpower A nuking Superpower B, Superpower C stands to gain the most by staying out of the conflict. However, this means Superpower A would be smart to get rid of both Superpower B and C at the same time. However, if it does this, it splits its arsenal and is attacked by twice the amount of nukes.
The best strategy is for Superpower A to send a small amount of nuclear missiles towards Superpower B, convince Superpower B that Superpower C attacked them, and then send the rest of their arsenal equally between B and C. Superpower C will probably attack Superpower B once this deception is observed, which is why its imperative for Superpower A to send their nukes at the same time Superpower B does towards Superpower C, while AT THE SAME TIME, finishing the job by nuking Superpower C.
Complicated game, thermonuclear warfare. That's why I like to play DEFCON.
