The continued search in 2003 for Weapons of mass destruction (WMD) in Iraq heightened curiosity concerning the definition of WMD. The term has been in use since at least 1937, when newspapers described German bomber aircraft as “weapons of mass destruction” because they were being used to raze Republican-held cities during the Spanish Civil War. During the Cold War, WMD was narrowly defined to include only nuclear weapons because their use threatened the entire planet. By the end of the 1990–91 Gulf War, WMD had been used in United Nations Security Council Resolution 687—which imposed on Iraq strict rules for disarmament—to describe nuclear, biological, and chemical weapons. Since that time others have tried to alter the definition to include any weapon that disperses radioactivity or causes mass panic.

Nuclear Weapons. Nuclear weapons are thus far the most devastating weapon of mass destruction. They inflict their damage by a combination of intense blast, heat, electromagnetic energy, and radioactivity. Within a few minutes the single rudimentary bomb dropped on Hiroshima in August 1945 killed tens of thousands of people and destroyed all the buildings inside a 1.6-km (1-mi) radius of “ground zero” (i.e., the point of impact). Nuclear weapons get their explosive power from a sustained nuclear chain reaction involving fission (the splitting of atoms) or fusion (the combining of lighter atoms to form new heavier ones). Creating such a chain reaction requires either highly enriched uranium (HEU) or plutonium. Plutonium occurs very rarely in nature and must be made inside a nuclear reactor. Uranium ore contains about 0.7% U-235 (the isotope needed to sustain an explosive chain reaction) and must be refined until the U-235 content is at least 90%. About 50 kg (110 lb) of HEU or 10 kg (22 lb) of plutonium are needed to build a crude nuclear bomb. To acquire even these small amounts, one requires a sophisticated enrichment plant or a nuclear reactor and reprocessing facility to extract plutonium; alternatively, one could acquire HEU or plutonium from someone with such facilities. Get exclusive access to content from our 1768 First Edition with your subscription. Subscribe today The cornerstones of the effort to control the spread of nuclear weapons materials and technologies are the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which has nearly 200 member states and came into force in 1970, and the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which still requires signature by India, Pakistan, and North Korea. Before it can come into force, nine other countries, including the United States, must ratify the CTBT. The International Atomic Energy Agency (IAEA), established under the auspices of the United Nations in 1957, helps ensure that states live up to their NPT obligations.

Chemical Weapons. During World War I both the German and the Allied armies used chemical weapons (CW) as a means of breaking the deadlock of trench warfare. By war’s end in 1918, approximately one million soldiers and civilians had been injured by this type of weapon, and nearly 100,000 had died. More recently, CW were used during the 1980–88 war between Iran and Iraq, most often by the Iraqis, who were trying to overcome the numerical superiority of the Iranian army. CW are divided into four categories: • Choking agents, such as chlorine and phosgene gas, are the oldest and the easiest to manufacture. These have a corrosive effect on the lining of the lungs, causing fluid buildup, but they can easily be defended against by wearing a gas mask

• Blood agents, such as hydrogen cyanide and cyanogen chloride gas, work by preventing red blood cells from absorbing oxygen and transmitting it throughout the body.

• Blister agents attack any exposed area of the body, and to defend against them personnel must wear cumbersome protective clothing as well as a gas mask. Mustard gas (sulfur mustard) and lewisite are examples of blister agents.

• Nerve agents were developed in the 1930s to be more lethal and faster acting than previous types of CW. They are absorbed through the skin or lungs and within seconds will disrupt the transmission of nerve signals to and from the brain. These agents include sarin, tabun, and VX. Controlling the proliferation of CW is difficult because many of the chemicals involved in their production also have nonmilitary uses. For example, thiodiglycol is used to make mustard gas but is also an ingredient in ink for felt-tip pens. The Chemical Weapons Convention is the first international treaty intended to eliminate an entire category of WMD. The treaty came into force in 1997, and member states have 10 years to eliminate their CW stockpiles and any related infrastructure. The treaty established the Organisation for the Prohibition of Chemical Weapons to monitor and ensure its provisions. This is done through a series of rigorous scheduled and short-notice inspections of known or suspected CW facilities and through the investigation of incidents of alleged use.

Biological Weapons. Biological weapons (BW) encompass pathogens (bacteria, viruses, and fungi) that cause diseases and toxins that are derived from organisms such as plants, snakes, and insects. Anthrax and smallpox are examples of pathogens. An example of a toxin is ricin, which is derived from the seed of the castor bean. Crude forms of biological warfare have been used since ancient times, when the decaying corpses of animals and humans were placed near enemy food and water supplies with the intention of spreading disease. In the18th century the British distributed blankets contaminated with smallpox to decimate the Indian tribes with which they were warring. During World War II the Japanese used various BW agents against the Chinese. Britain, the Soviet Union, and the U.S. all had significant BW programs during the Cold War. BW pose a special problem for arms controllers, because most of the equipment and materials used in their production also have peaceful commercial uses. There is very little observable difference between a BW factory and a medical research facility or pharmaceutical plant. The Biological and Toxin Weapons Convention bans all BW and their production facilities. It has over 140 member states and has been in force since 1975. Its members, however, have been unable to reach an agreement on how to verify the treaty. In 2001 the United States pulled out of talks to reach a verification protocol, in part over concerns that the proposed inspections would be so intrusive as to threaten the security of proprietary information owned by pharmaceutical companies.