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chemical warfare

Warfare and associated military operations involving the employment of lethal and incapacitating munitions and agents, typically poisons, contaminants, and irritants.

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World of the Body: chemical warfare

Wilfred Owen, veteran and poet of World War I, understood chemical warfare. Dulce et decorum est, Owen's view of gassing by chlorine, sums it up:

Gas! Gas! Quick, boys — An ecstasy of fumbling
Fitting the clumsy helmets just in time,
But someone still was yelling out and stumbling
And flound'ring like a man in fire or lime…

Chemical warfare has evolved since then: from the asphyxiating chlorine; through the irritant, skin penetrating and bone marrow damaging mustard gas; to the acutely toxic skin-and inhalation-hazard nerve poisons — by-products of research on insecticidal organophosphate chemicals in the late 1930s. En route, and since, thousands of chemicals have been screened for their use in war, but the inventory of established chemical warfare agents remains at about twenty.

In parallel with the search for yet more effective agents, research has continued on antidotes and other means of protection. The modern infantryman has protective suits, gas masks, sensitive detectors, and injectable antidotes (but only to nerve poisons). Vehicles with air filtration units, and mobile hospitals with decontamination facilities, offer protection for other service units, the main objective being to avoid contact with the chemical agent.

Antidotes and hospitalization are no guarantees of a successful recovery following exposure to tabun, sarin, soman, or VX — nerve agents all, and capable at low concentrations of disrupting nerve transmission and the ability to breathe. Nerve agents can kill within minutes after inhalation, and in less than an hour following skin contact. For all chemical warfare agents the degree of injury and subsequent disability depends on the quantity of chemical inhaled or in contact with the skin.

Wilfred Owen captured the terror of chemical warfare, and his fumblers made up a sizeable proportion of the 1.3 million casualties it caused in World War I. Others fell victim because they had either no gas masks, or faulty masks, and latterly, inadequate skin protection when Germany introduced mustard gas in 1917. Some 27 000 servicemen died from the effects of chemical agents in World War I. This ratio of deaths to injuries, lower than with conventional munitions, led some to argue that chemical warfare was a more humane way of fighting.

Civilian casualties, caused by chemical agents being blown beyond the battlefields of northern France and Belgium border villages, numbered roughly 1000. Most civilians survived their ordeal, with some 110-120 deaths being recorded. Approximately 4000 factory workers in Britain, France, and the US were injured during the manufacture of chemical munitions between 1916-18. Iranian and Kurdish victims of Iraq's use of mustard gas and nerve agents in the 1980s were less fortunate. Tens of thousands, largely civilians, were injured, but a high percentage died, some 5000 in the Kurdish city of Halabja alone, according to estimates.

Unlike soldiers, civilians have relatively little protection against chemical warfare agents. The training provided to soldiers equips them, in part, for fighting in a chemical environment. Much of their training is to prevent any fumbling and to overcome the sense of isolation in their protective suits.

Remaining upwind, above ground level, and in a sealed room with an adequate air supply, will provide protection for civilians — if they have time to prepare. Iraq's Kurds had no warning, and the extensive casualties caused by chemical agents caused great panic and led to millions fleeing their homes to seek shelter in neighbouring countries.

The plight of the Kurds galvanized discussions on a chemical disarmament regime. Although most countries are signatories to the 1925 Geneva Protocol, which outlaws (first) use of chemical and biological warfare, this treaty does not forbid retaliation, nor does it have any policing powers. The 1993 Chemical Weapons Convention (CWC) remedies these deficiencies. Following ratification in the parliaments of 65 countries, the convention became international law in April 1997. Well over 120 countries have now ratified the Convention and agree to neither use, make, nor encourage others to produce chemical weapons. As proof of their good intentions all ratifiers have also agreed to inspection, at short notice, of any site, be it military base, chemical manufacturing plant, or area where agents may have been used. Adoption of the Convention requires countries such as the US, with some 30 000 tonnes of chemical agents, and Russia, with some 40 000 tonnes, to destroy all stocks within 10 years. The bill for Russia to comply with these provisions is an estimated $4 billion.

Details about stockpiles, sites, inventories of chemicals, and manufacturing locations are transmitted by governments to the Organisation for the Prohibition of Chemical Weapons (OPCW), based in the Hague. The OPCW oversees the CWC and organizes inspections.

Only two other countries, India and Iraq, are definitely known to have stocks of usable chemical munitions. India has ratified the Chemical Weapons Convention, Iraq has not. Following her defeat in the second Gulf War in 1991, Iraq has agreed to a United Nations Special Commission (UNSCOM) inspecting sites and destroying munitions and chemical and biological warfare manufacturing facilities. UNSCOM never completed this programme. Iraq expelled the UNSCOM team following bombing of the country by the US and the UK in 1999. Negotiations are continuing between Iraq and the UN about a new type of inspection regime.

A number of other countries, including Britain, France, and Italy, have declared that they possess some chemical warfare munitions, many of which were made before 1945. Small stocks of these munitions may be buried on disused military bases, and finding them will probably be more a chance event than the result of a specific investigation. In consequence, countries possessing stocks of these older, largely unusable munitions will have more than 10 years in which to destroy them.

Iraq brought chemical warfare up to date. The most extensive use, prior to this, of chemicals deliberately intended to injure or kill humans occurred between 1915-18. In the intervening years chemical agents have been used in other wars. Italy used mustard gas against Ethiopian forces in 1935-6. Japan is alleged to have used mustard gas against Chinese forces in 1938. In 1967, Britain claimed that an asphyxiating chemical agent had been used by Egypt against Yemeni troops.

Chemical warfare, however, is not only about lethal agents. Many countries adhere to the view that the use of chemical defoliants by the US in the Vietnam War both to remove the forest canopy and to destroy food crops was also chemical warfare. The US disagrees with this interpretation. Defoliants used in Vietnam caused a rapid leaf drop, increasing visibility in large swathes of inland and coastal forests. Destruction of forests and food crops caused considerable hardship in the locality. Regrettably, the concentrations of the chemicals used resulted in the loss of countless trees, and forests being replaced by grassland. The destruction is still evident today.

Riot control agents have also been used in warfare to force combatants to leave entrenched positions, exposing them to enemy fire. Use of riot-control agents in this context also constitutes chemical warfare. The CWC acknowledges this, and the use of riot control agents in war is now forbidden.

A disarmament treaty to prevent chemical warfare is now in place. Negotiations to secure it have taken almost 20 years. More countries are expected to ratify the CWC. Persuading all nations to do so and to follow the new rules is the ultimate goal.

— Alastair Hay

See also poisons; war and the body.

US Military Dictionary: chemical warfare

All aspects of military operations involving the employment of lethal and incapacitating munitions/agents and the warning and protective measures associated with such offensive operations.

See the Introduction, Abbreviations and Pronunciation for further details.

Britannica Concise Encyclopedia: chemical warfare

Use of lethal or incapacitating chemical weapons in war, and the methods of combating such agents. Chemical weapons include choking agents such as the chlorine and phosgene gas employed first by the Germans and later by the Allies in World War I; blood agents such as hydrogen cyanide or cyanogen gas, which block red blood cells from taking up oxygen; blister agents such as sulfur gas and Lewisite, also dispensed as a gas, which burn and blister the skin; and nerve agents such as Tabun, Sarin, Soman, and VX, which block the transmission of nerve impulses to the muscles, heart, and diaphragm. The horrific casualties suffered in World War I led to the 1925 Geneva Protocol, which made it illegal to employ chemical weapons but did not ban their production. Chemical weapons were used a number of times afterward, most notably by Italy in Ethiopia (1935 – 36), by Japan in China (1938 – 42), by Egypt in Yemen (1966 – 67), and by Iran and Iraq against each other (1984 – 88). During the Cold War the Soviet Union and U.S. built up enormous chemical arsenals; these were dismantled under the terms of the 1993 Chemical Weapons Convention, which prohibits all development, production, acquisition, stockpiling, or transfer of such weapons. Not all countries have signed the convention, and many are suspected of pursuing clandestine chemical programs. Many military forces have adopted various defensive measures, including chemical sensors, protective garments and gas masks, decontaminants, and injectable antidotes, and some have reserved the option of retaliating in kind to any chemical attack. In 1995 a religious cult killed 12 civilians and injured thousands more with Sarin gas in Tokyo; this pointed out the power of chemical agents as weapons of terror as well as the difficulty of protecting civilian populations. See also biological warfare.

For more information on chemical warfare, visit Britannica.com.

Columbia Encyclopedia: chemical warfare,

employment in war of incendiaries, poison gases, and other chemical substances. Ancient armies attacking or defending fortified cities threw burning oil and fireballs. A primitive type of flamethrower was employed as early as the 5th cent. B.C.; modern types are still in use. In the Middle Ages, before the introduction of gunpowder, a flammable composition known as Greek fire was used. Smoke from burning straw or other material was employed in early times, but its effectiveness is uncertain.

Poison gas was first used during World War I, when the Germans released (Apr., 1915) chlorine gas against the Allies. The Germans also introduced mustard gas later in the war. Afterward, the major powers continued to stockpile gases for possible future use and several actually used it: the British in Afghanistan, the French and Spanish in Africa, the Italians in Ethiopia, and the Japanese in China. Lethal gases were not employed in combat during World War II, but the Germans did use gases for mass murder during the Holocaust. The Germans also invented and stockpiled the first nerve gas. It is odorless and colorless and attacks the body muscles, including the involuntary muscles. It is the most lethal and insidious weapon of chemical warfare. Since World War II, chemical weapons are known to have been used by Egypt in Yemen (during the 1962–67 civil war) and by Iraq against Iran during the Iran-Traq War and against Kurdish rebels.

Besides lethal gases, which attack the skin, blood, nervous, or respiratory system and require hospitalization of the victim, there are also nonlethal incapacitating agents, which, like tear gas, cause temporary physical disability. Such agents have often been employed in riot control, espionage, and warfare. Various forms of herbicides and defoliants are also used to destroy crops or vegetation, as Agent Orange was used by the United States during the Vietnam War.

The potential effectiveness of chemical warfare is increasing with improved methods of dissemination, such as artillery shells, grenades, missiles, and aircraft and submarine spray guns. Some protection against chemical weapons is possible using suits, sealed vehicles, and shelters. Such countermeasures usually protect against nuclear fallout and biological warfare as well. Lethal chemical weapons are held by many nations and they continue to be used. The danger of the proliferation of chemical and biological weapons remains despite arms control because they are relatively easy to manufacture and deploy.

Efforts to control chemical and biological weapons began in the late 19th cent. The Geneva Protocol of 1925, which went into force in 1928, condemned the use of chemical weapons but did not ban the development and stockpiling of chemical weapons. The United States did not ratify the protocol until 1974. In 1990, with the end of the cold war, the United States and the Soviet Union agreed to cut their arsenals by 80% in an effort to create a climate of change that would discourage smaller nations from stockpiling and using such lethal weapons. In 1993 a international treaty banning the production, stockpiling (both by 2007), and use of chemical weapons and calling for the establishment of an independent organization to verify compliance was adopted. The agreement, which became effective in 1997, has been signed and ratified by 160 nations. The treaty is enforced by the Organization for the Prohibition of Chemical Weapons, which is based in The Hague. The alleged Iraqi retention, after the Persian Gulf War cease-fire, of chemical weapons and other weapons of mass destruction was the main pretext for the 2003 U.S.-British invasion of Iraq.

Bibliography

See the ongoing Stockholm International Peace Research Institute (SIPRI), The Problems of Chemical and Biological Warfare (1971–); R. Harris and J. Paxman, A Higher Form of Killing (1982); E. M. Spiers, Chemical Warfare (1986); J. B. Tucker, War of Nerves (2006).

Intelligence Encyclopedia: Chemical Warfare

Chemical warfare involves the aggressive use of bulk chemicals that cause death or grave injury. These chemicals are different from the lethal chemical compounds that are part of infectious bacteria or viruses. The latter constitute biological warfare.

History of Chemical Warfare

The use of chemicals in warfare began centuries ago, when early combatants learned that smoke from burning sulfur caused discomfort when it drifted into enemy fortifications. The dawn of modern chemical warfare occurred during World War I. On April 15, 1915, German forces released about 160 tons of chlorine gas into the wind near the Belgian village of Ypres. The clouds of the gas drifted into Allied forces, killing some 5,000 soldiers. Two days later, another chlorine attack at the same village killed 5,000 more soldiers.

During the remainder of World War I, German and British forces used chlorine gas, and other chemicals (i.e., mustard gas and phosphene) with increasing tendency. Estimates are that approximately 113,000 tons of chemical weapons were used from 1915 to 1918, killing some 92,000 people and injuring over one million people.

The aerial release of chemicals brought unpredictable results at the mercy of prevailing winds. Shifting winds could send the deadly cloud back to the attacking troops. Later during World War I, more sophisticated use of chemical weapons began. For example, the French used shells filled with an irritant to the eyes, skin, and lining of the nose and lungs, and the Germans fired lead balls coated with similar irritant.

The horrors of chemical warfare during World War I prompted the drafting of the Geneva Protocol of 1925, which banned chemical and biological weapons of warfare. The protocol was initially signed by 38 nations (now over 130 nations). As history has shown, the protocol has not stopped the use of such weapons by rouge states or fringe elements in order to commit terrorism.

Aerial releases of lethal chemicals did not occur in World War II. However, the Germans developed a new class of chemical weapon called nerve agents. During the 1930s and 1940s, agents such as Tabun, Sarin, and Soman were created.

Chemical warfare research continued during the Cold War tensions during the 1950s. During this time, military chemists in the United Kingdom and then in the United States adapted insecticides to produce the most lethal chemical agent then known. The agent was code named VX. The potency of VX was accidentally demonstrated in 1968, when a testing accident at the VX manufacturing plant in Dugway, Utah killed over 6,000 sheep.

During the Vietnam War of the 1970s, the U.S. use of defoliants—chemicals that killed vegetation, permitting a clearer detection of the enemy—was extensive. One of these compounds, Agent Orange, has become infamous as the alleged cause of a variety of physical ailments in veterans of the conflict.

In the last few decades, chemicals have become the tools of terrorists. A particularly well-known example is the release of Sarin gas into the Tokyo subway system by the religious cult Aum Shinrikyo in March of 1995. The gas killed 12 people and injured over 5,500 people in 16 stations.

Chemical Warfare Agents

There are several classes of chemical warfare agents, based on their effects

compounds that cause choking or that irritate the lungs,
blister agents (also called vesicants),
blood agents,
nerve agents,
herbicides, and

incendiaries

Choking and irritant agents. There are a number of compounds that cause choking or irritation of lung tissue. Examples include chlorine, phosgene (carbonyl chloride), diphosgene, chloropicrin, ethyldichloroarsine, and perflurorisobutylene.

Chlorine gas is suffocating and quickly burns tissues in the nose, mouth, and lungs. The burned tissue can die and slough off, causing lasting damage. Chlorine gas dissipates in the air very quickly. If exposure is not too long, than damage can be minor. In contrast, the compound called disphosgene is a liquid at room temperature, and so persists much longer.

Blister agents. As their name implies, blister agents cause the formation of large and painful blisters on the skin. Eye and lung tissue can also be damaged. A well-known example of a blistering agent dating from World War I is mustard gas. The damage to cells of the skin cause blistering up to 24 hours after exposure to mustard gas. These blisters take a long time to heal and can send the body into a lethal shock reaction.

Other examples of blistering agents include nitrogen mustard, lewisite, and phenyldichloroarsine. The latter compound is a liquid, which can be sprayed onto an enemy or released from a balloon, helicopter, or airplane.

Blood agents. These compounds interfere with the body's ability to transport oxygen in the bloodstream. This is done by either blocking the use of oxygen by cells in the body or by blocking the ability of the blood to take up the oxygen. Examples include hydrogen cyanide (also called prussic acid), cyanogen chloride, arsine, carbon monoxide, and hydrogen sulfide.

Hydrogen cyanide is initially a liquid at room temperature, but it quickly evaporates. This compound is noteworthy in recent world history, as it was used by Iraq in 1988 on an attack on the Kurdish town of Halabja during the Iran-Iraq war. Because of its past use by Iraq, hydrogen cyanide was one of the major concerns of United Nations inspectors who inspected various facilities in Iraq during the winter of 2003.

Compounds such as arsine and carbon monoxide destroy the ability of the hemoglobin component of the blood to bind oxygen. Arsine does this by destroying the red blood cells. Carbon monoxide binds to hemoglobin, blocking the binding of oxygen.

Nerve agents. Compounds that are classified as nerve agents interfere with the body's transmission of nerve impulses. This is done by disrupting the activity of a chemical called acetyl cholinesterase, which functions to bridge the gap between adjacent nerve cells, permitting an electrical nerve signal to pass from one nerve cell to the next.

Nerve agents were first developed in 1936, following the development of organophosphate types of pesticides. The first nerve agent that was made is called Tabrun. It is a member of what is known as the G series of nerve agents. Other G series members are Sarin and Soman. Sarin is particularly lethal; a small amount absorbed through the skin can kill a man within two minutes. When inhaled, death occurs within 15 minutes. Sarin is infamous as the gas released into the Tokyo subway system by the fringe group Aum Shinrikyo in 1995.

Another series of nerve agents are called the V series. Members of this series—which are commonly abbreviated according to their chemical composition—are more potent than the agents of the G series. As well, they persist longer in the environment. They can, for example, be applied to surfaces like roads as a slime.

Examples of V series agents include VX, VE, VG, and VM. VX is extremely potent; a drop of the liquid absorbed through the skin is lethal within a few hours without treatment.

Nerve agents can be contained in missiles or in canisters for lengthy time periods. Examination of caves in Afghanistan that were used as strongholds by the terrorist group al Qaeda has revealed evidence of stores of Sarin and VX.

Herbicides. Herbicides are chemicals that kill vegetation. Such chemicals are often used in everyday life to keep lawns free of weeds (although more environmentallyfriendly alternatives are becoming popular). When used in war, herbicides are weapons of mass destruction to foliage. Destruction of plants and the resulting loss of leaf cover remove much of the concealment for an enemy in a forested area. These philosophies led to the massive use of Agent Orange by the United States in the Vietnam War in the 1970s. Since that war, the damaging effects of herbicides like Agent Orange and paraquat on the human nervous and immune systems has become evident.

Incendiaries. Incendiaries are chemicals that cause fires. In warfare, they are also to remove vegetation. An infamous incendiary is napalm. Napalm is a mixture of naphthenic acid, coconut fatty acids, and palm oil. In addition to its highly flammable property, napalm absorbs into exposed skin, where it can cause severe burns if ignited. Napalm was used as an offensive weapon by the United States during the Vietnam War.

Modern Day Chemical Warfare

In 2003, the use of chemical weapons remains a threat from rogue states and terrorists. Current world attention is focused on the former chemical warfare capabilities of Iraq. It is known that Iraq engaged in chemical warfare research and weaponization in the 1980s and 1990s, and as of early 2003, before the U.S. war in Iraq, had not fully complied with United Nations resolutions requiring disclosure and destruction of their chemical weapons program.


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

Technology

**Chemical warfare technology timeline**
	Agents	Dissemination	Protection	Detection
1900s	Chlorine Chloropicrin Phosgene Mustard gas	Wind dispersal		Smell
1910s	Lewisite	Chemical shells	Gas mask Rosin oil clothing
1920s		Projectiles w/ central bursters	CC-2 clothing
1930s	G-series nerve agents	Aircraft bombs		Blister agent detectors Color change paper
1940s		Missile warheads Spray tanks	Protective ointment (mustard) Collective protection Gas mask w/ Whetlerite
1950s
1960s	V-series nerve agents	Aerodynamic	Gas mask w/ water supply	Nerve gas alarm
1970s
1980s		Binary munitions	Improved gas masks (protection, fit, comfort)	Laser detection
1990s	Novichok nerve agents

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.

Chemical weapon agents

See also: List of chemical weapon agents

A chemical used in warfare is called a chemical weapon agent (CWA). About 70 different chemicals have been used or stockpiled as chemical weapon 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 weapon 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 weapon 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.

Persistency

All chemical weapon agents are classified 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.

Classes

Chemical weapon 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 weapon agents are as follows:

**Classes of chemical weapon agents**
Class of agent	Agent Names	Mode of Action	Signs and Symptoms	Rate of action	Persistency
Nerve	Cyclosarin (GF) Sarin (GB) Soman (GD) Tabun (GA) VX Some insecticides Novichok agents	Inactivates enzyme acetylcholinesterase, preventing the breakdown of the neurotransmitter acetylcholine in the victim's synapses and causing both muscarinic and nicotinic effects	Miosis (pinpoint pupils) Blurred/dim vision Headache Nausea, vomiting, diarrhea Copious secretions/sweating Muscle twitching/fasciculations Dyspnea Seizures Loss of consciousness	Vapors: seconds to minutes; Skin: 2 to 18 hours	VX is persistent and a contact hazard; other agents are non-persistent and present mostly inhalation hazards.
Asphyxiant/Blood	Most Arsines Cyanogen chloride Hydrogen cyanide	Arsine: Causes intravascular hemolysis that may lead to renal failure. Cyanogen chloride/hydrogen cyanide: Cyanide directly prevents cells from utilizing oxygen. The cells then uses anaerobic respiration, creating excess lactic acid and metabolic acidosis.	Possible cherry-red skin Possible cyanosis Confusion Nausea Patients may gasp for air Seizures prior to death Metabolic acidosis	Immediate onset	Non-persistent and an inhalation hazard.
Vesicant/Blister	Sulfur mustard (HD, H) Nitrogen mustard (HN-1, HN-2, HN-3) Lewisite (L) Phosgene oxime (CX)	Agents are acid-forming compounds that damages skin and respiratory system, resulting burns and respiratory problems.	Severe skin, eye and mucosal pain and irritation Skin erythema with large fluid blisters that heal slowly and may become infected Tearing, conjunctivitis, corneal damage Mild respiratory distress to marked airway damage	Mustards: Vapors: 4 to 6 hours, eyes and lungs affected more rapidly; Skin: 2 to 48 hours Lewisite: Immediate	Persistent and a contact hazard.
Choking/Pulmonary	Chlorine Hydrogen chloride Nitrogen oxides Phosgene	Similar mechanism to blister agents in that the compounds are acids or acid-forming, but action is more pronounced in respiratory system, flooding it and resulting in suffocation; survivors often suffer chronic breathing problems.	Airway irritation Eye and skin irritation Dyspnea, cough Sore throat Chest tightness Wheezing Bronchospasm	Immediate to 3 hours	Non-persistent and an inhalation hazard.
Lachrymatory agent	Tear gas Pepper spray	Causes severe stinging of the eyes and temporary blindness.	Powerful eye irritation	Immediate	Non-persistent and an inhalation hazard.
Incapacitating	Agent 15 (BZ)	Causes atropine-like inhibition of acetylcholine in subject. Causes peripheral nervous system effects that are the opposite of those seen in nerve agent poisoning.	May appear as mass drug intoxication with erratic behaviors, shared realistic and distinct hallucinations, disrobing and confusion Hyperthermia Ataxia (lack of coordination) Mydriasis (dilated pupils) Dry mouth and skin	Inhaled: 30 minutes to 20 hours; Skin: Up to 36 hours after skin exposure to BZ. Duration is typically 72 to 96 hours.	Extremely persistent in soil and water and on most surfaces; contact hazard.
Cytotoxic proteins	Non-living biological proteins, such as: Ricin Abrin	Inhibit protein synthesis	Latent period of 4-8 hours, followed by flu-like signs and symptoms Progress within 18-24 hours to: Inhalation: nausea, cough, dyspnea, pulmonary edema Ingestion: Gastrointestinal hemorrhage with emesis and bloody diarrhea; eventual liver and kidney failure.	4-24 hours; see symptoms. Exposure by inhalation or injection causes more pronounced signs and symptoms than exposure by ingestion	Slight; agents degrade quickly in environment

There are other chemicals used militarily that are not technically considered to be "chemical weapon agents," such as:

Defoliants that destroy vegetation, but are not immediately toxic to human beings. (Agent Orange, for instance, used by the United States in Vietnam, contained dioxins and is known for its 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.

Designations

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 weapon 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:

Blood agents:	Vesicants:
Cyanogen chloride: CK Hydrogen cyanide: AC	Lewisite: L Sulfur mustard: H, HD, HS, HT
Pulmonary agents:	Incapacitating agents:
Phosgene: CG	Quinuclidinyl benzilate: BZ
Lachrymatory agents:	Nerve agents:
Pepper spray: OC Tear gas: CN, CS, CR	Sarin: GB VE, VG, VM, VX

Delivery

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

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.

Thermal dissemination

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

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 weapon agent of a predetermined particle size can predictably and reliably hit a target.

Protection against chemical warfare

Sociopolitical climate

ARMIS BELLA NON VENENIS GERI
"War is fought with weapons, not with poisons"

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."

Efforts to eradicate chemical weapons

Nation	CW Possession	Signed CWC	Ratified CWC
Albania	Known	January 14 1993	May 11 1994
China	Probable	January 13 1993	April 4 1997
Egypt	Probable	No	No
France	Probable	January 13 1993	March 2 1995
India	Known	January 14 1993	September 3 1996
Iran	Known	January 13 1993	November 3 1997
Israel	Probable	January 13 1993	No
Libya	Known	No	January 6 2004 (acceded)
Myanmar (Burma)	Possible	January 13 1993	No
North Korea	Known	No	No
Pakistan	Probable	January 13 1993	October 28 1997
Russia	Known	January 13 1993	November 5 1997
Serbia and Montenegro	Probable	No	April 20 2000 (acceded)
Sudan	Possible	No	May 24 1999 (acceded)
Syria	Known	No	No
Taiwan	Possible	n/a	n/a
United States	Known	January 13 1993	April 25 1997
Vietnam	Probable