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Weapons of Mass Destruction


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

The dangers posed by weapons of mass destruction have come to occupy center stage in international politics. The term "weapon of mass destruction" (WMD) is used to characterize a variety of weapons that share two key features: their potential for large-scale destruction and the indiscriminate nature of their effects, notably against civilians. There are three major types of WMD: nuclear weapons, chemical warfare agents, and biological warfare agents. In addition, some analysts include radiological materials as well as missile technology and delivery systems such as aircraft and ballistic missiles.
While the mass killing of human beings is not a new feature of warfare, weapons of mass destruction (WMD) pose an unprecedented constellation of challenges to peace and security. Over the past century, various states have built and stockpiled lethal arsenals of nuclear, chemical, and biological weapons and the materials to produce them. While states have officially committed to eliminating all stockpiles of chemical weapons and offensive biological weapons and to strive for the elimination of nuclear weapons, nine countries currently possess nuclear weapons - Britain, China, France, India, Israel (assumed), North Korea (claimed), Pakistan, Russia, and the United States - and several states are believed to possess chemical and/or biological warfare agents.

In addition to the dangers posed by existing stockpiles of WMD, significant problems arise from the spread (or "proliferation") of WMD and related technologies to additional countries, nongovernmental actors, and non-state terrorist networks through clandestine programs and black-market sales of weapons and related technologies. Fears of the terrorist use of WMD increased in the United States and around the world following the terrorist use of the biological warfare agent anthrax in the U.S. mail in 2001 and evidence seized by U.S. forces in Afghanistan that Al Qaeda was actively seeking nuclear materials. 

The use of WMD by terrorists is generally viewed by security officials as a "worst case" scenario and thus attracts paramount concern. As former Secretary of Defense William J. Perry warned at a meeting of the National Academy of Sciences in 2004, "I have never been more fearful of a nuclear detonation than now… There is a greater than 50 percent probability of a nuclear strike on U.S. targets within a decade." Linton Brooks, a top ranking security official in the Bush administration, recently reported to Congress in March 2005 that: "The convergence of heightened terrorist activities and the associated revelations regarding the ease of moving materials, technology and information across borders has made the potential of terrorism involving weapons of mass destruction (WMD) the most serious threat facing the Nation. Preventing WMD from falling into the hands of terrorists is the top national security priority of this Administration."

Despite the inevitable uncertainty surrounding any effort to assess the myriad threats associated with WMD, experts are unanimous in their conviction that we face grave risks that are likely to increase as time goes on, barring fundamental changes in current policies at the local, national and international level. Yet beyond this broad consensus, a wide gulf remains between critics and supporters of current U.S. government policies concerning the U.S. nuclear stockpiles and strategies for WMD non-proliferation.

One such critic, former Secretary of Defense Robert McNamara, stated in May 2005 that, ''If I were to characterize US and NATO nuclear policies in one sentence, I would say they are immoral, illegal, militarily unnecessary, very, very dangerous in terms of the risk of inadvertent or accidental launch and destructive of the nonproliferation regime that has served us so well." In contrast, senior Bush administration officials defend current U.S. nuclear policy and cite a variety of steps the government has taken to reduce the number of strategic nuclear weapons, tighten nuclear security, and dismantle U.S. and Russian warheads, as well as various ongoing programs of cooperative threat reduction and support for the peaceful nuclear cooperation programs overseen by the International Atomic Energy Agency (IAEA), the United Nation's nuclear watchdog agency.

This section of the PAWSS website offers in-depth information on the basic characteristics and current threats posed by nuclear, biological, and chemical weapons. It reviews their history, significant governmental policies and international agreements, and promising strategies to reduce the dangers of these deadly weapons. For example, just one percent of the current U.S. defense budget could provide enough funds to secure all the nuclear bomb material in the world, removing it from the black market for good. Also included are a selected bibliography and additional useful links for further exploration.


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

Although the term WMD provides a convenient shorthand for mass-casualty weapons, there are very important differences in the characteristics, effects and military roles of various nuclear, chemical, and biological weapons.

Nuclear weapons stand apart in the public imagination because of their horrific and unmatched destructive power: an all-out nuclear attack could annihilate billions of people within hours. For this reason, some argue that nuclear weapons should be distinguished from all other types of weapons of mass destruction. There are approximately 30,000 nuclear weapons in national stockpiles of the eight nuclear weapons states: Britain, China, France, India, Israel (assumed), North Korea (claimed), Pakistan, Russia, and the United States. Depending upon the yield and atmospheric conditions, a large thermonuclear weapon dropped on a densely populated city could kill millions of people in an instant. The detonation of just one "small" nuclear weapon could kill as many as 100,000 people. In addition, many thousands more would die over time due to the lethal effects of radiation. Currently, the United States and Russia maintain several thousand nuclear weapons on hair-trigger alert, or what is termed "launch-on-warning" of a nuclear attack.

Because of governmental secrecy, it is impossible to give exact figures on the makeup and yield of global nuclear arsenals. But much is publicly known. An estimated 13,470 nuclear weapons are deployed worldwide by eight countries, with another 14,000 weapons held in reserve, according to the 2005 edition of the SIPRI Yearbook, published by the Stockholm International Peace Research Institute. Overall, the total number of nuclear weapons has decreased in the past few years, yet all eight nuclear weapon states continue to maintain and modernize their arsenals and assert (either publicly or covertly) that nuclear weapons play a crucial role in their national security. It is believed that China does not keep its nuclear force on alert status and that Britain and France maintain their nuclear forces on lower levels of alert. There is incomplete and contradictory information available on the nuclear stockpiles of India, Pakistan and Israel. Most experts believe that the nuclear weapons in these countries are only partially deployed. Even greater uncertainty surrounds the status of North Korea's nuclear program, but some analysts estimate that North Korea may have already built as many as 13 nuclear weapons.

Many aspects of the current nuclear predicament were accurately foreseen in the immediate aftermath of the U.S. Manhattan Project that initially developed the first atomic bombs. Physicist J.R. Oppenheimer, who headed the scientists' efforts in this top-secret program wrote in 1946 that:

The truly radical character of atomic weapons lies neither in the suddenness with which they emerged from laboratories and the secret industries, nor in the fact that they exploit an energy qualitatively different in origin from all earlier sources. It lies in their vastly greater powers of destruction, in the vastly reduced effort needed for such destruction. And it lies no less in the consequent necessity for new and more effective methods by which mankind may control the use of its new powers.

Chemical and biological weapons also pose the terrifying potential of inflicting mass casualties. But there are some very significant differences in their properties, effects, and methods of delivery.

Chemical weapons are notable because of the widespread and longstanding commercial and military experience in manufacturing their constituents. Especially compared with nuclear weapons, chemical weapons are considerably easier and cheaper to manufacture. Many dangerous chemical constituents and so-called precursors of chemical weapons are currently commercially available. An international agreement banning chemical weapons, the Chemical Weapons Convention (CWC), entered into force in 1997. The treaty requires signatories to destroy existing stockpiles of chemical weapons and, as of the end of 2005, at least 2 million chemical weapons and 12 million metric tons of chemical agents have been destroyed and 175 countries have signed on to the agreement.

Biological weapons, which make use of lethal bacteria, viruses, or toxins, are distinguished by their profoundly uncontrollable nature: once unleashed, a biological agent such as smallpox can spread quickly to cause an epidemic in human populations. Although biological weapons are highly dangerous, they have only rarely been used in war or in terrorist attacks. There are growing concerns, though, about the likelihood of future use of biological weapons in light of the dynamism of biomedical technology and advances in the field of biotechnology. The technologies available to create and disperse biological agents are becoming more sophisticated and widely available.

Several countries have developed and maintained active biological weapons programs, despite the fact that the 1925 Geneva Convention prohibits the use of germ weapons in war and the 1972 Biological Weapons Convention (BWC) prohibits states from developing, retaining, and transferring these weapons. Unfortunately, the current ban on offensive biological warfare does not have any enforcement mechanisms, such as international inspections or rules governing research and development of possible bioweapons like anthrax. Negotiations to establish mechanisms to verify compliance and assure enforcement of the ban on offensive biological weapons have been unsuccessful; the most recent effort broke down in 2002 because the United States refused to allow biological weapons inspections on its soil.

Useful Links

The Nuclear Threat Initiative offers a comprehensive overview and primer on WMD, including analyses, news updates, and country profiles.

The Arms Control Association offers excellent resources on a wide variety of issues pertaining to WMD, including an overview of key arms control agreements and analyses of timely issues.

A thorough overview and chronology of key developments on WMD, as well as a listing of educational resources, is available from the Center for Nonproliferation Studies, part of the Monterey Institute for International Studies.

For interactive resources and information on the history and science of nuclear weapons, including a useful glossary of terms, see the Atomic Archive Website, supported by the National Science Foundation.

The Carnegie Endowment for International Peace provides a comprehensive website that includes an assessment of weapons, updates on proliferation concerns, and useful links.

Extensive resources and a chronology of the nuclear age are available at the website of the Nuclear Age Peace Foundation,

An international consortium of research institutes provides a variety of updates and analysis on cooperative efforts to reduce the threat of WMD, under the auspices of
Strengthening the Global Partnership, through the Center for Strategic and International Studies.

Data and analysis of trends and developments in military expenditures and arms production worldwide can be found at the website of the Stockholm International Peace Research Institute:


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

Today, a handful of nations possess an inventory of about 30,000 nuclear weapons, roughly half the number that existed at the height of the Cold War. On average, these weapons each possess an explosive power 20 times greater than the nuclear weapons that destroyed much of Hiroshima and Nagasaki in Japan and killed roughly 250,000 people during World War II. Since 1945, no nuclear weapon has been used in a conflict, even though combatants—including nuclear weapons states—have fought approximately 100 wars in the intervening 60 years.

Meanwhile, though, because nuclear weapons have been a part of state arsenals for more than half a century, there is a tendency among policymakers toward tacit acceptance about these weapons that can, in itself, be dangerous. Manhattan Project scientist Wolfgang Panofsky noted recently in a presentation commemorating the 60th anniversary of the first nuclear test, that nuclear weapons have increasingly come to be seen by some as: "symbols of strength and prestige, and tools for diplomatic bargaining. Some decision makers are even searching for new missions where conjectured circumstances might give advantages to nuclear weapons over conventional munitions." Such efforts, risk endangering the longstanding taboo against the use of nuclear weapons.

How Nuclear Weapons Work

Nuclear weapons, like conventional bombs, are designed to cause damage through an explosion that releases a large amount of energy in a short period of time. In conventional bombs, the explosion is created by a chemical reaction, which involves the rearrangement of atoms to form new molecules. In nuclear weapons, however, the explosion is created by changing the atoms themselves, either by splitting them or fusing them together to create new atoms.

The amount of energy released in such a nuclear reaction is enormous—many orders of magnitude greater than that released in a chemical reaction resulting in the rearrangement of molecules. The amount of energy available within an atom is given by Einstein's famous formula E=mc2, where E = energy, m = the mass and c = the speed of light. Thus the energy available equals the mass multiplied by 9,000,000,000,000,000,000 (or the square of the speed of light represented in meters per second). As a result, a nuclear bomb using one kilogram of plutonium could have the same explosive force as approximately 15 million kilograms of the conventional explosive TNT.

As indicated above, there are two main types of nuclear weapons: fission weapons and fusion weapons.

Fission weapons: In fission weapons, atoms are split. The core of a fission bomb is made of either plutonium or highly enriched uranium. Plutonium and uranium atoms are both heavy, meaning they have a large number of protons and neutrons in the nucleus. During fission, when the heavy nucleus splits into two smaller nuclei, extra neutrons are released. If these neutrons are absorbed by other nuclei, they can, in turn, split, also releasing neutrons and setting off what is known as a chain reaction. Plutonium or highly enriched uranium are the only materials known that can, under carefully designed circumstances, achieve such a devastatingly powerful, self-sustaining fissile chain reaction.

Fusion weapons: In fusion weapons—often known colloquially as hydrogen bombs—deuterium and tritium, two isotopes of hydrogen, are fused together to create heavier atoms. This is the same reaction that occurs in the center of the sun. Fusion can only happen at extremely high temperatures and pressure. In a fusion weapon, such a state is created by using a fission explosion (i.e. an atom bomb) to trigger the fusion reaction. There is no theoretical limit to the explosive force of a fusion weapon. Typically, fusion weapons are 10 to 100 times as explosive as the fission bombs dropped on Hiroshima and Nagasaki.

Effects of Nuclear Weapons

To understand the effects of a nuclear weapon, it is important to realize that a nuclear explosion produces several distinct forms of energy that each has its own devastating set of consequences: blast, thermal radiation, electromagnetic pulse, direct nuclear radiation, and fallout.

Blast: The rapid release of energy in an explosion creates a shock wave equivalent to several thousand pounds of pressure per square inch (psi), enough many times over to crush most objects on earth. By way of comparison, brick houses and human lungs can be crushed at about 30 psi pressure or less.

Thermal radiation: Thermal radiation includes heat and light. The heat from a nuclear explosion is so intense that nearly all materials at the center of the explosion (epicenter) are immediately vaporized. The thermal radiation also creates a fireball which rapidly expands outward, consuming oxygen and, combined with the blast effect, creating near total destruction for some distance from the epicenter. Meanwhile, the light produced by a nuclear explosion can be seen from hundreds of miles away. The radius of the flash depends on the power of the weapon and the atmospheric weather conditions. Generally, however, the light is so intense it can make sand explode, blind people many miles away, burn shadows into concrete, ignite flammable materials at large distances, and burn human skin.

Electromagnetic pulse: In addition to its other effects, a nuclear explosion sends out an electromagnetic pulse, similar to the thermal pulse. Although the electromagnetic pulse does not directly harm humans, it can increase the devastation at the site of a nuclear explosion because it disables all electrical devices in its path, including computers, communication and medical devices.

Direct nuclear radiation: A nuclear explosion releases several forms of radiation. Both gamma rays and neutrons easily penetrate solid objects and can be deadly. Beta and alpha particles are generally less dangerous, having much shorter ranges - several meters and several centimeters, respectively. Alpha particles cannot penetrate human skin. If ingested, however, alpha particles will cause the most damage to the human body.

Fallout: Fallout consists of large numbers of particles, from the earth, buildings and other ground objects, which are propelled upward in the blast and irradiated, mixing with the radioactive products of the explosion. Some of this material will fall back to earth within a few minutes, and radioactive fallout may continue its descent for about 24 hours. The rising and descending debris forms the mushroom cloud that follows a nuclear explosion. The distribution of fallout depends on the topography of the land and weather conditions, especially the direction and speed of winds. Radioactive fallout may travel and settle in areas hundreds of miles from the explosion site.

Radioactive fallout may be the most insidious effect of a nuclear explosion because the area of exposure to fallout is much wider and more unpredictable than that of direct nuclear radiation. Its removal is a costly and dangerous job. And, because there is no known way of neutralizing radioactive fallout, it will remain dangerous until the individual radioactive particles have decayed to such an extent that they no longer emit significant amounts of radiation—a period that can last thousands of years.

Effects of Radiation on Humans

The effects of radiation on the human body vary, depending on the dosage of radiation and whether exposure is slow and protracted or large and instantaneous.
Radiation affects those cells in the human body that actively divide, such as those found in hair, in the intestinal tract, in bone marrow, and in the reproductive organs. A large, rapid dose of radiation causes cell death, and effects are apparent within hours, days, or weeks. With protracted exposure, however, cells can do some repair over the exposure period. Radiation doses low enough to avoid cell damage can still induce cellular changes that may be clinically detected sometime in the future, and can potentially be passed on through mutated or defective genes.

The most serious delayed, long-term effect of radiation exposure is a significantly increased incidence of leukemia and thyroid, lung, breast, and bone cancers. The incidence of a particular type of cancer depends on how the radiation exposure occurs. For example, uranium mine workers display a high incidence of lung cancer from inhaling radioactive dust. Workers who painted glow-in-the-dark radium onto watch faces at the turn of the century licked their radioactive paintbrushes, leading to a high incidence of bone cancer and radiation-induced anemia. There is also a very high incidence of leukemia among Hiroshima survivors. These victims also suffered from high incidences of cataracts and hair loss, as well as increases in infertility and birth defects.

Note: The summaries above are compiled from the following sources where additional information can be found.

For an introduction to atomic physics and nuclear weapons effects, see:

For information on nuclear weapons and weapons facilities worldwide, see
The Nuclear Notebook, which includes updates of global nuclear arsenals by Robert S. Norris and Hans Kristensen, suppoted by the Natural Resources Defense Council (NRDC), an environmental NGO.

For a description of types of nuclear weapons, their effects, and global stockpiles, see:

The Federation of American Scientists website offers a helpful overview of nuclear weapons and technology.

The Nuclear Weapon Archive, an offshoot of the Federation of the Atomic Scientists website, provides information and technical data on the history of nuclear weapons.

For a discussion of the history of nuclear weapon-related accidents, see the website of the Center for Defense Information, an independent research organization based in Washington, D.C.


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

On August 6, 1945, in the final stages of World War II, the United States dropped the first atomic bomb on Hiroshima, Japan. A second atomic bomb was exploded over the Japanese city of Nagasaki on August 9, 1945. The advent of nuclear weapons profoundly changed conventional thinking about war and peace. The magnitude of nuclear weapons' destructive power posed an entirely new order of threat in light of the specter of the instantaneous annihilation of vast numbers of people with little prospect of defense. As then-President Harry Truman put it to Congress in October 1945, "The release of atomic energy constitutes a new force too revolutionary to consider in the framework of old ideas…"

The development of nuclear technology ushered in a period of impassioned debate about the dangers posed by a nuclear arms race and proposals for ways to reduce the military incentives toward first use of nuclear weapons in a crisis. The unprecedented destructive power of nuclear weapons as well as the virtual impossibility of protecting civilian populations contributed to the view that all-out war, or total war, was suicidal. Nonetheless, in the early days of the Cold War, American and Soviet military planners relied on a strategic doctrine known aptly as "MAD"—or mutually assured destruction—which threatened the use of nuclear weapons in response to an attack as a way to deter an adversary.

During the 1950s and early 1960s, Cold War tensions contributed to a series of confrontations that repeatedly raised the specter of nuclear war. One oft-cited confrontation in 1962, known as the Cuban Missile Crisis, brought the United States to the brink of nuclear war with the Soviet Union, a prospect that was only narrowly averted at the last minute.

Meanwhile, during the Cold War, nuclear arsenals continued to grow. In this period, the United States and the Soviet Union conducted thousands of nuclear tests as they developed more sophisticated and lethal weapons systems. The two Cold War rivals ultimately amassed arsenals that totaled some 60,000 nuclear weapons. The number of declared nuclear weapon states increased from one to seven.

A fascinating paradox of nuclear weapons is that the nuclear threat hangs over all key security decisions, yet key governmental decision makers and even military planners have increasingly realized that nuclear weapons have only limited relevance and utility in most realms of international policy. Over time, a consensus has emerged among many security analysts (with some notable exceptions in the current U.S. administration) that nuclear devices are not legitimate weapons of war because of their lethality and indiscriminate nature. Furthermore, the catastrophic implications of a nuclear attack have shifted the majority opinion toward the view that there can be no winners in a nuclear war.

In a July 1996 decision regarding the legitimacy of nuclear weapons, for example, the World Court took a formal position on the issue, finding that there is no justification for the first-use of nuclear weapons. The acceptance of such a view has grown steadily over the past sixty years, starting with public revulsion and outcry in the aftermath of the bombings of Hiroshima and Nagasaki and influenced by some quarters of the military establishment as well as religious doctrine, such as the Catholic Bishops' widely distributed 1983 Pastoral Letter on War and Peace.


For a moving account of the effects of the bombing of Hiroshima, see: John Hersey, Hiroshima. (NY: Vintage Books; Reprint edition, 1989).

For an excellent introduction to WMD issues, see Joseph Cirincione, Jon Wolfsthal, Miriam Rajkumar, Deadly Arsenals: Nuclear, Biological, and Chemical Threats, Second Edition Revised and Expanded, Washington, DC: Carnegie Endowment for International Peace, 2005.

For a discussion of some of the drawbacks of the broad term "weapons of mass destruction," see: Owen R. Cote, Jr., "Weapons of Mass Confusion: A security strategy doomed to failure." Published in the April/May 2003 issue of Boston Review.


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

"Never underestimate the "infinitely great power of the infinitely small." -- French Chemist Louis Pasteur

Stated most simply, biological warfare encompasses any deliberate means to spread disease to humans, animals or plants. Biological weapons, therefore, include a daunting array of potentially deadly pathogens and toxins that can be delivered in a variety of ways. The threat ranges from the intentional poisoning of food in the form of salmonella, to the aerosol dispersal of a genetically-engineered strain of a highly infectious disease such as smallpox.

The intentional spread of infectious disease elicits a special dread and fear. Disease, with the suffering it causes and its capricious yet ineluctable spread, highlights human vulnerability. Although we recognize the omnipresent nature of germs and disease, their malicious development or use is both unnerving and repugnant. A successful BW attack could conceivably result in thousands, possibly even millions, of deaths and could cause severe disruptions to societies and economies.

The vast diversity of potential biological agents poses an enormous challenge to our security. By some estimates, there are more than 300,000 species of bacteria and at least 5,000 kinds of viruses that adversely affect humans. For centuries, societies have struggled to gain the upper hand in preventing and controlling outbreaks, administering vaccinations against polio, smallpox and other virulent diseases, teaching the importance of hygiene in preventing the spread of infectious disease. We are also familiar with the enormous toll of past epidemics, such as the many millions killed by smallpox, the black plague, or the 1918 Spanish flu pandemic. In the wake of such disease outbreaks, governments have enacted quarantines, forced inoculations, and imposed embargoes.

Today, the magnitude of the threat is growing. The rapid movement of people and goods around the world, population growth and urban centers, changing agricultural practices and increased use of antibiotics, and global warming have all complicated the governmental challenge. These changes are likely to contribute to conditions that facilitate the rapid spread of infectious disease. Recent studies suggest that a staggering 1,500 people die each hour from infectious ailments, the vast bulk of which are caused by just six groups of disease: HIV/AIDS, malaria, measles, pneumonia, tuberculosis (TB), and dysentery and other gastrointestinal disorders.

While the global pattern of human activity has increased the potential spread of disease, technological developments have also greatly increased the threat posed by biological weapons. Perhaps most significantly, with rapid developments in the field of genetic engineering, an increasing number of scientists and technicians have developed expertise in the techniques and lab equipment necessary to manufacture germ weapons. The technical expertise needed to create genetically-engineered pathogens and even entirely new classes of biological weapons has become widespread.

Currently, many tens of thousands of scientists and technicians are working in thousands of labs developing drugs and vaccines with the aim of improving crops, curing disease and developing new commercial products. Similar research and materials are used for both legitimate public health and illicit weapons applications. In just one example that attracted headlines, researchers seeking to control rodent populations by sterilizing mice unexpectedly discovered a virulent mousepox strain that could potentially be used to create an extremely lethal smallpox weapon. In this rapidly expanding and advancing field, there are no universally or even nationally enforced regulations governing the safety and security of dangerous pathogens.

All told, we face a truly transnational threat of unknown dimensions that we are currently ill-suited to address. The deadly anthrax attacks in the U.S. mail in the fall of 2001, as well as documents seized by U.S. military forces in 2002 from Afghanistan showing Al Qaeda's interest in BW, have served to heighten concern about bioterrorism. Biological weapons are relatively inexpensive and easy to produce. A primitive version of a BW can be developed in a small laboratory with readily available equipment with only limited training and expertise. Yet there remain significant technical barriers to developing and maintaining a sophisticated BW program. With this in mind, it is important to increase awareness and understanding of the dangers without unduly heightening public anxiety and fear.

Characteristics of Biological Weapons

Diseases most likely to be considered for use as biological weapons are assessed in terms of their lethality and "robustness" which normally refers to their shelf-life and effective delivery in aerosol form. To be considered a useful weapon by military planners, a biological agent must be highly infective and possess high potency. BW comes in two basic forms: liquid and dry powder. For most agents, the liquid form is easier to produce, but the dry form stores longer and disperses more widely when deployed. In contrast to the immediate effects of a chemical weapon attack, a biological weapon attack takes a while before its effects are apparent. Depending upon the type of BW agent, incubation periods range from under 24 hours to a few weeks. For this reason, biological weapons are often described as strategic or terrorist weapons, rather than as tactical weapons to be used for immediate effect on the battlefield.

The basic steps involved in making a liquid biological weapon include: obtaining a sample of the microorganisms to be used (known as the seed culture); culturing the microorganisms until enough is grown to produce a weapon; concentrating the culture to make it strong enough for a weapon; adding certain ingredients to stabilize the culture. For a dry weapon formulation, this liquid culture is dried out and then ground up into microscopic particles. For toxin weapons, the toxin must first be extracted from the source—either the liquid bacterial culture or a plant or animal—and then concentrated. It can be difficult to produce sufficiently large quantities of a particular virulent strain, so another possible avenue is to steal or obtain an existing culture from a research institute, hospital, or university lab.

While by no means exhaustive, there are about thirty different bacteria, viruses, and fungi on the NATO list of likely biological weapons threats, including: Anthrax, Brucellosis, Bubonic Plague, Cholera, Ebola, Glanders, Japanese B Encephalitis, Machupo, Q fever, Rift Valley Fever, Rocky Mountain Spotted Fever, Shigella, Smallpox, Tularemia, Typhus and Yellow Fever. Naturally-occurring toxins that can be used as weapons include: Ricin, SEB, Botulism toxin, Saxitoxin, as well as Mycotoxins. For a description of specific types of bioterrorism agents and diseases, see the U.S. Centers for Disease Control (CDC) website:

Biological weapons can be deployed in three ways: by contaminating food or water supplies, which are then ingested by the victims; by releasing infected vectors, such as mosquitoes or fleas, which then bite the victims; or by creating an aerosol cloud, which is then inhaled by the victims. With expertise and experience in developing BW agents, it is possible to produce and deploy a BW arsenal within a few months, making long-term stockpiling of large quantities of BW agents unnecessary.

History of Biological Weapons

Over the centuries, biowarfare has existed in many forms: from dropping rotting carcasses into public drinking wells to dispersing the plague by aircraft. Yet, while it is possible to find many horrendous examples of biowarfare, there are relatively few historical examples of large scale BW deployments in warfare, especially when compared to the enormous human toll caused by conventional warfare. Nonetheless, a number of nations have invested heavily in research and development of biological weapons.

One of the few countries that engaged in extensive biological warfare in the 20th century is Japan. Its research and development of agents and dissemination devices began in the early 1930s and lasted until the end of World War II in 1945. During this period, the Japanese program experimented with biological agents on human prisoners, causing at least 10,000 deaths. In addition, the Japanese dropped bombs over Manchuria and other regions of China designed to infect the population with bubonic plague between 1940 and 1941. It is unknown how many people perished as a result of these attacks; Japan has acknowledged that the BW attacks caused 20,000 deaths, while Chinese government estimates assert that there were over 200,000 casualties from these wartime attacks.
After World War II, both the United States and the former Soviet Union developed extensive offensive BW programs. Notably, for nearly two decades, the former Soviet Union and then Russia maintained perhaps the world's largest offensive biological weapons program.

At its peak in the late 1970s, Soviet bioweapons scientists conducted research on some 50 agents and weaponized roughly a dozen. Beginning in 1984, the top goal for this research was to alter the genetic structure of known pathogens such as plague and tularemia to make them resistant to Western antibiotics. By 1987, the Soviet BW program had the capacity to produce 200 kilograms of freeze-dried anthrax or plague bacteria per week. In total, about 60,000 to 70,000 people worked in various BW activities. It was not until the breakup of the Soviet Union that President Yeltsin ordered the secret programs disbanded and the full extent of Soviet offensive research was revealed. Although Russia has renounced its offensive biological weapons programs, its vast biological research and development complex still exists, contributing to ongoing fears about the dangers of proliferation.

Today, according to a recent U.S. State Department report, more than ten countries are believed to have ongoing biological warfare programs, including Russia, Israel, China, Iran, Libya, Syria and North Korea. Text available at:
Prior to 1991, Iraq pursued a vast and advanced biological warfare program. This program was uncovered and disbanded as a result of international inspections at the end of the 1990-91 Persian Gulf War. No evidence of an offensive Iraqi BW program has been found in the aftermath of the American-led invasion of Iraq in 2003.

The Biological Weapons Convention

Like the former Soviet Union, the United States pursued a large-scale offensive biological weapons program following World War II. In 1969, however, President Richard Nixon announced the U.S. decision to unilaterally renounce its offensive BW program and destroy its stockpiles. Technically, the use of BW was first outlawed in the Geneva Convention of 1925. But President Nixon's bold move to end the United State's offensive BW program led to multilateral negotiations to outlaw biological weapons entirely and, in 1972, the Biological Weapons Convention was signed.

At the time, President Nixon's military advisers concluded that biological weapons were unreliable and unpredictable. They argued that biological weapons could spread out of control and initiate epidemics in civilian populations on either side of an armed conflict; furthermore, their use might trigger a nuclear response.

As a result, the 1972 Biological Weapons Convention (BWC) bans the development, stockpiling, transfer, and use of biological weapons worldwide. The BWC was the first comprehensive disarmament treaty, having as its primary purpose the destruction of existing stockpiles of biological weapons (BW) and the prevention of their proliferation. Signatories of the Convention renounce their right to engage in military preparations for offensive biological warfare, regardless of whether they are faced with a similar threat. As such, member states renounce the right to in-kind retaliation or deterrence.

Despite its sweeping ban of an entire class of weapons, however, the BWC does not include formal measures to ensure compliance by its 144 member-states. This lack of an enforcement mechanism has undermined the effectiveness of the BWC. In the aftermath of the agreement, the United States disbanded its offensive BW program and destroyed its stockpile while the Soviet Union secretly expanded its top-secret BW programs.

As various violations came to light following the Cold War, the BWC came increasingly to be seen as a failed "gentleman's agreement" that lacked effective verification procedures. As a result, in the 1990s, prolonged negotiations were undertaken to develop possible verification measures, or what was known as an implementation protocol. Upon taking office in 2001, President George W. Bush reversed previous U.S. support of these negotiations, scuttling any prospect of an agreement on a legally binding compliance regime.

Despite the current impasse with respect to the BWC, a number of other initiatives are underway to strengthen international norms and incentives for implementing national regimes to slow and reverse proliferation and misuse of pathogens. Notably, many countries have enacted national legislation to criminalize offensive BW research.

Efforts to Improve Biosecurity

Over the past several years, the United States has dramatically increased biodefense funding and undertaken a variety of initiatives to prevent the acquisition and intentional misuse of biological agents by would-be criminals, terrorists or spies. Meanwhile, though, while most countries generally use the same four biosafety levels in classifying sensitive materials, they observe no common standards about what security measures are appropriate to each level.

While by no means alone, the United States does not have comprehensive laboratory safety laws. The current U.S. system does not even have comprehensive reporting requirements for accidental releases. Part of the problem is that labs are housed in very different types of institutions with varying degrees of oversight and accountability. These include: public universities; private universities; non-profit institutes (including non-profit research hospitals); government agencies; and the private sector, ranging from biotechnology companies to health care providers. With this in mind, there is also an urgent need for expanded training and education in biosecurity and biosafety that includes developing and implementing "best practices" to reinforce ethical norms and to uphold so-called "codes of conduct" as a tool to combat the misapplication of biology.

To be effective, these biosecurity efforts must transcend national boundaries and be interwoven with a multilayered public health approach to prevention, detection and response. This entails a greater emphasis on improving national and international disease surveillance and more effective international capabilities for responding to suspicious outbreaks.

No matter what disease strikes next, it is imperative to quickly identify and alert affected populations and appropriate authorities to dangerous outbreaks. This requires integrated strategies for combating known risks (e.g. ebola, plague), responding to the unexpected (e.g. epidemic intelligence, verification of events, assessment of humanitarian impact and coordination of rapid specialized response), and improving global, national and local preparedness.

Of crucial importance to any successful regime is the need for strengthened mechanisms to identify and report disease outbreaks as part of our effort to build national preparedness for epidemics (whether they are naturally occurring, accidental or intentional in origin). Currently, there is much promising research and development underway that offers the hope of rapid detection and identification of so-called "silent killers."

The World Health Organization (WHO), established in 1948, is responsible for coordinating the intergovernmental system of reporting disease outbreaks. Unfortunately, this system operates with very limited financial resources and depends upon voluntary reporting and contributions by member states. Quick and reliable reporting is crucial to efforts to diagnose, treat and control disease outbreaks with a minimum loss of life. Yet many regions are handicapped in this effort by glaring shortcomings in existing public health infrastructure. No matter what lies ahead, we all benefit by increasing funding and international partnerships to improve our ability to quickly identify and alert relevant public health authorities to new disease outbreaks wherever they occur around the globe.

While there is much debate over the efficacy of current biodefense programs, strengthening global efforts to detect and contain epidemics provides clear and sustainable public health benefits. The recent outbreak of Severe Acute Respiratory Syndrome (SARs) in 2003 offers a good case in point. In response to reports of severe illness and death from an unknown virus, WHO successfully managed an international partnership known as the Global Alert and Response Network (GOARN). This unprecedented international collaboration succeeded in rapidly identifying and containing the spread of SARs. The response to the outbreak of SARs offers one of the few bright spots in the realm of infectious disease that merits fuller scrutiny. In the event of the intentional release of a biological agent, WHO's global alert and response network would be a vital part of any effective international containment efforts.

Useful Links:

For various additional resources on biological weapons issues, see the Center for Nonproliferation Studies (CNS) of the Monterey Institute of International Studies.
CNS provides an overview of past and present chemical and biological weapons.
CNS also provides resources on biosecurity measures to prevent bioterrorism.

The Arms Control Association (ACA) provides an overview of BW issues, documents and analysis.

The BioWeapons Prevention Project, a civil society initiative, tracks compliance of governments and other entities with the Biological Weapons Convention and other international treaties that codify the norm against biological weapons, relevant scientific and technological developments, and measures undertaken by governments and relevant organizations to increase openness and transparency.

The Harvard-Sussex Program on Chemical and Biological Warfare is an inter-university collaboration for research, communication and training in support of informed public policy regarding chemical and biological warfare.

The Acronym Institute provides a compendium of information on the Biological Weapons Convention and Review Conferences, as well as ongoing efforts to strengthen the regime.

The Bradford Project on Strengthening the Biological and Toxin Weapons Convention.

Henry Stimson Center provides documents on BW.

For examples of educational efforts to promote awareness of biosecurity issues among biologists and interactive teaching curricula, see the Federation of American Scientists.

For a further discussion of efforts to establish a Code of Conduct to provide clear guidelines on values and professional practices that defines the expectations and directs the actions of practitioners of the Life Sciences, see:
The Interacademy Panel on International Issues (IAP).
Statement of Thomas Holohan, BWC Experts Group Meeting, U.S. State Department.

The National Security Archive compiles declassified governmental documents, including information on the Nixon Administration's decision to end its BW Program.

The Sunshine Project offers analysis supporting full transparency and improved public access to U.S. biomedical research.
In addition to various briefs, the Sunshine Project provides a search engine of research grant data from the National Institutes of Health (NIH) tracking U.S. spending on biotechnology, biodiversity, specific diseases, or funding in specific locations.

The Canadian government provides information on the BWC and its Protocol.

In the United States, a number of federal agencies are engaged in biodefense research and offer various resources. These include: the Department of Homeland Security; the National Institutes of Health and Centers for Disease Control and Prevention under the Department of Health and Human Services; the National Laboratories operated by the Department of Energy; the U.S. Army Medical Research Institute of Infectious Diseases, Dugway Proving Ground, and the Naval Medical Research Center under the Department of Defense; the U.S. Department of Agriculture; and the U.S. intelligence community.

For information on bioterrorism agents and preparedness, see the U.S. Centers for Disease Control (CDC).

The U.S. National Institute for Allergy and Infectious Diseases (part of NIH) provides a fact sheet on Anthrax.

The U.S. Food and Drug Administration provides links on bioterrorism.

The National Academies provides public safety resources on Bioterrorism for First Responders and a search engine of more than 3000 related web pages.

The Biodefense Education Organization's digital library provides biodefense news stories through the end of 2005, reference resources on biodefense and current U.S. government unclassified biodefense textbooks and manuals.

For an overview and series of recommendations on how to balance the tradeoffs between promoting beneficial research in the life sciences while minimizing the possibilities for abuse, see the National Research Council (NRC) 2003 Report, "Biotechnology Research in an Age of Terrorism."

The U.S. Department of Health and Human Resources has created the National Science Advisory Board for Biosecurity (NSABB) to provide advice to federal departments and agencies on ways to minimize the possibility that knowledge and technologies emanating from biological research will be misused.


Prepared by Laura Reed, Security Studies Program, MIT, Cambridge, MA, USA

Chemical weapons use toxic chemicals to kill, injure or incapacitate an enemy. Chemical weapons can be produced relatively easily and the equipment required is widely available. Aside from black market production, there are roughly 6,000 industrial chemical facilities worldwide where chemical weapons potentially can be produced or from which the ingredients to make chemical weapons can be acquired.

Chemical weapons have existed for thousands of years, from the earliest use of poison arrows, toxic smoke and other deadly tactics in warfare. The major development came in the early part of the twentieth century, when new manufacturing techniques and more sophisticated delivery systems changed the scope of chemical warfare by inflicting devastating casualties on a massive scale. During World War I, chemical weapons were widely used on the battlefield, causing as many as 100,000 deaths and over one million injuries. Over the course of World War II and during the Cold War, major powers developed enormous arsenals of chemical weapons that included large quantities of a more lethal variety of so-called nerve gas. The United States and Russia possess the largest and most lethal CW stockpiles. Iraq's use of chemical weapons in the Iran-Iraq war in the 1980s and the terrorist poison gas attack in the Tokyo underground railway by the cult Aum Shinrikyo in 1995 provide chilling and relatively recent examples of the indiscriminate and inhumane effects of these weapons.

Today, 175 nations have signed an international treaty prohibiting the development, stockpiling or use of chemical weapons. This agreement reflects a consensus view opposing the use of chemical weapons and commits states to destroying all existing arsenals. Although behind schedule, states are slowly undertaking to neutralize and dismantle their declared CW. Nonetheless, large stockpiles remain, containing over 71,000 metric tons of extremely toxic chemical agents. In addition, a handful of states are suspected of maintaining secret CW stockpiles and are believed to be pursuing ongoing research programs, including: North Korea, Israel, Iran, China, Syria, and Egypt.

In evaluating the risks posed by chemical weapons, two important dimensions merit scrutiny. First, many of these agents or precursors have important commercial uses and are available on the open market from a large number of production facilities. In addition, it is relatively easy to develop and store chemical weapons in secrecy. The availability of chemical ingredients and the potential for undetected clandestine manufacture and storage make the chemical industry especially vulnerable as a target of terrorism. According to the U.S. Government Accountability Office (GAO), at least 123 separate chemical facilities operating in the United States are vulnerable to attacks that could each result in one million civilian casualties. Despite this threat, however, the chemical industry has largely been spared intense public scrutiny because there has not been a major chemical accident since the chemical catastrophe in Bhopal, India in 1984. In that incident, an accidental explosion at a Union Carbide plant released chlorine gas that killed roughly 5,000 people and injured thousands more.

Types of Chemical Weapons:

Chemical weapons agents can maim and kill humans in different ways, depending on their specific toxic effects and how they enter the body. There is continuing debate over whether chemical weapons should be defined as a mass casualty weapon because the poisonous effects of chemical weapons—by inhalation, ingestion or contact with the skin—is more likely to be limited in scope than a nuclear blast or the spread of germ warfare. Nonetheless, it is now possible to develop large quantities of highly toxic chemicals that can be dispersed over great distances in a way that will kill large populations.

To date, roughly 70 varieties of toxic chemicals have been used or stockpiled for use in warfare. These chemical agents fall into four major classes or types:

Choking or Pulmonary agents, such as phosgene, or chlorine gas, attack lung tissue and cause respiratory distress and asphyxiation.

Blister agents, or vesicants, including mustard gas and Lewisite, cause blisters on the skin and in the respiratory tract that can result in death, or long-term debilitating injuries, including respiratory damage and blindness.

Blood agents, such as cyanide or cyanogen chloride, can kill humans by interfering with the body's oxygen supply.

Nerve agents, such as Tabun, Sarin, Soman, and VX are lethal in the most minute quantities, causing rapid death by incapacitating the body's central nervous system.

For a comprehensive listing of the characteristics of known chemical agents, see the Centers for Disease Control (CDC) website which provides information on characteristics and related resources, including emergency preparedness, surveillance, and response:

Thirteen countries are believed to possess chemical weapons and six of these states have pledged to eliminate declared stockpiles under a global chemical weapons ban treaty, known as the Chemical Weapons Convention. For a comprehensive overview and history of the use of chemical weapons in warfare and the regulation of dangerous chemical agents, see:

History of Chemical Weapons

In contrast to other WMD, it is notable how little the technology of chemical warfare has changed over the past half-century. Perhaps the most significant developments are the increasingly sophisticated manufacturing facilities available and improved techniques for CW dispersal (generally using explosives and aerosols). While the most common military delivery systems include artillery shells, bombs, spray tanks, missiles, rockets, grenades, and mines, other methods of distribution, such as crop-dusting aircraft, pesticide foggers, and aerosol sprays have also been developed.

From a technological and military perspective, the most significant advances in chemical warfare occurred during the two World Wars. Germany was the first to use chemical weapons on the battlefield during World War I and, during that conflict, phosgene and sulphur mustard (a blistering agent) caused some 100,000 deaths and over one million injuries. At the time, some senior military officials argued that chemical weapons were a more humane form of killing on the battlefield because of the weapons' relatively fast and deadly effects. During World War II, Nazi Germany developed and manufactured large quantities of newly discovered nerve agents, but refrained from using them against Allied forces. The Nazis used the insecticide Zyklon B to kill large numbers of Jews and other victims in concentration camps during the Holocaust. Widespread public horror over the use of chemical weaponry as well as fears of retaliation in kind have, at least some degree, curbed the use of chemical weapons.

The general taboo against the use of chemical weapons in warfare holds to this day, despite the existence of enormous aging stockpiles. There are a few notable exceptions that merit attention. Although defined as an herbicide rather than a chemical weapon, the United States used a defoliant called Agent Orange during the Vietnam War which contained the cancer-causing agent, dioxin. In early 1984, a United Nations investigation team found that Iraq had used chemical weapons in the Iran-Iraq war, and that at least some of the precursor chemicals and materials for its CW program had been purchased through legitimate trade channels. In 1987, Libya used chemical weapons against Chadian troops. In 1988, Iraq carried out chemical attacks in northern Iraq that killed roughly one hundred thousand Kurds; since the attacks, thousands more Kurds have developed skin cancers, degenerative nerve conditions, and birth defects.

Several criminal and terrorist uses of chemical weapons have occurred over the past several decades, but perhaps the most notable was, as mentioned above, the development and use of chemical weapons by the Japanese cult Aum Shinrikyo. In 1995, members of this cult used the nerve agent Sarin in an attack on the Tokyo subway. Twelve people died and 5,000 were injured.

The Chemical Weapons Convention

The Chemical Weapons Convention, or CWC, prohibits the development, production, stockpiling, acquisition, or transfer of chemical weapons. A remarkable accomplishment, the CWC is the first disarmament agreement negotiated within a multilateral framework that provides for the elimination of an entire category of weapons of mass destruction under universally applied international control. Notably, the treaty not only outlaws the use of chemical weapons, but commits nations to eliminating existing stockpiles of these weapons. This work is carried on under the auspices of the Organization for the Prohibition of Chemical Weapons (OPCW) which oversees verification and inspection efforts.

The CWC entered into force in April 1997 and now has 175 signatories. The CWC is unique because it provides for the international verification of the destruction of these weapons and was negotiated with the active participation of the global chemical industry, thus ensuring industry's ongoing cooperation with the CWC's industrial verification regime. The Convention mandates the inspection of industrial facilities to ensure that toxic chemicals are used exclusively for purposes not prohibited by the Convention.

Nonetheless, many believe that the threat posed by chemical weapons has not diminished significantly for three main reasons: a handful of nations suspected of possessing chemical weapons have refused to sign on to the treaty (notably, North Korea, Israel, Syria, Taiwan and Egypt); the vast majority of chemical weapons have not yet been destroyed; and the widespread availability of the precursors and technologies underlying chemical weapons. In response to ongoing fears about the spread of chemical weapons, a group of countries (known as the Australia Group) has established export controls to regulate chemical precursors and coordinate policies regarding current industry practices.

Over the past decade, the United States and Russia have undertaken to destroy their vast, aging stockpiles of chemical weapons. However, the destruction of chemical weapons requires significant financial resources and presents enormous operational and technical complexities. The variety of weapons to be destroyed, daunting technical challenges, program management issues, and community concerns over public health and environmental risks have contributed to delayed progress. Over 65,000 tons of deadly chemical weapons await destruction in Russia and the United States. In the United States, the demilitarization program is now underway at eight facilities, but much work remains. As of the end of 2005, the United States had destroyed just 36 percent of its original stockpile while Russia had destroyed only about 3 percent of its stockpile. In addition, thousands more chemical weapons sit in abandoned or uncharted dumps that date back to the Second World War.

Overall, nations with chemical weapons stockpiles have lagged behind in destroying them as scheduled by the Chemical Weapons Convention: of the 70,000 metric tons of declared weapons agents, the Organization for the Prohibition of Chemical Weapons (OPCW) has verified the destruction of only 12,000 tons. If the current pace persists, the Convention's goal to complete the destruction of chemical weapons stockpiles will not be met by the extended deadline of 2012.

While much remains to be accomplished, the Chemical Weapons Treaty marks a major milestone in terms of progress toward demilitarization. At the first review conference on implementing the CWT, leaders assessed it as follows: "The Chemical Weapons Convention performs a vital confidence-building role in international society. Reinforced by effective national legislation, the CWC enables its States parties to satisfy themselves that others are not seeking to acquire such weapons. The Convention thus serves a practical goal of enhancing security, a moral goal of eliminating one of the world's most cruel and inhumane weapons, and a political goal of establishing a common forum for reaffirming and strengthening the global taboo on such weapons."

Useful Links:

The Arms Control Association (ACA), a nonprofit based in Washington, DC, provides documents, news analyses, and fact sheets on chemical weapons issues.

The Center for Nonproliferation Studies (CNS) of the Monterey Institute of International Studies provides educational information, news updates (called ChemBio-WMD Terrorism News) and additional links.

The Nuclear Threat Initiative (NTI) maintains an extensive website with a variety of resources, including updates on the progress of chemical weapons assistance and state programs.

The Center for Defense Information (CDI) offers information on the chemical weapons convention and technical issues.

For a chronology of the Chemical Weapons Convention, see the Federation of American Scientists (FAS).

The National Library of Medicine, sponsored by NIH, gives information and links on classes of chemical weapons, environmental and health effects, and emergency response.

The Organization for the Prohibition of Chemical Weapons (OPCW) provides a variety of resources, including documents and updates on adherence and verification of the Treaty.

The U.S. Defense Threat Reduction Program provides information on the military features of chemical weapon agents and the status of U.S. efforts to dismantle its stockpile.

For information on the eight U.S. Army installations currently storing chemical agents and progress of the U.S. chemical demilitarization program, see the Chemical Materials Agency (CMA).

The Legacy Program of Global Green, an international environmental group working for the safe and timely cleanup of existing CW stockpiles, maintains updates on programs to demilitarize stockpiles in the Former Soviet Union through the U.S. Cooperative Threat Reduction Program.





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