When attacked, I nuke all the land approaches enemy forces are traversing and I will even take the hit and nuke hexes near a sieged city.
It's sort of funny to watch the AI stand in a polluted hex taking damage turn after turn.

Even if the AI nukes one of my cities the nuke takes out all surrounding features and improvements but the advancing AI has to take damage while trying to take the city.
It's pretty funny and I enjoy watching the AI troops die of radiation poisoning.
