The growing debate on invading Iraq hinges on Saddam Hussein's weapons of mass destruction. Opponents of invasion discount the existing threat by arguing that A) he is not crazy enough to use them against us, and B) if he doesn't use them, what threat are they?
The response to A is we do not know that Saddam is sane enough never to use them against us, and it is not a proposition that we should wish to test by giving him yet more time to acquire them. Saddam has acted with supreme irrationality in the past, from launching a catastrophic war against Iran in 1980 to forfeiting half a dozen opportunities offered to him in 1990 to extricate himself with advantage from Kuwait. In the annals of tyranny and on the scale of capricious savagery, he ranks somewhere between Caligula and Mao. There's not much percentage in counting on the rationality of such gentlemen.
Which brings us to objection B: What use are weapons of mass destruction anyway? Well, we had a quite extraordinary demonstration of their efficacy this summer. Just a few weeks ago, India and Pakistan appeared on the verge of war. It never happened. Not only did the feared war not go nuclear, but it did not even go conventional. Why? Many reasons, but perhaps the most important was, paradoxically, the nukes themselves. India made clear that it would not be the first to use nuclear weapons. Pakistan, however, did not follow suit. "We ... do not subscribe to a no-first-use doctrine," declared Pakistan's ambassador to the U.S.
Why? Simply put, because Pakistan is the weaker party. And the weaker party, if nuclear capable, invariably holds out the threat of nuclear war as a way to deter conventional attack.
Pakistan was saying to India, You have a much stronger army. You could probably launch a war and overrun not just Kashmir but much of Pakistan as well. That is why we built our nuclear arsenal. Of course, we do not want to use it. But if you overrun us, we just might strike first. Think about it.
India did. The iron law of the nuclear age is this: nuclear weapons are instruments of madness; their actual use would be a descent into madness, but the threat to use them is not madness. On the contrary, it is exceedingly logical.
During the cold war, the U.S. also threatened first use of nuclear weapons. The Soviets fielded a huge conventional army that could have overrun Western Europe. The U.S. response was not to match the Soviets with countless tank divisions but to threaten nuclear retaliation against a conventional attack.
This is known as the doctrine of extended deterrence. It is "extended" because it was not American nukes deterring Soviet nukes in protection of the American homeland; it was American nukes extended in their deterrence to provide an umbrella for Europe against nonnuclear attack.
At home, first use provoked protest from the pacifist left, most dramatically against President Reagan, who was portrayed as a nuclear cowboy. This was silly. The doctrine of first use made perfect sense. It kept the peace. It also demonstrated the peculiar utility of otherwise unusable nuclear weapons: to deter a conventional attack.