As was pointed out by Tom Friedman, one point of view about Nuclear Deterrent, is that you can could on the other side loving life as much as you do and that you can trust the other side not to commit suicide in an attempt to destroy. Which is quite different from terrorism, where, the other side hates you so much that they don't value their own lives. Now imagine that the other side gets their hands on something like the Tsar Bomba and set it off in a way where there are no winners.
Someone once asked Einstein what he thought World War III would we fought with. He reply from the quotations page was
I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.That's poignant!!