Actually, the areas where the millitary are based at will probably be the safest since there’s like a zero percent chance that they will be siding in significant numbers with the likely instigators of this hypothetical civil war.
It’ll less be “the trenches have come across the atlantic” and more “The troubles but instead of centuries of religious differences and legacies of imperial oppression and division, it’s clem and the boys becoming domestic terrorists because they’d rather die than go back to the world where they knew shame.”