Brian Michael Jenkins, Will Terrorists Go Nuclear? (New York: Prometheus Books, 2008), 457 pp., $26.95.

BRIAN JENKINS does not think we, as a nation, should ignore the risks associated with a nuclear terrorist attack. He does not believe the consequences would be trivial. He thinks we ought to take specific steps to reduce the likelihood of such an event occurring. But he also thinks that the probability of a nuclear terrorist attack is lower than "expert" estimates, that these estimates create an atmosphere of terror, that deterrence is still a useful defense against the threat, that by planning we can reduce the effects of an attack if it occurs, that we should stop hyping the threat and putting our civil liberties at risk, and that, in general, we ought to be less hysterical in our approach to nuclear terrorism.

In short, he sounds like the experienced field operative turned cold, calculating analyst of terrorism that he is. Jenkins seeks to overturn the emerging conventional wisdom of what constitutes the greatest threat to American security, and his arguments cannot be dismissed. But to what extent they ought to be embraced and genuinely cause us to revise our risk assessment about nuclear terrorism is a fair and important question of national security. Or, as President Bush is supposed to have asked simply, "How real is this nuclear terrorism thing?"

Jenkins's major complaint in his new book, Will Terrorists Go Nuclear?, is that experts, government officials and the media together have made Americans the victim of nuclear fears by exaggerating the likelihood of a nuclear terrorist event occurring, overstating the impact such an event would have, and injecting emotion and hysteria into the national-security discourse on the subject. He quotes academics, respected national-security experts and senior government officials who have pointed to nuclear terrorism as the greatest threat facing the nation in the post-9/11 world. He refers to popular television shows and movies that moved from dramatizing a superpower nuclear exchange during the cold war to plots involving stolen or improvised nuclear devices during the war on terror. After discussing former-CIA Director George Tenet's deep concern about a nuclear terrorist attack, described in a book Tenet wrote after leaving office, Jenkins quotes Vice President Dick Cheney in an interview on Face the Nation last year: "The threat to the United States now of . . . a nuclear weapon in the middle of one of our own cities is the greatest threat we face. . . . It's something we have to worry about and defeat every single day."

The net effect of all the hype, Jenkins argues, is that al-Qaeda is "the world's first terrorist nuclear power without, insofar as we know, possessing a single nuclear weapon," and Americans are the victims of nuclear terror without ever having experienced any act of nuclear terrorism.

What we want to know, of course, is whether the author has it right. Jenkins, who has been studying and writing about terrorists and terrorism for more than thirty years, knows what he is talking about when he dissects the motives of and self-imposed constraints on terrorists. His chapters on terrorists are extremely well-written and informative surveys aimed at placing the nuclear terrorist act in the proper context. He has good and bad news for us. The good news is that at least some terrorist groups who might try to get their hands on a nuclear weapon would not want to detonate it, making a calculation similar to that of a national government: better to have and to hold for deterrence. The bad news is that terrorist groups whose motivation is not so secular, and is better described as divine or apocalyptic-think Aum Shinrikyo or al-Qaeda-would not be satisfied with mere possession and would likely aim to use a bomb in order to commit mass murder. The principal bit of comfort he has to offer about that prospect is that the technical and organizational capability to carry out all the complex steps involved in acquiring, delivering and detonating a nuclear weapon seem least likely to be present in those groups who actually want to cause mass civilian casualties. While an interesting insight, it is not one that we are advised to depend on: things change.

Most of Jenkins's argument rests on the difficulty of actually acquiring a nuclear device, and on the limited destructive force of an improvised weapon built by terrorists. On the latter point, he writes:

From the 1990s on, and especially since 9/11, the discussion of nuclear terrorism has been taken over by policy makers, most of whom possess little knowledge of technical matters. They are backed up by a press that tends to be somewhat ignorant of science, and by what one critic called the "terrorism industry."

Here the author seeks to explain why the threat, typically characterized by scientists in the 1970s as the detonation of a device with a yield of a few tenths of a kiloton, was upgraded to an explosion-one-hundred-times greater-of a Hiroshima-sized, ten-kiloton bomb in the 1990s. This is the difference between bringing down a skyscraper with the equivalent of one hundred tons of TNT and obliterating a large portion of a city with the equivalent of ten thousand tons of TNT. To underline his point, he notes that a couple of years ago the North Koreans could manage only to detonate a half-kiloton-yield device.

Ultimately, though, the size observation is not really reassuring. There are just too many variables involved, and ignorance on the part of the current generation of analysts is not the most important one. It is certainly arguable that if terrorists manage to get their hands on enough highly enriched uranium, rather than plutonium, and the overall size of the whole bomb package was not limited by the requirements of the method of delivery, there is enough information available these days for a terrorist organization to make a bomb of the simple "gun type" design and yield used at Hiroshima. If true, this would make the higher-yield city-buster quite plausible, even assuming no special knowledge of nuclear-explosive design. However, it would require some expertise in nuclear engineering, high explosives and metallurgy. Moreover, drawing conclusions from first attempts at nuclear explosions using plutonium and the more technically demanding "implosion" design, whether by India or North Korea, may not be particularly relevant, especially when we are uncertain about those governments' intent, or "design yield."

Having said that, the crux of the matter is neither yield nor motive, but if we really should be so worried about a terrorist building or otherwise acquiring a nuclear weapon. Those of us who have spent a good portion of our professional lives-more than Jenkins would think appropriate-worrying about this threat tend to view any scenario involving the acquisition of a fabricated nuclear weapon as far less likely than one that has the terrorists acquiring fissile material and building one. (No one, for good reason, thinks terrorists will be able to produce their own fissile material.) While the acquisition of a fabricated weapon cannot be excluded as a possibility and is featured in the plots of movies and novels, governments are, in fact, less likely to "lose" one of their weapons from an arsenal than they are some kilograms of fissile material from their research, energy or weapons establishments. They are also less likely to contemplate transferring a fabricated weapon to a terrorist group, because it could more easily be traced back to them than could fissile material, whose origins, our best efforts at nuclear forensics notwithstanding, might be hard to determine with any certainty.

So, much of what is at issue here comes down to the plausibility of terrorists acquiring the necessary fissile material and building a true nuclear weapon. This is because delivery-while not a trivial matter for a package expected to be large and heavy, of substantial mass, with some radioactive signature-is usually not singled out as a comparable obstacle, at least not by those at all familiar with the challenges of securing America's borders.

The fissile material would have to be acquired by transfer from a country whose government had approved its movement, or as the result of theft from a country whose government had not authorized its movement. Jenkins disparages the former, state-sponsored nuclear terrorism and, indeed, this would seem the less likely scenario. However, current concerns that North Korea and Iran might do just that should not be dismissed too rapidly. The regime in Pyongyang has a record of transferring extended-range-ballistic-missile technology, equipment and more to the Middle East and South Asia, creating a medium-range-ballistic-missile threat for the delivery of nuclear weapons in countries where one did not exist before. North Korea is the only country on earth still in this business. Moreover, the best information currently available suggests that the North Koreans built a plutonium-production reactor in Syria, a well-known sponsor of terrorism, that would be providing that country with a shortcut to nuclear weapons were it not for Israel's concept of nonproliferation. As for Iran, while it now has no source of fissile material, it is busy building facilities that will give it the capability to produce both highly enriched uranium and plutonium. From the American perspective, Iran is now the world's most active supplier of advanced conventional weapons to terrorist groups operating in the Middle East. So, assuming that Tehran will act responsibly if it acquires fissile material would seem to involve more optimism than is justified by experience.

What worries the worriers most, however, is theft-either from Russia, where there is still much plutonium and highly enriched uranium inadequately secured, or Pakistan, where both varieties of fissile material are produced and whose security has been, and will continue to be, at risk. Jenkins, unfortunately, does not take on this most likely of scenarios. Instead, he devotes one chapter each to discussion of the probably mythical red mercury and supposedly lost Russian suitcase bombs. He largely dismisses both, and he is almost certainly correct to do so.

Virtually every chapter in the book has something of value, usually an argument structured to diminish some part of the case for, or assumption essential to, the nuclear terrorist threat. He is careful not to dismiss the case or the assumption, but he often does a credible job of crippling them. Take the chapter entitled "Is Deterrence Dead?"

Jenkins begins where most discussions of deterrence of terrorism end, with a quote from the former head of the United States Strategic Command: "How do you deter or dissuade someone whose reward is in the ‘after life'?" Jenkins does not take the question to be rhetorical. First, he observes that while martyrdom may appeal to individual terrorists, the terrorist group has a kind of rationality and thus will want to do things it regards as successful-and be around afterward to continue doing them. Thus we should realize that "a society's demonstrable resiliency contributes to deterrence." Spelling this out, Jenkins observes:

Terrorists will never have enough nuclear weapons or sufficient destructive power to destroy an entire country. More likely, their arsenal will be limited to one or two low-yield devices. The losses would still be tragic, but the republics will survive-wounded, angry, determined, and very dangerous.

The reader can see where this is going. Jenkins reminds us of the losses our country has survived, from world wars to the devastating flu of 1918: if we do not see our defeat in the terrorists' act, they cannot see their own victory and may thus be deterred from this high-risk/low-payoff course of action. Further, "terrorists and their supporters must be helped to understand" that our "pursuit of transgressors would be relentless," that there would be "no respite, no forgetting, no quarter" and that Washington would likely "lower the standards of evidence, presume guilt, violate sovereignty, attack preemptively." Then, lest his enthusiasm for a deterrent response scare us as well as the terrorist, he adds, "Ruthless pursuit does not, however, mean indiscriminate violence or other actions inconsistent with core American values."

This sounds like the kind of posture we are in right now following our moves into Afghanistan and Iraq and our pursuit of the al-Qaeda leadership after 9/11. But, after all this, is there any good reason to believe that Osama bin Laden and al-Qaeda are deterred from attempting a nuclear terrorist attack? That is meant to be a rhetorical question.

Perhaps the most intriguing chapter in the book is one that plays out, with dialogue, what the debate would be like in the White House if a nuclear weapon were to be detonated in New York City. Senior officials debate pressing questions: Should other cities be evacuated? Should we attack Iran? What are the Russians, Israelis and South Asians likely to do? Jenkins does a good job of capturing the decision makers' need for information that would not be available, the need to do something while avoiding doing the wrong thing, and the inevitable confusion and hysteria that would be injected into a debate that would have to expand to take account of events around the world prompted by the crossing of the nuclear threshold. Jenkins's reaction to his own well-drawn scenario continues to press his central point, that nuclear terrorism is an "if" not a "when," and that while the probability of its occurrence is only a guess, the reality of our fear of its occurrence is with us now, with all its own unfortunate consequences.

In the end, Jenkins concludes that we should, well, grow up:

We can behave like frightened sheep, content to fill our stomachs while we are herded about by terrorists and cynical politicians who would chip away at our liberty. Or we can behave as citizens whose first mission is to defeat the tyranny of terror.

There is nothing wrong with taking a cold, hard look at the new conventional wisdom that nuclear terrorism is the single-greatest threat confronting our country. There is certainly every reason to resist unnecessary infringements on our civil liberties justified by perceptions of the threat. And we can easily embrace the author's practical recommendations to control fissile material, go after terrorists and be prepared for "the day after" if it occurs-all steps advanced by those analysts and cynical politicians Jenkins decries. But where does that leave us? The truth is that the nuclear terrorist threat has the standing it now does because other cold, hard analysts can see motive in terrorists who have struck us before and are still around, because scenarios for a successful attack are judged to be more than "just possible," because there is neither defense nor deterrent available in which we should have confidence, and because a single detonation would likely devastate a city and several detonations could well devastate the country.

Jenkins is right to note that, in spite of all the hype, a nuclear terrorist attack has not yet happened. It is true that there is only a very, very small chance that an American city will be attacked with a nuclear weapon by terrorists this year or next. But what is the likelihood of such an attack over the next ten or fifteen years if Russian fissile material is not better secured, if Pakistan's political situation is not stabilized, if North Korea and Iran are not prevented from accumulating fissile material, if we do not avoid the widespread use of fissile material in our nuclear-power programs and if we do not break the back of the most capable terrorist organizations? It is that kind of question-one that takes account of our long-term vulnerability-that has led many reasonable observers to make the assessment that this threat is the primary one we will face in the years ahead.

Robert L. Gallucci is the dean of Georgetown University's Edmund A. Walsh School of Foreign Service.