Shadow of the 'dirty bomb'

A fortnight before Abdullah al-Mujahir arrived in Chicago, senior American officers were taking part in sensitive war games at the Army War College in Pennsylvania. Among the scenarios they were studying: a "dirty bomb", a high explosive blast scattering radioactive material across an American city.

In the exercises, code-named Vigilant Warrior, planners assumed the terrorists would detonate their bomb in a hospital, turning the isotopes used in x-rays and other medical procedures from lifesaving medicine into a contaminant bringing death through cancer to thousands. The hijack of peaceful uses of radiation had been foreseen before the arrest of Mujahir on 8 May by the American intelligence people and military and they were already sensitive to its disturbing implications.

Another simulation, one carried out by the Federation of American Scientists (FAS), projected the chaos, contamination and death resulting from blowing up isotopes used to irradiate food. In this case, the cobalt contamination of a bomb exploded in New York was calculated to extend for 1,000 square kilometres and to have given the entire population of Manhattan a one-in-100 chance of developing cancer.

The bombs in these planning exercises were small and easily concealed, containing about 10lbs of TNT and radioactive substances ranging from a few grammes to a couple of kilos. In other words, this kind of device is a world away from detonating some home-made atom bomb. The materials are easily found, easily concealed and horribly complicated to deal with.

While the immediate casualties from a "dirty bomb" might include only a few deaths, it could leave thousands of victims facing uncertain health and contaminate the centre of some great city to levels that would ensure its long-term evacuation. As the head of the FAS told Congress, "these areas would have to be abandoned for decades".

It is the spectre of people being banned from Trafalgar Square or the Champs Elys?es for a generation that is perhaps the most worrying aspect of this type of terrorism. The financial cost would be colossal and the psychological blow to a nation immense.

The scientists and intelligence people who have investigated this kind of weapon know that using one would actually be a rather low-end tactic for al Qaeda. Indeed, if the American claims about the plot are proven in court, then the type of attack planned by Mujahir, and indeed its choice of operative, could be seen as evidence of how far the organisation has been suppressed.

A year or two ago, after all, bin Laden was courting top Pakistani nuclear scientists and trying to buy former Soviet nuclear weapons. With one of those, he could have wiped out hundreds of thousands. Documents found in Afghanistan after the fall of the Taliban showed that Osama bin Laden's organisation-also had ambitions to build its own atomic bomb.

Mujahir, like the British "shoe bomber" Richard Reed, was born a non-Muslim. Both men converted in jail. Both stood out with their western passports - Mujahir as he was trained in Pakistan and Reed when he met militants in Gaza. Their use may also be seen as something of a sign of desperation on the part of al Qaeda.

So the chosen operative and the methods of attack, while potentially lethal, were not impressive for an organisation that once had more apocalyptic ambitions. In fact, the "dirty bomb" is a weapon basic enough to be available to isolated groups of fanatics like the Americans who carried out the Oklahoma bombing.

As for the lasting impact of the "dirty bomb" plot, it is to further heighten American anxieties about their vulnerability to terrorism. Last autumn's anthrax release (whoever was responsible for that) showed how even an attack with very limited loss of life could produce widespread terror.

It is the contaminant of uncertainty and insecurity that has now been released into the American political atmosphere, producing a general acceptance of tough antiterrorist methods.

The defensive side of the administration's policy is well illustrated by new immigration restrictions, basically designed to keep closer tabs on Arab visitors.

The howls of protest from civil rights and Arab-American groups have cut little ice with Middle America, for the average citizen buys the idea, post 9/11, that greater scrutiny will have to be exercised on those who abused the open nature of American society in attacking the World Trade Center and the Pentagon.

Abroad, the insecurity produces support for the interventionist policies announced recently by President Bush. Those who sit in the salons of Europe talking about the disconnection between Osama bin Laden and Saddam's Iraq are missing the point. No connection is required beyond the knowledge that the vast majority of Americans now believe in dealing with problems aggressively, rather than hoping - as the previous Administration often seemed to with both al Qaeda and Iraq - that they will go away on their own.

For America now, the words "weapon of mass destruction" and " terrorism" are sufficiently linked for tough action to be demanded against any state having much of a connection with either. Inevitably, most of these new enemies are Middle Eastern countries.

There has been a definite sense in the recent statements and leaks about imminent terrorist attacks that decision makers in Washington know their chances of frustrating another 9/11 are 50/50 at best. The non-specific warnings, the changed immigration rules and the news of Mujahir's arrest all seem to carry a message of "we're doing everything we can, don't blame us if something terrible happens".

It all serves to remind Americans that they are engaged in a war of some sort - one where the infringement of certain civil liberties or international niceties is imperative. Many Europeans seemed to forget that, even after last September, and this difference of perspectives just makes it harder to keep the old allies united around a common purpose.