The bombs are already here.
They will wait for us to move against them before the detonate them.
It doesn't matter to their leadership if we nuke them back. They will have done something to us that's never been done.
There's a first (and only) time for everything, like flying loaded airliners into skyscrapers.
Personally, with nukes, I would eliminate even that first attempt.
If it must come, let it be clear:
The results to your country, and to your people, will be awesome and horrible beyond belief.
Let us then see, once we have delivered on our promise, who will be the second to attempt it.
Even the dumbest animal is never suicidal.