Since my office answers the phone for Doctors for Disaster Preparedness, it was logical for the caller to ask us, as the World Trade Center lay in ruins, "Where are the [bomb] shelters in Tucson?"

"They're gone."

"How could they be gone?" asked the caller.

"Well, the basements are still there, but they sold all the supplies 10 years ago. Don't you remember?"

The caller admitted that she, like most Americans, hadn't been paying much attention. Most Americans assume that the government of the world's only Superpower is taking care of us, especially now that the Cold War is over. We are shocked at the events of September 11, but they could have been worse, much worse.

This time the holy warriors of the Islamic jihad used an airplane and jet fuel. But they might already have a suitcase nuke or two-possibly hijacked or bought from China, or maybe even sent from Russia with love. Their government allies are feverishly developing long-range rockets. Either crude or sophisticated technology can deliver any of the unholy NBC triad of weapons of mass destruction: nuclear, biological, or chemical.

"Unthinkable," people used to say. No one would be crazy enough to use such a weapon, especially against a country that could retaliate.

Our imagination has just been expanded. What is unthinkable to us is not necessarily unthinkable to everyone, and the assumption that it is makes a perilous foundation for national military policy. I decline to call it "defense."

Defenselessness was explicitly the basis for the Cold War policy of Mutual Assured Destruction (MAD). As long as neither of the two sides could insure against annihilation, we could live in an uneasy stalemate. Measures to protect Americans-civil defense-have actually been called immoral.

Consider what the results of this thinking would have been, had terrorists brought the World Trade Center down with a ground-burst nuke. The soot raining down in Brooklyn would have been radioactive. Many thousands or millions of people in the path of that cloud would have faced a slow, agonizing death over the next few weeks.

Such deaths are preventable, with adequate shielding for adequate time (about 2 weeks on the average). For that reason, the United States once had a civil defense program. It died with John F. Kennedy. President Reagan tried to revive it to some extent, with Gen. Julius Becton as director of FEMA. His successor, George H.W. Bush, had no interest in it. And Bill Clinton went so far as to abolish the Office of Civil Defense within FEMA.

American buildings contain a lot of space suitable for shelters, but thanks to federal policy it is probably not stocked. It's not just lack of funding. Companies such as Boeing that have contracts with the government are actually forbidden to prepare shelter space for emergency occupancy.

State emergency planning centers used to have hundreds or thousands of survey meters and Geiger counters to measure radiation, so citizens could be advised when to take shelter and when it was safe to emerge. These instruments were disposed of or given away years ago and not replaced. Our county kept about half a dozen.

Our government has funded substantial research on protective measures for civilian populations, military facilities, and industry. But Oak Ridge National Laboratory, which conducted most of the studies, got rid of its library away about ten years ago.

Believing that the U.S. government would never have a serious civil defense program, dedicated scientists such as Cresson Kearny conducted research on expedient shelters and radiation monitors that citizens could construct for themselves if they had some warning. For a time during the Reagan years, the authoritative book Nuclear War Survival Skills was distributed to state and local officials at the National Emergency Training Center. Now the book is available only from private sources (it can be downloaded from www.oism.org, while you have power and an internet connection).

In recent years, despite a proliferation of threats, Americans have been progressively stripped of the rudimentary protections they once had. In essence, they are offered as hostages to the MAD theory-which collapses entirely if the hostage-taking is not mutual (and it never was).

If a weapon of mass destruction were used in certain other countries, say Russia, or China, or Switzerland, everyone would head for shelter. All Russians, at least during the Cold War, had required civil defense training throughout their school years and into adulthood. The Moscow subways are shelters equipped with blast doors. It is said that the whole city of Beijing could be evacuated underground in about 10 minutes. Switzerland has NBC shelter for 110% of its population, in all private homes and public buildings, protecting against chemical and biological weapons as well as radiation and blast.

During the Gulf War, many mobile steel shelters with state-of-the-art Swiss air filtration systems were buried in the desert-for the protection of Iraqi soldiers.

While Americans are fascinated with the pile of rubble, our adversaries may be more interested in the picture of Americans streaming over the bridges of Manhattan-on foot. Completely vulnerable to an NBC weapon.

Rhetoric about punishment, and revenge, and retaliation will do nothing to help that picture-quite the contrary. Where are the calls to defend Americans and prepare to save their lives if the warriors of the Jihad escalate the attacks?

American troops willingly put themselves in harm's way to protect their families and their homeland, not to carry on a Jihad. But why should they head for Afghanistan when their families are totally unprotected at home?

Civil defense is the necessary foundation for all defense. The time to start is now.

There are things the federal government could do immediately, at minimal cost. For example:

Dr. Orient, an internist in Tucson, is President of Doctors for Disaster Preparedness, and Executive Director of the Association of American Physicians and Surgeons.