From Wikipedia, the free encyclopedia

This article forms part of the series Chemical warfare
(A subset of Weapons of mass destruction)
Lethal agents
Blood agents
Cyanogen chloride (CK)
Hydrogen cyanide (AC)
Blister agents
Lewisite (L)
Sulfur mustard gas (HD, H, HT, HL, HQ)
Nitrogen mustard gas (HN1, HN2, HN3)
Nerve agents
G-Agents
Tabun (GA), Sarin (GB) Soman (GD), Cyclosarin (GF)
GV
V-Agents
VE, VG, VM, VX
Novichok agents
Pulmonary agents
Chlorine
Chloropicrin (PS)
Phosgene (CG)
Diphosgene (DP)
"Non-lethal" agents
Incapacitating agents
Agent 15 (BZ)
Kolokol-1
Riot control agents
Pepper spray (OC)
CS gas
CN gas (mace)
CR gas This box: view • talk • edit

Chemical warfare involves using the toxic properties of chemical substances to kill, injure or incapacitate an enemy.

Chemical warfare is different from the use of conventional weapons or nuclear weapons because the destructive effects of chemical weapons are not primarily due to any explosive force. The offensive use of living organisms (such as anthrax) is considered to be biological warfare rather than chemical warfare; the use of nonliving toxic products produced by living organisms (e.g., toxins such as botulinum toxin, ricin, or saxitoxin) is considered chemical warfare under the provisions of the Chemical Weapons Convention. Under this Convention, any toxic chemical, regardless of its origin, is considered as a chemical weapon unless it is used for purposes that are not prohibited (an important legal definition, known as the General Purpose Criterion).

About 70 different chemicals have been used or stockpiled as Chemical Weapons (CW) agents during the 20th century. Chemical weapons are classified as weapons of mass destruction by the United Nations, and their production and stockpiling was outlawed by the Chemical Weapons Convention of 1993. Under the Convention, chemicals that are toxic enough to be used as chemical weapons, or may be used to manufacture such chemicals, are divided into three groups according to their purpose and treatment:

• Schedule 1 – Have few, if any, legitimate uses. These may only be produced or used for research, medical, pharmaceutical or protective purposes (i.e. testing of chemical weapons sensors and protective clothing). Examples include nerve agents, ricin, lewisite and mustard gas. Any production over 100 g must be notified to the OPCW and a country can have a stockpile of no more than one tonne of these chemicals.
• Schedule 2 – Have no large-scale industrial uses, but may have legitimate small-scale uses. Examples include dimethyl methylphosphonate, a precursor to sarin but which is also used as a flame retardant and Thiodiglycol which is a precursor chemical used in the manufacture of mustard gas but is also widely used as a solvent in inks.
• Schedule 3 – Have legitimate large-scale industrial uses. Examples include phosgene and chloropicrin. Both have been used as chemical weapons but phosgene is an important precursor in the manufacture of plastics and chloropicrin is used as a fumigant. Any plant producing more than 30 tonnes per year must be notified to, and can be inspected by, the OPCW.

A Swedish Army soldier wearing a chemical agent protective suit (C-vätskeskydd) and his protection mask (skyddsmask 90).

Although crude chemical warfare has been employed in many parts of the world for thousands of years, "modern" chemical warfare began during World War I (see main article - Poison gas in World War I). Initially, only well-known commercially available chemicals and their variants were used. These included chlorine and phosgene gas. The methods of dispersing these agents during battle were relatively unrefined and inefficient.

Germany, the first side to employ chemical warfare on the battlefield,^[1] simply opened canisters of chlorine upwind of the opposing side and let the prevailing winds do the dissemination. Soon after, the French modified artillery munitions to contain phosgene – a much more effective method that became the principal means of delivery.

Since the development of modern chemical warfare in World War I, nations have pursued research and development on chemical weapons that falls into four major categories: new and more deadly agents; more efficient methods of delivering agents to the target (dissemination); more reliable means of defense against chemical weapons; and more sensitive and accurate means of detecting chemical agents.

See also: List of chemical warfare agents

A chemical used in warfare is called a chemical warfare agent (CWA). About 70 different chemicals have been used or stockpiled as chemical warfare agents during the 20th century and the 21st century. These agents may be in liquid, gas or solid form. Liquid agents are generally designed to evaporate quickly; such liquids are said to be volatile or have a high vapor pressure. Many chemical agents are made volatile so they can be dispersed over a large region quickly.

The earliest target of chemical warfare agent research was not toxicity, but development of agents that can affect a target through the skin and clothing, rendering protective gas masks useless. In July 1917, the Germans first employed mustard gas, the first agent that circumvented gas masks. Mustard gas easily penetrates leather and fabric to inflict painful burns on the skin.

Chemical warfare agents are divided into lethal and incapacitating categories. A substance is classified as incapacitating if less than 1/100 of the lethal dose causes incapacitation, e.g., through nausea or visual problems. The distinction between lethal and incapacitating substances is not fixed, but relies on a statistical average called the LD₅₀.

One way to classify chemical warfare agents is according to their persistency, a measure of the length of time that a chemical agent remains effective after dissemination. Chemical agents are classified as persistent or nonpersistent.

Agents classified as nonpersistent lose effectiveness after only a few minutes or hours. Purely gaseous agents such as chlorine are nonpersistent, as are highly volatile agents such as sarin and most other nerve agents. Tactically, nonpersistent agents are very useful against targets that are to be taken over and controlled very quickly. Generally speaking, nonpersistent agents present only an inhalation hazard.

By contrast, persistent agents tend to remain in the environment for as long as a week, complicating decontamination. Defense against persistent agents requires shielding for extended periods of time. Non-volatile liquid agents, such as blister agents and the oily VX nerve agent, do not easily evaporate into a gas, and therefore present primarily a contact hazard.

Chemical warfare agents are organized into several categories according to the manner in which they affect the human body. The names and number of categories varies slightly from source to source, but in general, types of chemical warfare agents are as follows:

There are other chemicals used militarily that are not scheduled by the Chemical Weapons Convention, and thus are not controlled under the CWC treaties. These include:

• Defoliants that destroy vegetation, but are not immediately toxic to human beings. Some batches of Agent Orange, for instance, used by the United States in Vietnam, contained dioxins as manufacturing impurities. Dioxins, rather than Agent Orange itself, have long-term cancer effects and for causing genetic damage leading to serious birth deformities.
• Incendiary or explosive chemicals (such as napalm, extensively used by the United States in Vietnam, or dynamite) because their destructive effects are primarily due to fire or explosive force, and not direct chemical action.
• Viruses, bacteria, or other organisms. Their use is classified as biological warfare. Toxins produced by living organisms are considered chemical weapons, although the boundary is blurry. Toxins are covered by the Biological Weapons Convention.

For more details on this topic, see chemical weapon designation.

Most chemical weapons are assigned a one- to three-letter "NATO weapon designation" in addition to, or in place of, a common name. Binary munitions, in which precursors for chemical warfare agents are automatically mixed in shell to produce the agent just prior to its use, are indicated by a "-2" following the agent's designation (for example, GB-2 and VX-2).

Some examples are given below:

The most important factor in the effectiveness of chemical weapons is the efficiency of its delivery, or dissemination, to a target. The most common techniques include munitions (such as bombs, projectiles, warheads) that allow dissemination at a distance and spray tanks which disseminate from low-flying aircraft. Developments in the techniques of filling and storage of munitions have also been important.

Although there have been many advances in chemical weapon delivery since World War I, it is still difficult to achieve effective dispersion. The dissemination is highly dependent on atmospheric conditions because many chemical agents act in gaseous form. Thus, weather observations and forecasting are essential to optimize weapon delivery and reduce the risk of injuring friendly forces.

Dispersion of chlorine in World War I

Dispersion is the simplest technique of delivering an agent to its target. It consists of placing the chemical agent upon or adjacent to a target immediately before dissemination, so that the material is most efficiently used.

World War I saw the earliest implementation of this technique, when German forces at Ypres simply opened cylinders of chlorine and allowed the wind to carry the gas across enemy lines. While simple, this technique had numerous disadvantages. Moving large numbers of heavy gas cylinders to the front-line positions from where the gas would be released was a lengthy and difficult logistical task. Stockpiles of cylinders had to be stored at the front line, posing a great risk if hit by artillery shells. Gas delivery depended greatly on wind speed and direction. If the wind was fickle, as at Loos, the gas could blow back, causing friendly casualties. Gas clouds gave plenty of warning, allowing the enemy time to protect themselves, though many soldiers found the sight of a creeping gas cloud unnerving. Also gas clouds had limited penetration, capable only of affecting the front-line trenches before dissipating. Although it produced limited results in World War I, this technique shows how simple chemical weapon dissemination can be.

Shortly after this "open canister" dissemination, French forces developed a technique for delivery of phosgene in a non-explosive artillery shell. This technique overcame many of the risks of dealing with gas in cylinders. First, gas shells were independent of the wind and increased the effective range of gas, making any target within reach of guns vulnerable. Second, gas shells could be delivered without warning, especially the clear, nearly odorless phosgene — there are numerous accounts of gas shells, landing with a "plop" rather than exploding, being initially dismissed as dud high explosive or shrapnel shells, giving the gas time to work before the soldiers were alerted and took precautions.

The major drawback of artillery delivery was the difficulty of achieving a killing concentration. Each shell had a small gas payload and an area would have to be subjected to saturation bombardment to produce a cloud to match cylinder delivery. A British solution to the problem was the Livens Projector. This was effectively a large-bore mortar, dug into the ground that used the gas cylinders themselves as projectiles - firing a 14 kg cylinder up to 1500 m. This combined the gas volume of cylinders with the range of artillery.

Over the years, there were some refinements in this technique. In the 1950s and early 1960s, chemical artillery rockets contained a multitude of submunitions, so that a large number of small clouds of the chemical agent would form directly on the target.

An American-made MC-1 gas bomb

Thermal dissemination is the use of explosives or pyrotechnics to deliver chemical agents. This technique, developed in the 1920s, was a major improvement over earlier dispersal techniques, in that it allowed significant quantities of an agent to be disseminated over a considerable distance. Thermal dissemination remains the principal method of disseminating chemical agents today.

Most thermal dissemination devices consist of a bomb or projectile shell that contains a chemical agent and a central "burster" charge; when the burster detonates, the agent is expelled laterally.

Thermal dissemination devices, though common, are not particularly efficient. First, a percentage of the agent is lost by incineration in the initial blast and by being forced onto the ground. Second, the sizes of the particles vary greatly because explosive dissemination produces a mixture of liquid droplets of variable and difficult to control sizes.

The efficacy of thermal detonation is greatly limited by the flammability of some agents. For flammable aerosols, the cloud is sometimes totally or partially ignited by the disseminating explosion in a phenomenon called flashing. Explosively disseminated VX will ignite roughly one third of the time. Despite a great deal of study, flashing is still not fully understood, and a solution to the problem would be a major technological advance.

Despite the limitations of central bursters, most nations use this method in the early stages of chemical weapon development, in part because standard munitions can be adapted to carry the agents.

Soviet chemical weapons canisters from a stockpile in Albania

Aerodynamic dissemination is the non-explosive delivery of a chemical agent from an aircraft, allowing aerodynamic stress to disseminate the agent. This technique is the most recent major development in chemical agent dissemination, originating in the mid-1960s.

This technique eliminates many of the limitations of thermal dissemination by eliminating the flashing effect and theoretically allowing precise control of particle size. In actuality, the altitude of dissemination, wind direction and velocity, and the direction and velocity of the aircraft greatly influence particle size. There are other drawbacks as well; ideal deployment requires precise knowledge of aerodynamics and fluid dynamics, and because the agent must usually be dispersed within the boundary layer (less than 200–300 ft above the ground), it puts pilots at risk.

Significant research is still being applied toward this technique. For example, by modifying the properties of the liquid, its breakup when subjected to aerodynamic stress can be controlled and an idealized particle distribution achieved, even at supersonic speed. Additionally, advances in fluid dynamics, computer modeling, and weather forecasting allow an ideal direction, speed, and altitude to be calculated, such that warfare agent of a predetermined particle size can predictably and reliably hit a target.

Ideal protection begins with nonproliferation treaties such as the Chemical Weapons Convention, and detecting, very early, the signatures of someone building a chemical weapons capability. These include a wide range of intelligence disciplines, such as economic analysis of exports of dual-use chemicals and equipment, human intelligence ([HUMINT]) such as diplomatic, refugee, and agent reports; photography from satellites, aircraft and drones (IMINT); examination of captured military and terrorist equipment (TECHINT); communications intercepts (COMINT); and detection of chemical manufacturing and chemical agents themselves ( MASINT).

If all the preventive measures fail and a clear and present danger, then there are needs for detection of chemical attacks^[2] and collective protection^{[3] [4]} and collective protection^[5], and decontamination. Since industrial accidents can cause dangerous chemical releases (e.g., the Bhopal disaster), these activities are things that civilian, as well as military, organizations must be prepared to carry out. In civilian situations in developed countries, these are duties of HAZMAT organizations, which most commonly are part of fire departments.

Detection has been referred to above, as a technical MASINT discipline; specific military procedures, which are usually the model for civilian procedures, depend on the equipment, expertise, and personnel available. When chemical agents are detected, an alarm needs to sound, with specific warnings over emergency broadcasts and the like. There may be a warning to expect an attack. If, for example, the captain of a US Navy ship believes there is a serious threat of chemical, biological, or radiological attack, the crew may be ordered to set Circle William, which means closing all openings to outside air, running breathing air through filters, and possibly starting a system that continually washes down the exterior surfaces. Civilian authorities dealing with an attack or a toxic chemical accident will invoke the Incident Command System, or local equivalent, to coordinate defensive measures^[6].

Individual protection starts with a gas mask and, depending on the nature of the threat, through various levels of protective clothing up to a complete chemical-resistant suit with a self-contained air supply. The US military defines various levels of MOPP (mission-oriented protective posture) from mask to full chemical resistant suits; Hazmat suits are the civilian equivalent, but go farther to include a fully independent air supply, rather than the filters of a gas mask.

Collective protection allows continued functioning of groups of people in buildings or shelters, the latter which may be fixed, mobile, or improvised. With ordinary buildings, this may be as basic as plastic sheeting and tape, although if the protection needs to be continued for any appreciable length of time, there will need to be an air supply, typically a scaled-up version of a gas mask^{[7] [8]}.

Decontamination varies with the particular chemical agent used. Some nonpersistent agents, such as most pulmonary agents such as chlorine and phosgene, blood gases, and nonpersistent nerve gases (e.g., GB) will dissipate from open areas, although powerful exhaust fans may be needed to clear out building where they have accumulated. In some cases, it might be necessary to neutralize them chemically, as with ammonia as a neutralizer for hydrogen cyanide or chlorine. Riot control agents such as CS will dissipate in an open area, but things contaminated with CS powder need to be aired out, washed by people wearing protective gear, or safely discarded.

Mass decontamination is a less common requirement for people than equipment, since people may be immediately affected and treatment is the action required. It is a requirement when people have been contaminated with persistent agents. Treatment and decontamination may need to be simultaneous, with the medical personnel protecting themselves so they can function^[9]. There may need to be immediate intervention to prevent death, such as injection of atropine for nerve agents. Decontamination is especially important for people contaminated with persistent agents; many of the fatalities after the explosion of a WWII US ammunition ship carrying mustard gas, in the harbor of Bari, Italy, after a German bombing on 2 December 1943, came when rescue workers, not knowing of the contamination, bundled cold, wet seamen in tight-fitting blankets.

For decontaminating equipment and building exposed to persistent agents, such as blister agents and VX, some special equipment and materials will be needed. Some type of neutralizing spray will be needed, which, with the less toxic agents such as chlorine, can be a strong water spray. In other cases, a specific chemical decontaminant will be required (FM 34.21).

While the study of chemicals and their military uses was widespread in China, the use of toxic materials has historically been viewed with mixed emotions and some disdain in the West.

One of the earliest reactions to the use of chemical agents was from Rome. Struggling to defend themselves from the Roman legions, Germanic tribes poisoned the wells of their enemies, with Roman jurists having been recorded as declaring "armis bella non venenis geri", meaning "war is fought with weapons, not with poisons."

Before 1915 the use of poisonous chemicals in battle was typically the result of local initiative, and not the result of an active government chemical weapons program. There are many reports of the isolated use of chemical agents in individual battles or sieges, but there was no true tradition of their use outside of incendiaries and smoke. Despite this tendency, there have been several attempts to initiate large-scale implementation of poison gas in several wars, but with the notable exception of World War I, the responsible authorities generally rejected the proposals for ethical reasons.

For example, in 1854 Lyon Playfair, a British chemist, proposed using a cyanide-filled artillery shell against enemy ships during the Crimean War. The British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy."

• August 27, 1874: The Brussels Declaration Concerning the Laws and Customs of War is signed, specifically forbidding the "employment of poison or poisoned weapons."
• September 4, 1900: The Hague Conference, which includes a declaration banning the "use of projectiles the object of which is the diffusion of asphyxiating or deleterious gases," enters into force.
• February 6, 1922: After World War I, the Washington Arms Conference Treaty prohibited the use of asphyxiating, poisonous or other gases. It was signed by the United States, Britain, Japan, France, and Italy, but France objected to other provisions in the treaty and it never went into effect.
• September 7, 1929: The Geneva Protocol enters into force, prohibiting the use of poison

Main article: Chemical weapon proliferation

Despite numerous efforts to reduce or eliminate them, some nations continue to research and/or stockpile chemical warfare agents. To the right is a summary of the nations that have either declared weapon stockpiles or are suspected of secretly stockpiling or possessing CW research programs. Notable examples include China.

According to the testimony of Assistant Secretary of State for Intelligence and Research Carl W. Ford before the Senate Committee on Foreign Relations, it is very probable that China has an advanced chemical warfare program, including research and development, production, and weaponization capabilities. Furthermore, there is considerable concern from the US regarding China's contact and sharing of chemical weapons expertise with other states of proliferation concern, including Syria and Iran.

Chemical weapons have been used for millennia in the form of poisoned arrows, but evidence can be found for the existence of more advanced forms of chemical weapons in ancient and classical times.

A good example of early chemical warfare was the late Stone Age (10 000 BC) hunter-gatherer societies in Southern Africa, known as the San. They used poisoned arrows, tipping the wood, bone and stone tips of their arrows with poisons obtained from their natural environment. These poisons were mainly derived from scorpion or snake venom, but it is believed that some poisonous plants were also utilized. The arrow was fired into the target of choice, usually an antelope (the favourite being an eland), with the hunter then tracking the doomed animal until the poison caused its collapse.

The earliest surviving references to toxic warfare are possibly those in the Indian epics Ramayana and Mahabharata. The Manusmriti book of laws also forbids use of poison weapons.^[10]

Dating from the 4th century BC, writings of the Mohist sect in China describe the use of bellows to pump smoke from burning balls of mustard and other toxic vegetables into tunnels being dug by a besieging army. Even older Chinese writings dating back to about 1000 BC contain hundreds of recipes for the production of poisonous or irritating smokes for use in war along with numerous accounts of their use. From these accounts we know of the arsenic-containing "soul-hunting fog", and the use of finely divided lime dispersed into the air to suppress a peasant revolt in AD 178.

The earliest recorded use of gas warfare in the West dates back to the 5th century BC, during the Peloponnesian War between Athens and Sparta. Spartan forces besieging an Athenian city placed a lighted mixture of wood, pitch, and sulfur under the walls hoping that the noxious smoke would incapacitate the Athenians, so that they would not be able to resist the assault that followed. Sparta wasn't alone in its use of unconventional tactics during these wars: Solon of Athens is said to have used hellebore roots to poison the water in an aqueduct leading from the Pleistrus River around 590 BC during the siege of Cirrha.

Chemical weapons were known and used in ancient and medieval China. Polish chronicler Jan Długosz mentions usage of posionous gas by Mongol army in 1241 in Battle of Legnica.

During the Renaissance, people again considered using chemical warfare. One of the earliest such references is from Leonardo da Vinci, who proposed a powder of sulfide of arsenic and verdigris in the 15th century:

throw poison in the form of powder upon galleys. Chalk, fine sulfide of arsenic, and powdered verdegris may be thrown among enemy ships by means of small mangonels, and all those who, as they breathe, inhale the powder into their lungs will become asphyxiated.

It is unknown whether this powder was ever actually used.

In the 17th century during sieges, armies attempted to start fires by launching incendiary shells filled with sulphur, tallow, rosin, turpentine, saltpeter, and/or antimony. Even when fires were not started, the resulting smoke and fumes provided a considerable distraction. Although their primary function was never abandoned, a variety of fills for shells were developed to maximize the effects of the smoke.

In 1672, during his siege of the city of Groningen, Christoph Bernhard van Galen, the Bishop of Münster, employed several different explosive and incendiary devices, some of which had a fill that included belladonna, intended to produce toxic fumes. Just three years later, August 27, 1675, the French and the Germans concluded the Strasbourg Agreement, which included an article banning the use of "perfidious and odious" toxic devices.

In 1854, Lyon Playfair, a British chemist, proposed a cacodyl cyanide artillery shell for use against enemy ships as way to solve the stalemate during the siege of Sevastopol. The proposal was backed by Admiral Thomas Cochrane of the Royal Navy. It was considered by the Prime Minister, Lord Palmerston, but the British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy." Playfair’s response was used to justify chemical warfare into the next century:

There was no sense in this objection. It is considered a legitimate mode of warfare to fill shells with molten metal which scatters among the enemy, and produced the most frightful modes of death. Why a poisonous vapor which would kill men without suffering is to be considered illegitimate warfare is incomprehensible. War is destruction, and the more destructive it can be made with the least suffering the sooner will be ended that barbarous method of protecting national rights. No doubt in time chemistry will be used to lessen the suffering of combatants, and even of criminals condemned to death.

Later, during the American Civil War, New York school teacher John Doughty proposed the offensive use of chlorine gas, delivered by filling a 10 inch (254 millimeter) artillery shell with 2 to 3 quarts (2 to 3 liters) of liquid chlorine, which could produce many cubic feet (a few cubic meters) of chlorine gas. Doughty’s plan was apparently never acted on, as it was probably presented to Brigadier General James Wolfe Ripley, Chief of Ordnance, who was described as being congenitally immune to new ideas.

A general concern over the use of poison gas manifested itself in 1899 at the Hague Conference with a proposal prohibiting shells filled with asphyxiating gas. The proposal was passed, despite a single dissenting vote from the United States. The American representative, Navy Captain Alfred Thayer Mahan, justified voting against the measure on the grounds that "the inventiveness of Americans should not be restricted in the development of new weapons."

A soldier with mustard gas burns, ca. 1917–1918.

Main article: Poison gas in World War I

The French were the first to use chemical weapons during the First World War, using tear gas. The German's first use of chemical weapons were shells containing xylyl bromide that were fired at the Russians near the town of Bolimów, Poland in January 1915.^[11] The first full-scale deployment of chemical warfare agents was during World War I, originating in the Second Battle of Ypres, April 22, 1915, when the Germans attacked French, Canadian and Algerian troops with chlorine gas. Deaths were light, though casualties relatively heavy. A total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine, phosgene and mustard gas. Official figures declare about 1,176,500 non-fatal casualties and 85,000 fatalities directly caused by chemical warfare agents during the course of the war.

To this day unexploded WWI-era chemical ammunition is still frequently uncovered when the ground is dug in former battle or depot areas and continues to pose a threat to the civilian population in Belgium and France and less commonly in other countries. The French and Belgian governments have had to launch special programs for treating discovered ammunition.

After the war, most of the unused German chemical warfare agents were dumped into the Baltic Sea, a common disposal method among all the participants in several bodies of water. Over time, the salt water causes the shell casings to corrode, and mustard gas occasionally leaks from these containers and washes onto shore as a wax-like solid resembling ambergris. Even in this solidified form, the agent is active enough to cause severe contact burns to anybody coming into contact with it.

Dressing the Wounded during a Gas Attack, a 1918 painting by the British war artist Austin Osman Spare.

After World War I chemical agents were occasionally used to subdue populations and suppress rebellion.

Following the defeat of the Ottoman Empire in 1917, the Ottoman government collapsed completely, and the former empire was divided amongst the victorious powers in the Treaty of Sèvres. The British occupied Mesopotamia (present-day Iraq) and established a colonial government.

In 1920, the Arab and Kurdish people of Mesopotamia revolted against the British occupation, which cost the British dearly. As the Mesopotamian resistance gained strength, the British resorted to increasingly repressive measures. Much speculation was made about aerial bombardment of major cities with gas in Mesopotamia, with Winston Churchill, then-Secretary of State at the British War Office, arguing in favor of it. In the 1920s generals reported that poison had never won a battle. The soldiers said they hated it and hated the gas masks. Only the chemists spoke out to say it was a good weapon.

In 1925, sixteen of the world's major nations signed the Geneva Protocol, thereby pledging never to use gas in warfare again. Notably, in the United States, the Protocol languished in the Senate until 1975, when it was finally ratified.

The Soviet Union also employed poison gas on its own people in 1921 during peasant Tambov Rebellion. An order signed by military commanders Tukhachevsky and Vladimir Antonov-Ovseenko stipulated: "The forests where the bandits are hiding are to be cleared by the use of poison gas. This must be carefully calculated, so that the layer of gas penetrates the forests and kills everyone hiding there."^[12]

During the Rif War in Spanish Morocco in 1921–1927, combined Spanish and French forces dropped mustard gas bombs in an attempt to put down the Berber rebellion. (See also: Chemical weapons in the Rif War)

In 1935 Fascist Italy used mustard gas during the invasion of Ethiopia in the Second Italo-Abyssinian War. Ignoring the Geneva Protocol, which it signed seven years earlier, the Italian military dropped mustard gas in bombs, sprayed it from airplanes, and spread it in powdered form on the ground. 15,000 chemical casualties were reported, mostly from mustard gas.

The chemical structure of Sarin nerve gas, discovered by Germany in 1938.

Despite article 171 of the Versailles Peace Treaty and a resolution adopted against Japan by the League of nations on 14 May 1938, the Imperial Japanese Army frequently used chemical weapons. By fear of retaliation however, those weapons were never used against Occidentals but against other Orientals judged "inferior" by the imperial propaganda. According to historians Yoshiaki Yoshimi and Seiya Matsuno, the chemical weapons were authorized by specific orders given by emperor Showa himself, transmitted by the chief of staff of the army. For example, the Emperor authorized the use of toxic gas on 375 separate occasions during the battle of Wuhan from August to October 1938.^[13] They were also profusely used during the invasion of Changde.

The Imperial Japanese Army used mustard gas and the recently-developed blister agent Lewisite against Chinese troops and guerillas. During these attacks, the Japanese also employed biological warfare by intentionally spreading cholera, dysentery, typhoid, bubonic plague, and anthrax produced by Unit 731. Experiments involving chemical weapons were conducted on live prisoners (Unit 731 and Unit 516). As of 2005, 60 years after the end of the war, canisters that were abandoned by Japan in their hasty retreat are still being dug up in construction sites, causing injuries and allegedly even deaths^{[citation needed]}.

During World War II, chemical warfare was revolutionized by Nazi Germany's accidental discovery of the nerve agents tabun and sarin by Gerhard Schrader, a chemist of IG Farben. The nerve agent soman was discovered by Nobel Prize laureate Richard Kuhn and his collaborator Konrad Henkel at the Kaiser Wilhelm Institute for Medical Research in Heidelberg in spring of 1944 (see Schmaltz 2005; Schmaltz 2006). The Nazis developed and manufactured large quantities of several agents, but chemical warfare was not extensively used by either side though chemical troops were set up (in Germany since 1934) and delivery technology was actively developed. Recovered Nazi documents suggest that German intelligence incorrectly thought that the Allies also knew of these compounds, interpreting their lack of mention in the Allies' scientific journals as evidence that information about them was being suppressed. Germany ultimately decided not to use the new nerve agents, fearing a potentially devastating Allied retaliatory nerve agent deployment.

William L. Shirer, in The Rise and Fall of the Third Reich, writes that the British high command considered the use of chemical weapons as a last-ditch defensive measure in the event of a Nazi invasion of Britain.

On the night of December 2, 1943, German Ju 88 bombers attacked the port of Bari in Southern Italy, sinking several American ships — among them SS John Harvey, which was carrying mustard gas intended for use in retaliation by the Allies if German forces initiated gas warfare. The presence of the gas was highly classified, and authorities ashore had no knowledge of it — which increased the number of fatalities, since physicians, who had no idea that they were dealing with the effects of mustard gas, prescribed treatment improper for those suffering from exposure and immersion.

The whole affair was kept secret at the time and for many years after the war (in the opinion of some, there was a deliberate and systematic cover-up). According to the U.S. military account, "Sixty-nine deaths were attributed in whole or in part to the mustard gas, most of them American merchant seamen"^[14] out of 628 mustard gas military casualties.^[15] The large number of civilian casualties among the Italian population were not recorded. Part of the confusion and controversy derives from the fact that the German attack was highly destructive and lethal in itself, also apart from the accidental additional effects of the gas (it was nicknamed "The Little Pearl Harbor"), and attribution of the causes of death between the gas and other causes is far from easy. The affair is the subject of two books: Disaster at Bari by Glenn B. Infield and Nightmare in Bari: The World War II Liberty Ship Poison Gas Disaster and Coverup by Gerald Reminick.

Rick Atkinson, in his book The Day of Battle, describes the intelligence that prompted Allied leaders to deploy mustard gas to Italy. This included Italian intelligence that Adolf Hitler had threatened to use gas against Italy if Italy changed sides and prisoner of war interrogations suggesting that preparations were being made to use a "new, egregiously potent gas" if the war turned decisevely against Germany. Atkinson concludes that "No commander in 1943 could be cavalier about a manifest threat by Germany to use gas."

Although chemical weapons were not intentionally deployed on a large scale during on the front lines of the European Theatre of World War II, there were some recorded uses of them by the Axis Powers, when retaliation was not feared:

• In 1944, the Grand Mufti of Jerusalem, Amin al-Husayni, the senior Islamic religious authority of the Palestinian Arabs and close ally of Adolf Hitler, sponsored an unsuccessful chemical warfare assault on the Jewish community in Palestine. Five parachutists were supplied with maps of Tel Aviv, canisters of a German–manufactured "fine white powder," and instructions from the Mufti to dump chemicals into the Tel Aviv water system. District police commander Fayiz Bey Idrissi later recalled, "The laboratory report stated that each container held enough poison to kill 25,000 people, and there were at least ten containers."^[16]

• During the Holocaust, the Nazis used the insecticide Zyklon B, which contains hydrogen cyanide, to kill several million people in extermination camps such as Auschwitz and Majdanek. Tear and reportedly poison gasses were used by against civilian and guerilla shelters during the Warsaw Ghetto Uprising in 1943, and again against sewer lines of communication during the Warsaw Uprising in 1944. In the concentration camp Struthof-Natzweiler in occupied Alsace the German physicians August Hirt and Otto Bickenbach conducted human experiments with mustard gas and phosgene on inmates to test possible prophylactic and therapeutic treatments causing injuries and death of many prisoners.

After World War II, the Allies recovered German artillery shells containing the three German nerve agents of the day (tabun, sarin, and soman), prompting further research into nerve agents by all of the former Allies. Although the threat of global thermonuclear annihilation was foremost in the minds of most during the Cold War, both the Soviet and Western governments put enormous resources into developing chemical and biological weapons.

In 1952, researchers in Porton Down, England, invented the VX nerve agent but soon abandoned the project. In 1958 the British government traded their VX technology with the United States in exchange for information on thermonuclear weapons; by 1961 the U.S. was producing large amounts of VX and performing its own nerve agent research. This research produced at least three more agents; the four agents (VE, VG, VM, VX) are collectively known as the "V-Series" class of nerve agents.

Also in 1952 the U.S. Army patented a process for the "Preparation of Toxic Ricin", publishing a method of producing this powerful toxin.

During the 1960s, the U.S. explored the use of anticholinergic deleriant incapacitating agents. One of these agents, assigned the weapon designation BZ, was allegedly used experimentally in the Vietnam War. These allegations inspired the 1990 fictional film Jacob's Ladder.

Between 1967 and 1968, the U.S. decided to dispose of obsolete chemical weapons in an operation called Operation CHASE, which stood for "cut holes and sink 'em." Several shiploads of chemical and conventional weapons were put aboard old Liberty ships and sunk at sea.

In 1969, 23 U.S. servicemen and one U.S. civilian stationed in Okinawa, Japan, were exposed to low levels of the nerve agent sarin while repainting the depots' buildings. The weapons had been kept secret from Japan, sparking a furor in that country and an international incident. These munitions were moved in 1971 to Johnston Atoll under Operation Red Hat.

A UN working group began work on chemical disarmament in 1980. On April 4, 1984, U.S. President Ronald Reagan called for an international ban on chemical weapons. U.S. President George H.W. Bush and Soviet Union leader Mikhail Gorbachev signed a bilateral treaty on June 1, 1990, to end chemical weapon production and start destroying each of their nation's stockpiles. The multilateral Chemical Weapons Convention (CWC) was signed in 1993 and entered into force (EIF) in 1997.

On April 19, 1993 the FBI injected non-lethal CS grenades into wooden buildings during the Waco Siege. None of the Davidians left their building, however. CS is flammable and may have helped fuel the fires which later started. All the buildings within the site burned to the ground but few members tried to escape. Several of the bodies recovered after the raid had lethal doses of cyanide, a byproduct of burning CS.^{[citation needed]}

A 1994 United States Senate Report, entitled "Is military research hazardous to veterans health? Lessons spanning a half century,"^[17] detailed the United States Department of Defense's practice of experimenting on animal and human subjects, often without the latter's knowledge or consent.^[18] This included:

• Approximately 60,000 [US] military personnel were used as human subjects in the 1940s to test the chemical agents mustard gas and lewisite.^[19]
• Between the 1950s through the 1970s, at least 2,200 military personnel were subjected to various biological agents, referred to as Operation Whitecoat. Unlike most of the studies discussed in this report, Operation Whitecoat was truly voluntary.^[20]
• Between 1951 and 1969, Dugway Proving Ground was the site of testing for various chemical and biological agents, including an open air aerodynamic dissemination test in 1968 that accidentally killed, on neighboring farms, approximately 6,400 sheep by an unspecified nerve agent.^[21]

Due to the secrecy of the Soviet Union's government, very little information was available about the direction and progress of the Soviet chemical weapons until relatively recently. After the fall of the Soviet Union, Russian chemist Vil Mirzayanov published articles revealing illegal chemical weapons experimentation in Russia. In 1993, Mirzayanov was imprisoned and fired from his job at the State Research Institute of Organic Chemistry and Technology, where he had worked for 26 years. In March of 1994, after a major campaign by U.S. scientists on his behalf, Mirzayanov was released.^[22]

Among the information related by Vil Mirzayanov was the direction of Soviet research into the development of even more toxic nerve agents, which saw most of its success during the mid-1980s. Several highly toxic agents were developed during this period; the only unclassified information regarding these agents is that they are known in the open literature only as "Foliant" agents (named after the program under which they were developed) and by various code designations, such as A-230 and A-232.^[23]

According to Mirzayanov, the Soviets also developed agents that were safer to handle, leading to the development of the so-called binary weapons, in which precursors for the nerve agents are mixed in a munition to produce the agent just prior to its use. Because the precursors are generally significantly less hazardous than the agents themselves, this technique makes handling and transporting the munitions a great deal simpler. Additionally, precursors to the agents are usually much easier to stabilize than the agents themselves, so this technique also made it possible to increase the shelf life of the agents a great deal. During the 1980s and 1990s, binary versions of several Soviet agents were developed and are designated as "Novichok" agents (after the Russian word for "newcomer").^[24] Together with Lev Fedorov, he told the secret Novichok story exposed in the newspaper Moscow News.^[25]

Victims of Iraq's poison gas attack in civil area during Iran-Iraq war . Chemical weapons which had been delivered to Saddam killed and injured numerous Iranian and Iraqis. According to Iraqi documents, assistance in developing chemical weapons was obtained from firms in many countries, including the United States, West Germany, the Netherlands, the United Kingdom, France and China.^[26]

The Iran-Iraq War began in 1980 when Iraq attacked Iran. Early in the conflict, Iraq began to employ mustard gas and tabun delivered by bombs dropped from airplanes; approximately 5% of all Iranian casualties are directly attributable to the use of these agents.

About 100,000 Iranian soldiers were victims of Iraq's chemical attacks. Many were hit by mustard gas. The official estimate does not include the civilian population contaminated in bordering towns or the children and relatives of veterans, many of whom have developed blood, lung and skin complications, according to the Organization for Veterans. Nerve gas agents killed about 20,000 Iranian soldiers immediately, according to official reports. Of the 80,000 survi