"Chemical" and "biological" are difficult terms to define. U.S. Army Field Manual 3–100, NBC Defense, Chemical Warfare, Smoke, and Flame Operations (1991) defines a biological agent as "a micro-organism that causes disease in man, plants, or animals, or deterioration of materiel." A chemical agent is defined as a "chemical substance intended for use in military operations to kill, seriously injure, or incapacitate humans through its physiological effects." This definition excludes riot control agents, herbicides, smoke, and flame and is a matter of diplomatic debate. Tear gas agents present a special case, as these are now included under the rubric of chemical agents but have been used by military forces in cases that resemble nonmilitary crowd control actions.
The history of chemical warfare goes back for millennia. More than 2,000 years ago, the Chinese used smoke pots and the Japanese used pepper spray as lachrymatory agents. During the sieges of Platea and Belium, the Spartans used burning pitch and sulfur in attempts to overcome the cities' inhabitants. Flaming chemicals such as Greek fire were employed in ancient times. More recently, the British used burning sulfur against the Russians in the 1855 siege of Sebastapol. Similar agents were used by both sides in the U.S. Civil War before the 1907 Hague Conference, over Admiral Alfred Thayer Mahan's objections, declared chemical weapons inhumane.
Biological weapons have also been used for centuries. Ancient warriors poisoned wells with decomposing bodies of animals, and there is a (possibly apocryphal) story that Mongol soldiers catapulted infected corpses into Genoese trading settlements on the Black Sea and precipitated the first wave of European bubonic plague. Lord Jeffrey Amherst and the British Army have been accused (again, possibly apocryphally) of giving blankets infected with smallpox to North American Indians.
The French were actually the first to use chemical weapons during World War I, having tried grenades filled with the irritant xylyl bromide in August 1914. In October 1914 at Neuve Chapelle and again in January 1915 at Bolimov on the Eastern Front, the Germans tried artillery shells filled with chemical irritants. The first large-scale use of chemical weapons was at the Second Battle of Ypres, when Germany released a cloud of chlorine gas that drifted over British, Canadian, French, and Algerian forces. By September 1915, the British had begun using chlorine as well, although the gas was subject to the vagaries of shifting winds and was generally of limited effectiveness. This disadvantage led to a return to delivery by artillery shells.
Chlorine was soon replaced by the more potent irritants phosgene and mustard gas. Phosgene (coded CX) caused less immediate coughing, so more was inhaled; however, it caused more delayed pulmonary damage than chlorine. Diphosgene (coded DG) and chloropicrin (coded PS) were later pulmonary irritants. Mustard gas (both nitrogen and sulfur variants) was first used against the Russians at Riga in 1917 and was delivered in artillery shells. Unlike the earlier agents, it blistered the skin as well as damaged the lungs and was more difficult to defend against since gas masks alone were insufficient protection. The final blistering agent developed was Lewisite (coded L), a liquid arsenical agent for which Dimercaprol (British Anti-Lewisite or BAL) is an antidote.
Once combatants developed protection mechanisms, gas warfare became relatively ineffective. After May 1915, only about 9 percent of British casualties were from gas, and only about 3 percent of those were fatal, although many victims had permanent disabilities.
There was a generally negative reaction to the use of chemical weapons, and they were banned by international agreement in the Geneva Protocol on Gas Warfare (signed in 1925) that went into effect in 1928. Nonetheless, America, Britain, Japan, and the Soviet Union continued to experiment with chemical and biological weapons. The greatest advances were made by Germany with the development of hydrogen cyanide (which interferes with cellular oxygen metabolism and one form of which, under the name Zyklon B, was used for genocide) and the nerve gases tabun (coded GA by the U.S. military), sarin (GB), and soman (GD). (Since GC was military medical shorthand for gonorrhea, those letters were not used as a gas designation.) The nerve gases act by inhibiting breakdown of the neurotransmitter acetylcholine and cause runny nose, wheezing, drooling, involuntary defecation and urination, and, ultimately, convulsions, coma, and death. Following World War II, the Soviets developed a thickened version of Soman that could be deployed from spray tanks and made it the major part of their chemical arsenal. Sarin was used by Japanese terrorists in the Tokyo subway in the 1990s.
Although Italy employed mustard gas with devastating effect in its conquest of Ethiopia in 1935–1936, the threat of retaliation prevented the use of poison gases against combatants in World War II, with the exception of infrequent use by the Japanese in China.
In 1936 the Japanese Army established its infamous Unit 731 in Manchuria to test and refine chemical and biological weapons. After the war the United States granted immunity from prosecution to the members of this unit in exchange for the information on the experiments, even though a number were conducted on humans. Washington considered this work invaluable in its own biological warfare program, although the Soviet government prosecuted twelve members of the unit in December 1949.
VX gas, a neurotoxin, was developed at the Porton Down Chemical Research Centre in Wiltshire, England, in 1952. The British subsequently traded the technology for VX production with the United States in return for data on production of thermonuclear weapons. Unlike sarin and tabun, VX is a liquid that adheres to surfaces, is difficult to remove, and persists for long periods. In liquid form, it is absorbed through the skin and can cause death in one to two hours. In its gaseous form, it causes death almost instantly. It is usually fatal in doses of ten milligrams, although the anticholinergic drug Atropine is an effective antidote and is regularly supplied to troops at risk of chemical attack. Atropine can be applied subcutaneously to counteract liquid VX but must be given directly into the heart to counteract the gaseous form.
A final agent bridges the gap between chemical and biological warfare. Ricin is a protein toxin derived from castor beans that causes respiratory failure thirty-six to seventy-two hours after being inhaled or clotting failure, shock, and multiple organ failure after being ingested or injected. Bulgarian exile Georgi Markov was said to have been assassinated by the Soviet KGB in London using a sharpened umbrella tip contaminated with ricin.
The fact that the Soviets considered chemicals viable weapons became evident during the Yom Kippur War of 1973, when the Israelis captured Soviet-manufactured Egyptian tanks that utilized overpressure systems to protect against gaseous agents by maintaining a constant pressure differential between the inside of the vehicle and the outside environment. This information reversed efforts within the U.S. Army to abolish the Chemical Corps, the agency charged with conducting chemical defensive and offensive operations. The Chemical Corps was then directed to enhance defensive procedures and develop new chemical binary weapons. These latter were designed to be safer to deploy for the troops using them, as the lethal gases were not created until the projectiles were actually en route to target, when two chemicals combined within the projectile being fired.
Both sides worked on biological weapons throughout much of the Cold War, the United States at Fort Detrick, Maryland, and the Soviet Union on Vozrozhdeniye Island in the Aral Sea. Fort Detrick was decommissioned in 1970 when President Richard Nixon made a unilateral policy decision to abandon biological warfare. The Soviet facility remained open until 1992, housing a small city of 1,500 people and sophisticated animal testing facilities, although, according to Gennadi Lepyoshkin, who directed the facility until its closure, the majority of research was defensive and was concentrated on protection against bacterial agents such as plague, botulism, and anthrax.
Although smallpox was eradicated worldwide in 1977, both the United States and the Soviet Union retained samples of the organism, and there has been persistent suspicion that one or both might have altered the virus to make it a usable weapon. In 2001, anthrax-contaminated letters were sent to members of Congress in Washington, to television news stations in New York, and to a Florida newspaper, although the source of the agent and the reasons for its use remain unknown. Although neither the Soviet Union nor the United States overtly used chemical agents against humans during the Cold War, toxic chemicals have been widely used against plants. Between 1962 and 1971, the United States sprayed about 11 million gallons of Agent Orange (a mixture of two phenoxy herbicides) over 6 million acres of Vietnamese forest. There have been persistent claims that either Agent Orange or the dioxin with which it was contaminated caused birth defects, delayed neurological damage, and cancer, although these claims have been difficult to prove definitively.
Since the close of the Cold War, there have been scattered rumored and verified uses of chemical weapons against enemy combatants or civilians including use by Egypt against Yemen, by Iraq against Iran, and by Iraq against its own Kurdish population. The United States maintains an active educational and logistic chemical defense program at Fort Leonard Wood, Missouri. Jack McCallum and Daniel E. Spector
Bailey, Kathleen C. Doomsday Weapons in the Hands of Many. Urbana: University of Illinois Press, 1991.; Gilchrist, H. L., ed. Warfare Gases: Their History, Description, Medical Aspects, and After Effects. Washington DC: War Department, 1925.; Harris, Robert, and Jeremy Paxman. A Higher Form of Killing: The Secret Story of Chemical and Biological Warfare. New York: Hill and Wang, 1982.; Heller, Charles E. Leavenworth Papers: Chemical Warfare in World War I; The American Experience, 1917–1918. Washington, DC: U.S. Government Printing Office, 1943.; Williams, Peter, and David Wallace. Unit 731: Japan's Secret Biological Warfare in World War II. New York: Free Press, 1989.
Jack McCallum and Daniel E. Spector