|This article forms part of the series
|Cyanogen chloride (CK)|
|Hydrogen cyanide (AC)|
|Sulfur mustard gas (HD, H, HT, HL, HQ)|
|Nitrogen mustard gas (HN1, HN2, HN3)|
|Tabun (GA), Sarin (GB)
Soman (GD), Cyclosarin (GF)
|EA-3148, VE, VG, VM, VR, VX|
|Agent 15 (BZ)|
|Riot control agents|
|Pepper spray (OC)|
|CN gas (mace)|
|List of treaties|
This type of warfare is distinct from the use of conventional weapons or nuclear bombs because the destructive effects of chemical weapons are not primarily due to their explosive force. With proper protective equipment and contamination control, chemical weapons are of limited strategic use, due to their modern ineffectiveness. Chemical contamination will generally dissipate to safe levels within 48 to 72 hours.
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 biological warfare rather than chemical warfare; however, the use of nonliving toxic products produced by living organisms (e.g. toxins such as botulinum toxin, ricin, and 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 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 warfare agents during the 20th century.
Under the Convention, chemicals that are toxic enough to be used as chemical weapons, or that may be used to manufacture such chemicals, are divided into three groups according to their purpose and treatment:
|Wind dispersal||Gas masks, urinated-on gauze||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
|Protective ointment (mustard)
Gas mask w/ Whetlerite
|1960s||V-series nerve agents||Aerodynamic||Gas mask w/ water supply||Nerve gas alarm|
|1980s||Binary munitions||Improved gas masks
(protection, fit, comfort)
|1990s||Novichok nerve agents|
Initially, only well-known commercially available chemicals and their variants were used. These included chlorine and phosgene gas. The methods used to disperse these agents during battle were relatively unrefined and inefficient. Even so, casualties could be heavy, due to the mainly static troop positions which were characteristic features of trench warfare.
Germany, the first side to employ chemical warfare on the battlefield, 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.
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 employed mustard gas. 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.
Apart from the agent used, the delivery mode is very important. To achieve a nonpersistent deployment, the agent is dispersed into very small droplets comparable with the mist produced by an aerosol can. In this form not only the gaseous part of the agent (around 50%) but also the fine aerosol can be inhaled or taken up by the skin.
Modern doctrine requires very high concentrations almost instantly in order to be effective (one breath should contain a lethal dose of the agent). To achieve this, the primary weapons used would be rocket artillery or bombs and large ballistic missiles with cluster warheads. The contamination in the target area is only low or not existent and after four hours sarin or similar agents are not detectable anymore.
By contrast, persistent agents tend to remain in the environment for as long as several weeks, 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.
The droplet size used for persistent delivery goes up to 1 mm increasing the falling speed and therefore about 80% of the deployed agent reaches the ground, resulting in heavy contamination. This implies, that persistent deployment does not aim at annihilating the enemy but to constrain him.
Possible targets include enemy flank positions (averting possible counter attacks), artillery regiments, commando posts or supply lines. Possible weapons to be used are wide spread, because the fast delivery of high amounts is not a critical factor.
A special form of persistent agents are thickened agents. These comprise a common agent mixed with thickeners to provide gelatinous, sticky agents. Primary targets for this kind of use include airfields, due to the increased persistency and difficulty of decontaminating affected areas.
Chemical weapons are inert agents that come in four categories: choking, blister, blood and nerve. The 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:
|Class of agent||Agent Names||Mode of Action||Signs and Symptoms||Rate of action||Persistency|
|Nerve||Inactivates enzyme acetylcholinesterase, preventing the breakdown of the neurotransmitter acetylcholine in the victim's synapses and causing both muscarinic and nicotinic effects||
||VX is persistent and a contact hazard; other agents are non-persistent and present mostly inhalation hazards.|
|Asphyxiant/Blood||Immediate onset||Non-persistent and an inhalation hazard.|
|Vesicant/Blister||Agents are acid-forming compounds that damages skin and respiratory system, resulting burns and respiratory problems.||
||Persistent and a contact hazard.|
|Choking/Pulmonary||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.||Immediate to 3 hours||Non-persistent and an inhalation hazard.|
|Lachrymatory agent||Causes severe stinging of the eyes and temporary blindness.||Powerful eye irritation||Immediate||Non-persistent and an inhalation hazard.|
||Causes atropine-like inhibition of acetylcholine in subject. Causes peripheral nervous system effects that are the opposite of those seen in nerve agent poisoning.||
||Extremely persistent in soil and water and on most surfaces; contact hazard.|
Non-living biological proteins, such as:
|Inhibit protein synthesis||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 scheduled by the Chemical Weapons Convention, and thus are not controlled under the CWC treaties. These include:
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:
|Pulmonary agents:||Incapacitating agents:|
|Lachrymatory agents:||Nerve agents:|
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 is placing the chemical agent upon or adjacent to a target immediately before dissemination, so that the material is most efficiently used. Dispersion is the simplest technique of delivering an agent to its target. The most common techniques are munitions, bombs, projectiles, spray tanks and warheads.
World War I saw the earliest implementation of this technique. The actual first chemical ammunition was the French 26 mm cartouche suffocante rifle grenade, fired from a flare carbine. It contained 35g of the tear-producer ethylbromacetate, and was used in autumn 1914 – with little effect on the Germans.
The Germans on the other hand tried to increase the effect of 10.5 cm shrapnel shells by adding an irritant – dianisidine chlorosulphonate. Its use went unnoticed by the British when it was used against them at Neuve Chapelle in October 1914. Hans Tappen, a chemist in the Heavy Artillery Department of the War Ministry, suggested to his brother, the Chief of the Operations Branch at German General Headquarters, the use of the tear-gases benzyl bromide or xylyl bromide.
Shells were tested successfully at the Wahn artillery range near Cologne on 9 January 1915, and an order was placed for 15 cm howitzer shells, designated ‘T-shells’ after Tappen. A shortage of shells limited the first use against the Russians at Bolimów on 31 January 1915; the liquid failed to vaporize in the cold weather, and again the experiment went unnoticed by the Allies.
The first effective use were when the German forces at the Second Battle of 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. This made the gas doubly effective, as, in addition to damaging the enemy physically, it also had a psychological effect on the intended victims.
Another disadvantage was that 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 and cluster bombs 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 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.
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.
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 equipment (TECHINT); communications intercepts (COMINT); and detection of chemical manufacturing and chemical agents themselves (MASINT).
If all the preventive measures fail and there is a clear and present danger, then there is a need for detection of chemical attacks, collective protection, 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.
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.
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.
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 buildings exposed to persistent agents, such as blister agents, VX or other agents made persistent by mixing with a thickener, special equipment and materials might be needed. Some type of neutralizing agent will be needed; e.g. in the form of a spraying device with neutralizing agents such as Chlorine, Fichlor, strong alkaline solutions or enzymes . In other cases, a specific chemical decontaminant will be required.
The study of chemicals and their military uses was widespread in China and India. The use of toxic materials has historically been viewed with mixed emotions and moral qualms in the West. The practical and ethical problems surrounding poison warfare appeared in ancient Greek myths about Hercules' invention of poison arrows and Odysseus's use of toxic projectiles. There are many instances of the use of chemical weapons in battles documented in Greek and Roman historical texts; the earliest example was the deliberate poisoning of Kirrha's water supply with hellebore in the First Sacred War, Greece, about 590 BC.
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." Yet the Romans themselves resorted to poisoning wells of besieged cities in Anatolia in the second century B.C.E.
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."
|Nation||CW Possession||Signed CWC||Ratified CWC|
|Albania||Known||January 14, 1993||May 11, 1994|
|Burma (Myanmar)||Possible||January 13, 1993||No|
|the People's Republic of China||Probable||January 13, 1993||April 4, 1997|
|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|
|Japan||Probable||January 13, 1993||September 15, 1995|
|Libya||Known||No||January 6, 2004
|Pakistan||Probable||January 13, 1993||October 28, 1997|
|Russia||Known||January 13, 1993||November 5, 1997|
|Probable||No||April 20, 2000
|Sudan||Possible||No||May 24, 1999
|United States||Known||January 13, 1993||April 25, 1997|
|Vietnam||Probable||January 13, 1993||September 30, 1998|
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 United States and Russia.
Former US Vice President Dick Cheney opposed the signing ratification of a treaty banning the use chemical weapons, a recently unearthed letter shows. In a letter dated April 8, 1997, then Halliburton-CEO Cheney told Sen. Jesse Helms, the chairman of the Senate Foreign Relations Committee, that it would be a mistake for America to join the Convention. "Those nations most likely to comply with the Chemical Weapons Convention are not likely to ever constitute a military threat to the United States. The governments we should be concerned about are likely to cheat on the CWC, even if they do participate," reads the letter, published by the Federation of American Scientists.
The CWC was ratified by the Senate that same month. Since then, Albania, Libya, Russia, the United States, and India have declared over 71,000 metric tons of chemical weapon stockpiles, and destroyed about a third of them. Under the terms of the agreement, the United States and Russia are supposed to eliminate the rest of their supplies of chemical weapons by 2012. But that looks unlikely– the U.S. government estimates remaining stocks will be destroyed by 2017.
Chemical weapons have been used for millennia in the form of poisoned spears and 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.
Ancient Greek myths about Hercules poisoning his arrows with the venom of the Hydra Monster are the earliest references to toxic weapons in western literature. Homer's epics, the Iliad and the Odyssey, allude to poisoned arrows used by both sides in the legendary Trojan War (Bronze Age Greece).
The "Laws of Manu," a Hindu treatise on statecraft (ca 400 BC) forbids the use of poison and fire arrows, but advises poisoning food and water. Kautilya's "Arthashastra," a statecraft manual of the same era, contains hundreds of recipes for creating poison weapons, toxic smokes, and other chemical weapons. Ancient Greek historians recount that Alexander the Great encountered poison arrows and fire incendiaries in what is now Pakistan in the fourth century BC.
Sun Tzu's "Art of War" (ca 500 BC) advises the use of fire weapons. In 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 Kirrha.
Historian and philosopher David Hume, in his history of England, recounts how during early in the reign of Henry III (r.1216 - 1272) the English Navy destroyed an invading French fleet, by blinding the enemy fleet with "quicklime," the old name for calcium oxide. D’Albiney employed a stratagem against them, which is said to have contributed to the victory: Having gained the wind of the French, he came down upon them with violence; and throwing in their faces a great quantity of quicklime, which he purposely carried on board, he so blinded them, that they were disabled from defending themselves.
There is archaeological evidence that the Sasanians deployed chemical weapons against the Roman army in 3rd century AD/CE. Research carried out on the collapsed tunnels at Dura-Europos in Syria suggests that the Iranians used bitumen and sulphur crystals to get it burning. When ignited, the materials gave off dense clouds of choking gases which killed 20 Roman soldiers in the matter of 2 minutes.
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:
It is unknown whether this powder was ever actually used.
Earlier, in the 13th century, of Henry III the English Navy destroyed an invading French fleet, by blinding the enemy fleet with "quicklime," the old name for calcium oxide (see Calcium oxide). 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 Deadly Nightshade, 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:
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."
The Hague Declaration of 1899 and the Hague Convention of 1907 forbade the use of "poison or poisonous weapons" in warfare, yet more than 124,000 tons of gas were produced by the end of 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. 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 World War I-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 burns to anybody coming into contact with it.
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 Bolsheviks also employed poison gas in 1921 during the 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."
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. 150,000 chemical casualties were reported, mostly from mustard gas.
Despite article 171 of the Versailles Peace Treaty, article V of the Treaty in Relation to the Use of Submarines and Noxious Gases in Warfare  and a resolution adopted against Japan by the League of nations on 14 May 1938, the Imperial Japanese Army frequently used chemical weapons. Because of fear of retaliation however, those weapons were never used against Westerners, but against other Asians judged "inferior" by the imperial propaganda.
According to historians Yoshiaki Yoshimi and Kentaro Awaya, gas weapons, such as tear gas, were used only sporadically in 1937 but in the spring of 1938, however the Imperial Japanese Army began full-scale use of sneeze and nausea gas (red), and from summer 1939, mustard gas (yellow) was used against both Kuomintang and Communists Chinese troops.
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.
The Imperial Japanese Army used mustard gas and the recently-developed blister agent Lewisite against Chinese troops and guerrillas. Experiments involving chemical weapons were conducted on live prisoners (Unit 731 and Unit 516). The Japanese also carried chemical weapons as they swept through Southeast Asia towards Australia.
Some of these items were captured and analyzed by the Allies. Greatly concerned, Australia covertly imported 1,000,000 chemical weapons from the United Kingdom from 1942 onwards  .
Shortly after the end of World War I, Germany's General Staff enthusiastically pursued a recapture of their preeminent position in chemical warfare. In 1923, Hans von Seeckt pointed the way, by suggesting that German poison gas research move in the direction of delivery by aircraft in support of mobile warfare. Also in 1923, at the behest of the German army, poison gas expert Dr. Hugo Stolzenberg negotiated with the USSR to built a huge chemical weapons plant at Trotsk, on the Volga river.
Collaboration between Germany and the USSR in poison gas continued on and off through the 1920s. In 1924, German officers debated the use of poison gas versus non-lethal chemical weapons against civilians. Even before World War II, chemical warfare was revolutionized by Nazi Germany's discovery of the nerve agents tabun (in 1937) and sarin (in 1939) by Gerhard Schrader, a chemist of IG Farben.
IG Farben was Germany's premier poison gas manufacturer during World War I, so the weaponization of these agents can not be considered accidental. Both were turned over to the German Army Weapons Office prior to the outbreak of the war.
The nerve agent soman was later 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. The Nazis developed and manufactured large quantities of several agents, but chemical warfare was not extensively used by either side. 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. Fisk, Robert (December 30, 2000), "Poison gas from Germany", Independent, http://www.zmag.org/hussein.htm
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" out of 628 mustard gas military casualties. 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.
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 the state changed sides, and prisoner of war interrogations suggesting that preparations were being made to use a "new, egregiously potent gas" if the war turned decisively against Germany. Atkinson concludes that "No commander in 1943 could be cavalier about a manifest threat by Germany to use gas."
The first attack took place on June 8, 1963 against Kawma, a village of about 100 inhabitants in northern Yemen, killing about seven people and damaging the eyes and lungs of twenty-five others. This incident is considered to have been experimental, and the bombs were described as "home-made, amateurish and relatively ineffective". The Egyptian authorities suggested that the reported incidents were probably caused by napalm, not gas.
There were no reports of gas during 1964, and only a few were reported in 1965. The reports grew more frequent in late 1966. On December 11, 1966, fifteen gas bombs killed two people and injured thirty-five. On January 5, 1967, the biggest gas attack came against the village of Kitaf, causing 270 casualties, including 140 fatalities. The target may have been Prince Hassan bin Yahya, who had installed his headquarters nearby. The Egyptian government denied using poison gas, and alleged that Britain and the US were using the reports as psychological warfare against Egypt. On February 12, 1967, it said it would welcome a UN investigation. On March 1, U Thant said he was "powerless" to deal with the matter.
On May 10, the twin villages of Gahar and Gadafa in Wadi Hirran, where Prince Mohamed bin Mohsin was in command, were gas bombed, killing at least seventy-five. The Red Cross was alerted and on June 2, it issued a statement in Geneva expressing concern. The Institute of Forensic Medicine at the University of Berne made a statement, based on a Red Cross report, that the gas was likely to have been halogenous derivatives - phosgene, mustard gas, lewisite, chloride or cyanogen bromide.
The gas attacks stopped for three weeks after the Six-Day War of June, but resumed on July, against all parts of royalist Yemen. Casualty estimates vary, and an assumption, considered conservative, is that the mustard and phosgene-filled aerial bombs caused approximately 1,500 fatalities and 1,500 injuries.
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 war 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.
There is some evidence suggesting that Vietnamese troops used phosgene gas against Cambodian resistance forces in Thailand during the 1984-1985 dry-season offensive on the Thai-Cambodian border.
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.
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.
In 1961 and 62 the Kennedy administration authorized the use of chemicals to destroy vegetation and food crops in South Vietnam. Between 1961 and 1967 the US Air Force sprayed 12 million US gallons of concentrated herbicides, mainly Agent Orange (containing dioxin as an impurity in the manufacturing process) over 6 million acres (24,000 km²) of foliage and trees, affecting an estimated 13% of South Vietnam's land. In 1965, 42% of all herbicides were sprayed over food crops. Besides destroying vegetation used as cover by the NLF and destroying food crops the herbicide was used to drive civilians into RVN-controlled areas.
In 1997, an article published by the Wall Street Journal reported that up to half a million children were born with dioxin related deformities, and that the birth defects in South Vietnam were fourfold those in the North. The use of Agent Orange may have been contrary to international rules of war at the time. It is also of note that the most likely victims of such an assault would be small children. A 1967 study by the Agronomy Section of the Japanese Science Council concluded that 3.8 million acres (15,000 km²) of land had been destroyed, killing 1000 peasants and 13,000 livestock.
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.
In December, 2001, the United States Department of Health and Human Services, CDC, NIOSH, National Personal Protective Technology Laboratory (NPPTL), along with the U.S. Army Research, Development Engineering Command Edgewood Chemical/Biological Center (ECBC), and the U.S. Department of Commerce National Institute for Standards and Technology (NIST) published the first of six technical performance standards and test procedures designed to evaluate and certify respirators intended for use by civilian emergency responders to a chemical, biological, radiological, or nuclear weapon release, detonation, or terrorism incident. To date NIOSH/NPPTL has published six new respirator performance standards based on a tiered approach that relies on traditional industrial respirator certification policy, next generation emergency response respirator performance requirements, and special live chemical warfare agent testing requirements of the classes of respirators identified to offer respiratory protection against chemical, biological, radiological, and nuclear (CBRN) agent inhalation hazards. These CBRN respirators are commonly known as open-circuit self-contained breathing apparatus (CBRN SCBA), air-purifying respirator (CBRN APR), air-purifying escape respirator (CBRN APER), self-contained escape respirator (CBRN SCER) and loose or tight fitting powered air-purifying respirators (CBRN PAPR). Current NIOSH-approved/certified CBRN respirator concept standards and test procedures can be found at the webpage: http://www.cdc.gov/niosh/npptl/standardsdev/cbrn/
A 1994 United States Senate Report, entitled "Is military research hazardous to veterans health? Lessons spanning a half century," detailed the United States Department of Defense's practice of experimenting on animal and human subjects, often without their knowledge or consent. This included:
From 1962 to 1973, the Department of Defense planned 134 tests under Project 112, a chemical and biological weapons "vulnerability-testing program." In 2002, the Pentagon admitted for the first time that some of tests used real chemical and biological weapons, not just harmless stimulants.
Specifically under Project SHAD, 37 secret tests were conducted in California, Alaska, Florida, Hawaii, Maryland and Utah. Land tests in Alaska and Hawaii used artillery shells filled with sarin and VX gas, while Navy trials off the coasts of Florida, California and Hawaii tested the ability of ships and crew to perform under biological and chemical warfare, without the crew's knowledge. The code name for the sea tests was Project Shipboard Hazard and Defense -- "SHAD" for short.
In October 2002, the Senate Armed Forces Subcommittee on Personnel held hearings, as the controversial news broke that chemical agents had been tested on thousands of American military personnel. The hearings were chaired by Senator Max Cleland, former VA administrator and Vietnam War veteran. Ironically, at the same time the Bush Administration pressed the Senate to declare war on Iraq, falsely claiming Saddam Hussein was stockpiling those same weapons.
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 1994, after a major campaign by U.S. scientists on his behalf, Mirzayanov was released.
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.
According to Mirzayanov, the Soviets also developed weapons that were safer to handle, leading to the development of the 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"). Together with Lev Fedorov, he told the secret Novichok story exposed in the newspaper Moscow News.
Chemical weapons employed by Saddam Hussein killed and injured numerous Iranians, and even 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.
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 survivors, some 5,000 seek medical treatment regularly and about 1,000 are still hospitalized with severe, chronic conditions.
Iraq also targeted Iranian civilians with chemical weapons. Many thousands were killed in attacks on populations in villages and towns, as well as front-line hospitals. Many still suffer from the severe effects.
Despite the removal of Saddam and his regime by Coalition forces, there is deep resentment and anger in Iran that it was Western companies based in the Netherlands, West Germany, France, and the U.S. that helped Iraq develop its chemical weapons arsenal in the first place, and that the world did nothing to punish Iraq for its use of chemical weapons throughout the war.
Shortly before war ended in 1988, the Iraqi Kurdish village of Halabja was exposed to multiple chemical agents, killing about 5,000 of the town's 50,000 residents . After the incident, traces of mustard gas and the nerve agents sarin, tabun and VX were discovered.
During the Persian Gulf War in 1991, Coalition forces began a ground war in Iraq. Despite the fact that they did possess chemical weapons, Iraq did not use any chemical agents against coalition forces. The commander of the Allied Forces, Gen. H. Norman Schwarzkopf, suggested this may have been due to Iraqi fear of retaliation with nuclear weapons.
Technically, the reported employment of tear gas by Argentine forces during the 1982 invasion of the Falkland Islands constitutes chemical warfare. However, the tear gas grenades were employed as nonlethal weapons to avoid British casualties. The barrack buildings the weapons were used on proved to be deserted in any case. The British claim that more lethal, but legally-justifiable as they are not considered chemical weapons under the Chemical Weapons Convention, white phosphorus grenades were used.
For many terrorist organizations, chemical weapons might be considered an ideal choice for a mode of attack, if they are available: they are cheap, relatively accessible, and easy to transport. A skilled chemist can readily synthesize most chemical agents if the precursors are available.
The earliest successful use of chemical agents in a non-combat setting was in 1946, motivated by a desire to obtain revenge on Germans for the Holocaust. Three members of a Jewish group calling themselves Dahm Y'Israel Nokeam ("Avenging Israel's Blood") hid in a bakery in the Stalag 13 prison camp near Nuremberg, Germany, where several thousand SS troops were being detained. The three applied an arsenic-containing mixture to loaves of bread, sickening more than 2,000 prisoners, of whom more than 200 required hospitalization.
In July 1974, a group calling themselves the Aliens of America successfully firebombed the houses of a judge, two police commissioners, and one of the commissioner’s cars, burned down two apartment buildings, and bombed the Pan Am Terminal at Los Angeles International Airport, killing three people and injuring eight. The organization, which turned out to be a single resident alien named Muharem Kurbegovic, claimed to have developed and possessed a supply of sarin, as well as 4 unique nerve agents named AA1, AA2, AA3, and AA4S. Although no agents were found at the time he was arrested in August 1974, he had reportedly acquired "all but one" of the ingredients required to produce a nerve agent. A search of his apartment turned up a variety of materials, including precursors for phosgene and a drum containing 25 pounds of sodium cyanide.
The first successful use of chemical agents by terrorists against a general civilian population was on March 20, 1995. Aum Shinrikyo, an apocalyptic group based in Japan that believed it necessary to destroy the planet, released sarin into the Tokyo subway system killing 12 and injuring over 5,000. The group had attempted biological and chemical attacks on at least 10 prior occasions, but managed to affect only cult members. The group did manage to successfully release sarin outside an apartment building in Matsumoto in June 1994; this use was directed at a few specific individuals living in the building and was not an attack on the general population.
On 29 December 1999, four days after Russian forces began assault of Grozny, Chechen terrorists exploded two chlorine tanks in town. Because of the wind conditions, no Russian soldiers were injured.
In 2001, after carrying out the attacks in New York City on September 11, the organization Al Qaeda announced that they were attempting to acquire radiological, biological and chemical weapons. This threat was lent a great deal of credibility when a large archive of videotapes was obtained by the cable television network CNN in August 2002 showing, among other things, the killing of three dogs by an apparent nerve agent.
On October 26, 2002, Russian special forces used a chemical agent (presumably KOLOKOL-1, an aerosolized fentanyl derivative), as a precursor to an assault on Chechen terrorists, ending the Moscow theater hostage crisis. All 42 of the terrorists and 120 of the hostages were killed during the raid; all but one hostage, who was killed, died from the effects of the agent.
In early 2007 multiple terrorist bombings have been reported in Iraq using chlorine gas. These attacks have wounded or sickened more than 350 people. Reportedly the bombers are affiliated with Al-Qaeda in Iraq and have used bombs of various sizes up to chlorine tanker trucks. United Nations Secretary-General Ban Ki-moon condemned the attacks as, "clearly intended to cause panic and instability in the country."
Chemical warfare means using chemical compounds and agents in war to cause injury or death. The chemicals used are not explosive, but they are poisonous. The chemicals are also not made from living beings or organic matter (See Biological warfare). The main types of agents used in chemical warfare are:
If we use chemicals (like Agent Orange or glyphosate) to destroy plants, sometimes human beings may be affected by side-effects. But, we will not call it chemical warfare. Chemical warfare covers only direct attacks on human life.
The first form of chemical warfare was in the form of poisoned arrows, and spear-tips, during the Stone age. These were dipped in poison (like that from snakes or scorpions. Sometimes poisonous plants were used. The Ancient Chinese used various forms of poisonous smokes, when they besieged a city. Ancient Greeks used a form of burning wood, pitch, and sulphur.
Chemical warfare was used for the first time in World War I. Chlorine, mustard gas, and phosgene gas were used in the war, to kill or hurt enemy soldiers. But, they were not used very much in World War II, apart by the Japanese army during the invasion of China. This was because, everybody was afraid that the other side would use weapons like theirs. Also, chemical weapons were not easy to use. The time taken to use them, slowed the advance of one's own troops. The raw materials for producing chemical weapons were not easy to get. This was because World War II was fought in areas which were not connected well by railroads.
According to international law, it is wrong to use chemical weapons. There are many rules that ban the production, import and use of chemical weapons. Of these the most important is the Chemical Weapons Convention(CWC).
UN formed a working group in 1980 that works for making the number of chemical weapons in the world less. On April 4, 1984 the President of United States, Ronald Reagan called for a worldwide ban on chemical weapons. After this, negotiations between various countries started. The Chemical Weapons Convention was signed in 1993 and came into effect in 1997. Experts believe that 70,000 metric tons of chemical weapons are known to be present totally in this world. Out of this, 8000 metric tons have been destroyed in the past few years. By 2003, United States had destroyed 23% of its total chemical weapons. Other countries like India, South Korea and Russia are destroying chemical weapons under the CWC. Libya is also destroying its weapons in the last few years.