The year 2007 marks the 20th anniversary of South Korea's June 10 civil uprising of 1987, and the 10th year since the 1997 Asian financial crisis. To commemorate these occasions, the Korea Herald published a series of contributions from prominent foreign scholars to analyze the significant changes that Korea has undergone during the past two decades. Shorenstein APARC Director Gi-Wook Shin wrote the op-ed below, on the problems of Korean nationalism.

When the Virginia Tech massacre shook American society, Koreans and Korean-Americans alike nervously responded with a deep sense of collective guilt. Many first-generation immigrants took it upon themselves to apologize for the actions of gunman Cho Seung-hui on the grounds that they all share the same Korean ethnicity (meaning blood).

South Korea's ambassador to Washington, Lee Tae-shik, went so far as to say that the Korean- American community needed to "repent," suggesting a 32-day fast, one day for each victim, to prove that Koreans were a "worthwhile ethnic minority in America." The South Korean government offered to send an official delegation to the funerals of the victims.

This episode may seem bizarre or perplexing to non-Koreans since most ethnicities (including Americans) don't have that strong sense of collective responsibility. Yet this incident well illustrates Korea's psyche, i.e., deeply rooted ethnic national identity, which remains strong today.

Korea has been democratizing and globalizing for the last two decades but neither force has weakened the power of nationalism. On the contrary, it has only become stronger.

How can we explain this phenomenon of persistent ethnic nationalism in a country at the forefront of globalization? Where does such a tradition of collectivistic, ethnic identity come from? What are the positive and negative aspects of ethnic nationalism in Korea? How can Korea, as it is becoming a multiethnic society, deal with it in a globalizing world?

Origins and History

Historically Koreans have developed a sense of nation based on shared blood and ancestry. The Korean nation was "ethnicized" or "racialized" through a belief in a common prehistoric origin, producing an intense sense of collective oneness.

Ethnicity is generally regarded as a cultural phenomenon based on a common language and history, and race understood as a collectivity defined by innate and immutable phenotypic and genotypic characteristics. However, Koreans have not differentiated between the two. Instead, race served as a marker that strengthened ethnic identity, which in turn was instrumental in defining the notion of nation. Koreans are said to believe that they all belong to a "unitary nation" ("tanil minjok"), one that is ethnically homogeneous and racially distinctive from its neighbors.

This sense of ethnic homogeneity, contrary to the popular "prehistoric origin" belief, took root in the early 20th century. Faced with imperialist encroachments, from both the East (Japan) and West, Koreans developed the notion of a unitary nation to show its autonomy and uniqueness. For Korea, which had a long history of political, linguistic, and geographic continuity, the internal issues of political integration or geographic demarcation were less important than the threat of imperialism. Enhancement of collective consciousness and internal solidarity among Koreans against the external threat was more urgent. As a result, the ethnic base or racial genealogy of the Korean nation was emphasized.

Sin Chae-ho, a leading nationalist of the time, for instance, presented Korean history as one of the "ethnic nation" ("minjoksa") and traced it to the mythical figure Tangun. According to him, the Korean people were descendants of Tangun Chosun, who merged with the Puy of Manchuria to form the Kogury people. This original blend, Sin contended, remained the ethnic or racial core ("chujok") of the Korean nation, a nation preserved through defense and warfare against outside forces. The nation was defined as "an organic body formed out of the spirit of a people descended through a single pure bloodline" that would last even after losing political sovereignty.

The need to assert the distinctiveness and purity of the Korean nation grew more important under colonial rule, especially as Japan attempted to assimilate Koreans into its empire as "imperial subjects." The assimilation policy was based on colonial racism, which claimed that Koreans and Japanese were of common origin but the former always subordinate.

The theory was used to justify colonialist policies to replace Korean cultural traditions with Japanese ones in order to supposedly get rid of all distinctions and achieve equality between the two nations. Yet colonial assimilation policy meant changing Korean names into Japanese, exclusive use of Japanese language, school instruction in the Japanese ethical system, and Shinto worship. Koreans resented and resisted the policy by asserting their unique and great national heritage. Yi Kwang-su, a leading figure at the time, claimed that bloodline, personality, and culture are three fundamental elements defining a nation and that "Koreans are without a doubt a unitary nation ("tanil han minjok") in blood and culture." Such a view was widely accepted among Koreans: to impugn the natural and unique character of the Korean ethnic nation during colonial rule would have been tantamount to betraying Koreanness in the face of the imperial challenge of an alien ethnic nation. Ironically, Japanese rule reinforced Koreans' claim to a truly distinct and homogeneous ethnic identity.

After independence in 1945, and despite peninsular division into North and South, the unity of the Korean ethnic nation or race was largely taken for granted. Neither side disputed the ethnic base of the Korean nation, spanning thousands of years, based on a single bloodline of the great Han race. Instead, both sides contested for the sole representation of the ethnically homogeneous Korean nation.

Even today, Koreans maintain a strong sense of ethnic homogeneity based on shared blood and ancestry, and nationalism continues to shape Korean politics and foreign relations. Many ethnic Koreans overseas share this sense of ethnic homogeneity, which can explain the response by the Korean American community to the Virginia Tech massacre.

Prize and Price

Ethnic nationalism has been a crucial source of pride and inspiration for the Korean people during the turbulent years of their nation's transition to modernity that involved colonialism, territorial division, war, and dictatorship. It has enhanced collective consciousness and solidarity against external threats and has served Korea's modernization well. Nationalism is also the underlying principle of guiding the current globalization process in the South.

In the North, ethnic national consciousness offered the grounds for the formation of a belief that Koreans are a chosen people, a position that became the epistemological basis for the juche ideology and the recent "theory of the Korean nation as number one." Ethnic nationalism could also play an integrative role in a unification process, as this self-ascribed identity of homogeneity can serve as the basis for the initial impetus toward unification, if not as the stable foundation of a unified Korea.

At the same time, such a blood-based ethnic national identity became a totalitarian force in politics, culture, and society. Individuals were considered only part of an abstract whole, and citizens were asked to sacrifice individual freedom and civil rights for the collectivity.

Nation was also used as a trump card to override other competing identities as well as to justify violations of human and civic rights in both Koreas in the name of the "nation." The power of nationalism has thus hindered cultural and social diversity and tolerance in Korean society.

The dominance of collectivistic, ethnic nationalism constrained space for liberalism in the public sphere. In its formative years of nation building, nationalism developed in opposition to liberalism and these two ideologies were mistakenly positioned against each other. This historical legacy led to the poverty of modern thought in Korea, including liberalism, conservatism, and radicalism. A lack of a liberal base, for instance, made Korean conservatism highly vulnerable to manipulation by authoritarian leaders.

Ironically, the very belief in ethnic unity has also produced tension and conflict between the two Koreas over the last half-century. The prevailing sense of unity in the face of territorial partition has provoked contention over who truly represents the Korean ethnic nation versus who is at fault for undermining that Korean unity. This battle for true national representation helps to explain highly charged inter-Korea conflict, including the Korean War that killed millions of fellows in the name of "national liberation."

Challenges and Future Tasks

Ethnic nationalism will remain an important organizing principle of Korean society. Neither democratization nor globalization has been able to uproot the power of nationalism. It would thus be wrong and dangerous to ignore or underestimate its power, treating it as a mere myth or something to pass away in due course. At the same time, we can't remain simply content with its current role, either.

Instead, it should be recognized that ethnic nationalism has become a dominant force in Korean society and politics and that it can be oppressive and dangerous when fused with racism and other essentialist ideologies. Koreans must strive to find ways to mitigate its potential harmful effects and use it in constructive manner. In particular, Koreans must promote cultural diversity and tolerance, and establish democratic institutions that can contain the repressive, essentialist elements of ethnic nationalism.

This important task is urgent because Korea, on the contrary to popular perception, is becoming a multiethnic society. Today about a half-million migrant labor workers, with the majority coming from China and Southeast Asia, live in the South. Only a decade ago, the number was less than one hundred thousand. Similarly more than one out of 10 marriages is "international," meaning that the spouse is nonethnic Korean (reaching 13.6 percent in 2005). Considering that the figure was only 1.7 percent in 1994, Korea is fast becoming a multiethnic society.

Despite new realities, however, perception and institutions are slow to change. Most Koreans still have stronger attachment to "ethnic Koreans living in foreign countries" than to "ethnic non-Koreans living in Korea." It is also much easier for a Korean-American who to "recover" Korean citizenship than for an Indonesian migrant worker living in Korea to obtain Korean citizenship. This is true even if the Indonesian worker might be more culturally and linguistically Korean than a Korean-American.

The principle of "bloodline" or jus sanguinis still defines the notions of Korean nationhood and citizenship, which are often inseparable in the minds of Koreans. In its formative years, Koreans stressed the ethnic base of nation without a corresponding attention to its civic dimension, i.e. citizenship. After colonial rule, neither state (North or South) paid adequate attention or made serious effort to cultivate a more inclusive notion of citizenship.

Social institutions that can address issues of discrimination against ethnic non-Koreans (e.g., ethnic Chinese known as "hwagyo") have been overlooked and underdeveloped. The Korean nationality law based on jus sanguinis legitimizes consciously or unconsciously discrimination against foreign migrant workers by explicitly favoring ethnic Koreans.

Korea needs to institutionalize a legal system that mitigates unfair practices and discrimination against those who do not supposedly share the Korean blood. Koreans need an institutional framework to promote a national identity that would allow recognition of ethnic diversity and cultural tolerance among the populace, rather than appeal to an ethnic consciousness that tends to encourage a false uniformity and then enforcing conformity to it.

They should envision a society in which they can live together, not simply as fellow ethnic Koreans but as equal citizens of a democratic polity. In fact, it is only a matter of time before Koreans will face serious challenges living in a multiethnic society (e.g., children of ethnically mixed couples, civic rights of migrant labor workers) that it is unprepared to resolve. Preparing for such challenges through public education and legal institutions won't be an easy task and should be an integral part of democratic consolidation processes that are currently under way.

Discussion of unification is premature and problematic if unification occurs without such adjustments. As the German unification experience shows, a shared ethnic identity alone will not be able to prevent North Koreans from becoming "second-class citizens" in a unified Korea. Even worse, because of higher expectations resulting from a shared sense of ethnic unity, a gap between identity (ethnic homogeneity) and practice (second-class citizens) will add more confusion and tension to the unification process.

All said, Koreans should strive to promote ethnic diversity and cultural tolerance, and develop proper legal institution so that all can live together in a multiethnic or unified Korea as equal citizens of a democratic polity. This task will be all the more important and urgent as Korea consolidates democracy, globalizes its economy, and prepares for national unification.

CISAC awarded honors certificates in international security studies to 14 undergraduates who completed theses on policy issues ranging from speeding up the detection of a bioterror attack to improving the World Bank's effectiveness at post-conflict resolution.

Among the 2006-2007 participants in CISAC's Interschool Honors Program in International Security Studies were award winners Brian Burton, who received a Firestone Medal for his thesis, "Counterinsurgency Principles and U.S. Military Effectiveness in Iraq," and Sherri Hansen, who received the William J. Perry Award for her thesis, "Explaining the Use of Child Soldiers." The Firestone Medal recognizes the top 10 percent of undergraduate theses at Stanford each year, and the Perry recognizes excellence in policy-relevant research in international security studies.

CISAC honors students "can make the world a more peaceful place in several ways," FSI senior fellow Stephen Stedman told students and guests at the honors ceremony. "They can graduate and find jobs of power and influence [and] they can identify real world problems and solve them."

This year's class, which included several double-majors, represented nine major fields of study: biology, history, human biology, international relations, mathematics, management science and engineering, physics, political science, Russia-Eurasian studies. Some students headed to business or policy positions, while others looked forward to advanced studies in law, medicine, biophysics, security studies, or other fields.

"I hope that this is the beginning, not the end, of your contributions to policy-relevant research," CISAC senior research scholar Paul Stockton, who co-directed the program with Stedman, told the students. He added, "In every potential career you have expressed a desire to pursue, from medicine to the financial sector and beyond, we need your perspectives and research contributions, to deal with emerging threats to global security."

Many students expressed interest in realizing that hope. Burton said his aspiration is to attain "a high-level cabinet or National Security Council position to cap a long career of public service in foreign policy."

Katherine Schlosser, a biology major who is headed to Case Western Reserve University for joint MD-master's in public health program, said she hopes to "keep conducting innovative research and to eventually rejoin the international security studies community in some capacity."

The 2007 honors recipients, their majors, thesis titles, advisers, and destinations, if known, are as follows:

Brian Burton, political science
"Counterinsurgency Principles and U.S. Military Effectiveness in Iraq"
Firestone Medal Winner
Adviser: David Holloway
Destination: Georgetown University, to pursue a master's degree in security studies

Martine Cicconi, political science
"Weighing the Costs of Aggression and Restraint: Explaining Variations in India's Response to Terrorism"
Adviser: Scott Sagan
Destination: Stanford University Law School

Will Frankenstein, mathematics
"Chinese Energy Security and International Security: A Case Study Analysis"
Adviser: Michael May
Destination: The Institute for Defense Analyses in Alexandria, Va., for a summer internship

Kunal Gullapalli, management science & engineering
"Understanding Water Rationality: A Game-Theoretic Analysis of Cooperation and Conflict Over Scarce Water"
Adviser: Peter Kitanidis
Destination: Investment Banking Division at Morgan Stanley in Los Angeles

Sherri Hansen, political science
"Explaining the Use of Child Soldiers"
William J. Perry Award Winner
Adviser: Jeremy Weinstein
Destination: Oxford University in England, to pursue master's degree in development studies

Andy Leifer, physics and political science
"International Scientific Engagement for Mitigating Emerging Nuclear Security Threats"
Adviser: Michael May
Destination: Harvard University, to pursue a PhD in biophysics

James Madsen, political science
"Filling the Gap: The Rise of Military Contractors in the Modern Military"
Adviser: Coit Blacker
Destination: World travel; then San Francisco to open a bar

Nico Martinez, political science
"Protracted Civil War and Failed Peace Negotiations in Colombia"
Adviser: Stephen Stedman
Destination: Washington, DC, to serve as a staff member for Senator Harry Reid

Seepan V. Parseghian, political science and Russian/Eurasian studies
"The Survival of Unrecognized States in the Hobbesian Jungle"
Advisor: James Fearon

Dave Ryan, international relations
"Security Guarantees in Non-Proliferation Negotiations"
Adviser: Scott Sagan
Destination: Stanford University, to serve as executive director of FACE AIDS

Katherine Schlosser, biology
"Gene Expression Profiling: A New Warning System for Bioterrorism"
Adviser: Dean Wilkening
Destination: Case Western Reserve University in Cleveland, to pursue a joint medical degree and master's in public health

Nigar Shaikh, human biology and political science
"No Longer Just the 'Spoils of War': Rape as an Instrument of Military Policy"
Adviser: Mariano-Florentino Cuellar

Christine Su, history and political science
"British Counterterrorism Legislation Since 2000: Parlimentary and Government Evaluations of Enhanced Security"
Adviser: Allen Weiner
Destination: Stanford University, to finish her undergraduate degree; Su completed the honors program as a junior.

Lauren Young, international relations
"Peacebuilding without Politics: The World Bank and Post Conflict Reconstruction"
Adviser: Stephen Stedman
Destination: Stanford University, to finish her undergraduate degree; Young completed the honors program as a junior.

On June 2, 2007 at Stanford University, the Southeast Asia Service Leadership Network (SEALNet) hosted a well-attended dinner to celebrate its third year of activity and its plans for social service projects in five Southeast Asian countries in Summer 2007.

SEALNet faculty adviser Donald K. Emmerson kicked off the event by congratulating the students on their accomplishments, talents, and enthusiasm. Leadership coach and author Leng Lim, whose Southeast Asia Leadership Initiative fostered the creation of SEALNet in 2004, gave an inspirational talk to the students who would soon leave for Southeast Asia to implement the network's projects. Other speakers included SEALNet Co-Director and Stanford graduating senior Viet Huynh (Stanford 2007) who was thanked for his commitment and service to the organization since its founding.

SEALNet's agenda for 2007 represents a dramatic expansion from the network's first project in Summer 2005. In that year the students delivered a dozen computers to a youth organization in Ho Chi Minh City, Vietnam, and helped local youths learn how to use them. In Summer 2007 the following projects are planned:

Project Cambodia (Phnom Penh, 19 June - 1 July) empowers young Cambodian performing artists and selected high school students to spread awareness of Khmer traditional performing arts among Cambodian youths.

Project Indonesia (Sekayu, South Sumatra, 26 August - 8 September) promotes earthquake and sanitation awareness among members of a vulnerable rural community.

Project Philippines (Cebu, 18 - 29 June) disseminates attractive media messages to raise local and national awareness of the risk of gastrointestinal illness from worms.

Project Thailand (Krabi, 27 August - 7 September) tackles environmental problems and raises ecological awareness among inhabitants of a tsunami-affected area.

Project Vietnam (Ho Chi Minh City, 19 - 30 June) develops a sustainable vocational English program for street children that can help them get jobs in tourism and other service industries.

SEALNet's goals include:

• Creating a cross-cultural network linking students and professionals interested in social and development issues in Southeast Asia;
• Empowering students for positive social change through service leadership projects and by inspiring other students to become leaders in their own communities.
• Working through community service leadership to help make Southeast Asia more united internally and more engaged internationally.

The BP Foundation has awarded a five-year, $7.5 million grant to Stanford University's Program on Energy and Sustainable Development to support research on modern energy markets. The foundation is funded by BP, one of the world's largest energy companies.

The gift follows the BP Foundation's initial grant of $1.8 million over three years, which was pledged in 2004 in support of the program.

"BP's support has allowed our program to study the world's most pressing energy problems, such as global warming, energy poverty and the prospects for the world oil market," said program director and Stanford law Professor David G. Victor. "In addition to BP Foundation support, we learn from BP's experience as an energy company because they operate in all the markets where we do research--such as in China and India."

"BP Foundation believes the work undertaken at Stanford deals directly with global issues that are key to meeting the world's growing energy needs," said Steve Elbert, chairman of the BP Foundation. "The drive to research and implement strategies to further understand today's energy markets is important work, and we are proud to partner again with Stanford."

The Program on Energy and Sustainable Development, part of the Freeman Spogli Institute for International Studies, concentrates on the legal, political and institutional dimensions of how societies derive value from energy. The BP Foundation grant is part of a rapid expansion of Stanford's research and teaching on energy issues, much of which focuses on the technical aspects of energy systems.

All of the program's research is public and published openly, including on its website (http://pesd.stanford.edu/). The gift from the BP Foundation, as well as all similar gifts to support the program's research, includes special provisions that assure the research program's independence in setting its research agenda.

The agreement with Stanford is one in a series of BP partnerships with universities in the United Kingdom, the United States and China, representing a total commitment of more than $600 million. The program at Stanford complements work on similar topics at Princeton University, Tsinghua University and Imperial College, among others.

Founded in 2001, the Program on Energy and Sustainable Development focuses on the "political economy" of modern energy services--the interaction of political, institutional and economic forces that often dominate energy markets. It collaborates with the Stanford Law School and other university departments and schools, including economics, engineering and earth sciences. About half of the program's resources are devoted to research partnerships in key developing countries, including Brazil, China, India, Mexico and South Africa. Program researchers have examined the emergence of a global business in natural gas, reforms of electric power markets and the supply of modern energy services to low-income rural households in developing countries.

The program's other major sponsor is the Electric Power Research Institute in Palo Alto, Calif., a research consortium that includes most of the world's largest electric companies.

President George W. Bush averted a nasty rift when he agreed in the final hours of the recent G8 summit to "consider seriously" the need to halve the world's emissions of global-warming gases by 2050. Canada, the European Union and Japan had already embraced that goal, leaving America the dirty stand-out. The deeper truth is that these eight industrial countries control.

Only part of the world's emissions, and the industrial activities that cause emissions are slow to change. Coal will be the hardest to tame because it is so cheap and abundant. Many coal-power plants coming online today will still be in service by 2050, and advanced plants that store effluent safely underground won't be used widely for many more decades. The geopolitical hurdles are also high. The plan introduced with much fanfare earlier this month by China, which next year will become the world's top emitter of greenhouse gases, contains nothing beyond what Beijing already had in place. The world, therefore, is in for some warming.

Pessimism about stopping global warming is leading some scientists to wonder out loud if it is possible through "geoengineering" to force the Earth to cool. The idea is not entirely new and is fraught with dangers, but it is likely to get more attention in coming years. At least since the 1950s, weather makers have dreamed of steering clouds and rain to crops (though they failed in practice). From there it was a small step to dreaming on the global scale. Indeed, when the thesis of global warming was first proposed a few decades ago, some analysts envisioned putting mirrors in space or on deserts to deflect a small fraction of sunlight--just enough to offset, crudely, the buildup of warming gases in the atmosphere. These premature plans were wildly costly and faltered also because climate is sensitive to a lot more than just the gross amount of sunlight that warms the planet.

Today's plans are looking more practical, though still fraught with danger. One would spread iron, a nutrient for algae, in the ocean to stimulate photosynthesis, a natural process in which plants absorb carbon dioxide. Injecting iron in parts of the ocean where it is scarce could trigger algal blooms and help remove even more CO2. Experimental "iron fertilization," as well as careful measurement around natural iron sources, offers tantalizing support for the theory, though nobody knows what biological horrors might follow from messing with the ocean ecosystem on a large scale. Nobel laureate Paul Crutzen helped touch off the current pondering about geoengineering with an editorial in the August 2006 issue of the scientific journal Climatic Change. He revived a Russian idea from the 1970s to inject sulfur particles into the stratosphere with balloons, artillery guns or jumbo jets. (Full disclosure: I am on the journal's board of editors.) Sulfur, in turn, can produce aerosols (particulates) and clouds that reflect some sunlight back to space.

The plan has some drawbacks. Nasty chemistry, including that which caused the hole in the ozone layer, might follow--nobody is sure. Sulfur can also cause acid rain and respiratory diseases. But such ideas are worth a close look, says Crutzen, because unchecked changes in climate might be even worse. And nature already does this--through volcanoes such as Mount Pinatubo, which cooled the planet for a while after it erupted in 1991. None of this is ready for prime time, and the mere mention causes environmentalists to shudder because it distracts from the urgent need to reduce emissions. But it will get more attention as the difficulties in making deep cuts in emissions and adapting to climate change become more apparent.

Geoengineering will raise at least two awkward questions. First, it turns the geopolitics of global warming on its head. Cutting emissions requires many nations to cooperate. Geoengineering can be done by just a few, or even one. Who will determine if geoengineering is safe, and what if the rest of us don't like the consequences? The second is humanity's relationship to nature. Climate warming is already causing stress on natural ecosystems, and it is a small step to imagine engineering rare and special ecosystems to help protect them. But if mankind extends management to the whole planet, do we, in effect, turn Earth into a zoo?

The probability of a nuclear weapon one day going off in an American city cannot be calculated, but it is larger than it was five years ago. Potential sources of bombs or the fissile materials to make them have proliferated in North Korea and Iran. Russia's arsenal remains incompletely secured 15 years after the end of the Soviet Union. And Pakistans nuclear technology, already put on the market once by Abdul Qadeer Khan, could go to terrorists if the president, Gen. Pervez Musharraf, cannot control radicals in that country.

In the same period, terrorism has surged into a mass global movement and seems to gather strength daily as extremism spills out of Iraq into the rest of the Middle East, Asia, Europe and even the Americas. More nuclear materials that can be lost or stolen plus more terrorists aspiring to mass destruction equals a greater chance of nuclear terrorism.

Former Senator Sam Nunn in 2005 framed the need for Washington to do better at changing this math with a provocative question: On the day after a nuclear weapon goes off in a American city, "what would we wish we had done to prevent it?" But in view of the increased risk we now face, it is time to add a second question to Mr. Nunn's: What will we actually do on the day after? That is, what actions should our government take?

It turns out that much could be done to save lives and ensure that civilization endures in such terrible circumstances. After all, the underlying equation would remain a few terrorists acting against all the rest of us, and even nuclear weapons need not undermine our strong societies if we prepare to act together and sensibly. Sadly, it is time to consider such contingency planning.

First and foremost, the scale of disaster would quickly overwhelm even the most prepared city and state governments. To avoid repeating the Hurricane Katrina fiasco on a much larger scale, Washington must stop pretending that its role would be to support local responders. State and local governments--though their actions to save lives and avoid panic in the first hours would be essential--must abandon the pretense that they could remain in charge. The federal government, led by the Department of Homeland Security, should plan to quickly step in and take full responsibility and devote all its resources, including those of the Department of Defense, to the crisis.

Only the federal government could help the country deal rationally with the problem of radiation, which is unique to nuclear terrorism and uniquely frightening to most people. For those within a two-mile circle of a Hiroshima-sized detonation (in Washington, that diameter is the length of the Mall; in New York, three-fourths the length of Central Park; in most cities, the downtown area) or just downwind, little could be done. People in this zone who were not killed by the blast itself, perhaps hundreds of thousands of them, would get radiation sickness, and many would die.

But most of a city's residents, being further away, would have more choices. What should they do as they watch a cloud of radioactive debris rise and float downwind like the dust from the twin towers on 9/11? Those lucky enough to be upwind could remain in their homes if they knew which way the fallout plume was blowing. (The federal government has the ability to determine that and to quickly broadcast the information.) But for those downwind and more than a few miles from ground zero, the best move would be to shelter in a basement for three days or so and only then leave the area.

This is a hard truth to absorb, since we all would have a strong instinct to flee. But walking toward the suburbs or sitting in long traffic jams would directly expose people to radiation, which would be the most intense on the day after the bomb goes off. After that, the amount would drop off day by day (one third as strong after three days, one fifth as strong after five days, and so on), because of the natural decay of the radioactive components of the fallout.

More tough decisions would arise later. People downwind could leave their homes or stay, leave for a while and then come back or leave and come back briefly to retrieve valuables. The choices would be determined by the dose of radiation they were willing to absorb. Except in the hot zone around the blast and a few miles downwind, even unsheltered people would not be exposed to enough radiation to make them die or even become sick. It would be enough only to raise their statistical chance of getting cancer later in life from 20 percent (the average chance we all have) to something greater--21 percent, 22 percent, up to 30 percent at the maximum survivable exposure.

Similar choices would face first responders and troops sent to the stricken area: how close to ground zero could they go, and for how long? Few would choose to have their risk of death from cancer go up to 30 percent. But in cases of smaller probabilities--an increase to 20.1 percent, for example--a first responder might be willing to go into the radiation zone, or a resident might want to return to pick up a beloved pet. These questions could be answered only by the individuals themselves, based on information about the explosion.

Next comes the unpleasant fact that the first nuclear bomb may well not be the last. If terrorists manage to obtain a weapon, or the fissile material to make one (which fits into a small suitcase), who's to say they wouldn' have two or three more? And even if they had no more weapons, the terrorists would most likely claim that they did. So people in other cities would want to evacuate on the day after, or at least move their children to the countryside, as happened in England during World War II.

The United States government, probably convened somewhere outside Washington by the day after, would be urgently trying to trace the source of the bombs. No doubt, the trail would lead back to some government--Russia, Pakistan, North Korea or other countries with nuclear arsenals or advanced nuclear power programs--because even the most sophisticated terrorist groups cannot make plutonium or enrich their own uranium; they would need to get their weapons or fissile materials from a government.

The temptation would be to retaliate against that government. But it might not even be aware that its bombs were stolen or sold, let alone have deliberately provided them to terrorists. Retaliating against Russia or Pakistan would therefore be counterproductive. Their cooperation would be needed to find out who got the bombs and how many there were, and to put an end to the campaign of nuclear terrorism. It is important to continue to develop the ability to trace any bomb by analyzing its residues. Any government that did not cooperate in the search should of course face possible retaliation.

Finally, as buildings and lives were destroyed, so would the sense of safety and well-being of survivors, and this in turn could lead to panic. Contingency plans for the day after a nuclear blast should demonstrate to Americans that all three branches of government can work in unison and under the Constitution to respond to the crisis and prevent further destruction.

A council of, say, the president, the vice president, the speaker of the House and the majority leader of the Senate, with the chief justice of the Supreme Court present as an observer, could consider certain aspects of the government's response, like increased surveillance. Any emergency measures instituted on the day after should be temporary, to be reviewed and curtailed as soon as the crisis ends.

Forceful efforts to prevent a nuclear attack--more forceful than we have seen in recent years--may keep the day from coming. But as long as there is no way to be sure it will not, it is important to formulate contingency plans that can save thousands of lives and billions of dollars, prevent panic and promote recovery. They can also help us preserve our constitutional government, something that terrorists, even if armed with nuclear weapons, should never be allowed to take away.

William J. Perry, a professor at Stanford, and Ashton B. Carter, a professor at Harvard, were, respectively, the secretary and an assistant secretary of defense in the Clinton administration. Michael M. May, also a professor at Stanford, is a former director of the Lawrence Livermore National Laboratory.