[url]https://en.wikipedia.org/wiki/Flexible_response[/url]
Of course we roughly already use this but details like the "no-cities" policy can be added as a worldwide guideline.
And as I said, using nukes to destroy cities is a war crime even if it's a desperate all-out war.
We can add further details if needed like if a nation only employs sub-kiloton tactical warheads on military targets that wouldn't warrant the use of ICBMs and MIRVs, for example.
Though in general we have yet to use our military assets at all in this RP.
Of course cautions are never too early to make.
:lol