If

the main thing is that it's not in the ground :)

but overall, the question is too vague to answer with specifics. My actions will depend on who is fighting whom and why. If there is a side I sympathize with, I will most likely participate. If not, then if possible I'll remove myself from the situation; if not possible, I will either remain neutral and be friends with everyone, or fight against everyone.

Added after 7 minutes

without the use of nuclear weapons (in case some system is developed capable of intercepting warheads with 100% probability, or the sides simply decide not to use them fearing a nuclear winter)

1. nuclear winter is a myth
2. I've gotten the impression that those at the helm of nuclear powers are often such psychos that they cannot calculate the consequences of their actions. So I'm not betting on the fact that nuclear weapons won't be used :(