It's clearly necessary to begin thinking about what form deterrence will take against future terrorist attacks on the U.S. At least 5 such attacks have been prevented at the operational stage by Bush administration policies over the last six years. What is needed is more serious consideration of the value of policies that deter such attacks.

This is likely to become a more pressing concern, as America's ability to interrupt such attacks, if a Democrat becomes President, will be severely eroded. The Democrats are profoundly indifferent to national security, and have even managed to convince themselves that terrorism is some vast right-wing conspiracy. If the Islamists have learned anything from their defeat in Afghanistan and Iraq, it is that they must do whatever it takes to re-establish their beachhead in the U.S. They must bring their war back to their declared target. There can be little doubt the Democrats will give them this opportunity.

Conventional wisdom contends that if a terrorist group conducts a nuclear hit on a major American city, there would effectively be no return address against which to retaliate, making such an attack non-deterrable. Bret Stephens, in his article, "Who Needs Nukes?" (The Wall Street Journal, March 20, 2007), pointedly asks: "Would it hinder Islamist terrorists if the U.S.'s declared policy in the event of a nuclear 9/11 was the immediate destruction of Mecca, Medina and the Iranian religious center of Qom?"

Very likely it would not directly matter a jot to the terrorists. But it would surely make Arab states, their governments, and their people, begin to question the wisdom of whatever levels of overt and/or tacit support is being provided to terror groups. And that would surely hit the terrorists, bigtime.

Stephens continues: "Would our deterrent be more or less effective if we deployed a range of weapons, such as the maligned 'bunker buster', the use of which a potential adversary might think us capable?"

At present the terrorists rely a great deal on Western decency, and the pressure exerted by America's covert enemies in Europe, Canada and elsewhere, restraining the legitimate exercise of American power. Wouldn't the presence of bunker busters in the American arsenal and the stated willingness to use them against terrorist hideouts perhaps have some deterrence value?

Stephens takes his eyes off the ball, however, when he asks: "How would the deployment of a comprehensive anti-ballistic missile shield alter the composition of a credible deterrent?" The ABM shield is intended to deter rogue states seeking to exploit the crisis of a major terrorist attack, by following it up with an attack of their own. Such a surprise attack by China, Iran, North Korea, or a post-Musharraf Pakistan is very plausible.

One of the ignored threats of terrorism is precisely the opportunity it presents for a nuclear or non-nuclear attack by a conventional state actor. A robust capacity to deter such conventional attacks must remain a central plank in America's defense network.

Isn't it possible that its effectiveness against terror attacks has been underestimated? As Max Singer, a colleague of Cold War theorist Herman Kahn, referenced in Stephens' article, once said: "Even nihilists have something they hold dear that can be threatened with deterrence. You need to know what it is, communicate it and be serious about it."