The use and possession of chemical weapons is prohibited under international law. However, several nations continue to maintain active chemical weapons programs, despite a prevailing norm against the use of chemical weapons and international efforts to destroy existing stockpiles.
The following are basic answers to frequently asked questions regarding the different types of chemical weapons and delivery systems, the history of chemical weapons use, international legal regimes that seek to curb the use and stockpiling of chemical weapons, and current efforts to verifiably destroy chemical weapons arsenals.
I. What are chemical weapons?
II. How are chemical weapons delivered?
III. When have chemical weapons been used?
IV. Are chemical weapons prohibited?
V. Who has chemical weapons?
VI. How are chemical weapons destroyed?
A chemical weapon is any toxic chemical that can cause death, injury, incapacitation, and sensory irritation, deployed via a delivery system, such as an artillery shell, rocket, or ballistic missile. Chemical weapons are considered weapons of mass destruction and their use in armed conflict is a violation of international law.
Primary forms of chemical weapons include nerve agents, blister agents, choking agents, and blood agents. These agents are categorized based on how they affect the human body.
Nerve agents. Generally considered the most deadly of the different categories of chemical weapons, nerve agents – in liquid or gas form - can be inhaled or absorbed through the skin. Nerve agents inhibit the body’s respiratory and cardiovascular capability by causing severe damage to the central nervous system, and can result in death. The most common nerve agents include Sarin, Soman, and VX.
Blister agents. Blister agents can come in forms of gas, aerosol, or liquid and cause severe burns and blistering of the skin. They can also cause complications to the respiratory system if inhaled and digestive tract if ingested. Common forms of blister agents include Sulfur Mustard, Nitrogen Mustard, Lewisite and Phosgene Oximine.
Choking agents. Choking agents are chemical toxins that directly attack the body’s respiratory system when inhaled and cause respiratory failure. Common forms of choking agents include phosgene, chlorine, and chloropicrin.
Blood agents. Blood agents interfere with the body’s ability to use and transfer oxygen through the blood stream. Blood agents are generally inhaled and then absorbed into the blood stream. Common forms of blood agents include Hydrogen Chloride and Cyanogen Chloride.
Riot control agents, such as tear gas, are considered chemical weapons if used during war. States can legitimately possess riot control agents and use them for law enforcement purposes, but states that are members of the Chemical Weapons Convention must declare what type of riot agents they possess.
A chemical weapon attack occurs in two phases: delivery and dissemination. The delivery phase refers to the launching of the rocket, bomb, or artillery shell. The dissemination phase involves the dispersal of the chemical agent from the weapon.
Chemical weapons can be delivered via a variety of mechanisms including but not limited to; ballistic missiles, air dropped gravity bombs, rockets, artillery shells, aerosol canisters, and mortars.
Artillery shells are conventional shells that have been converted to disperse chemical weapons. The most traditional delivery vehicle of chemical agents, dispersion occurs through an explosive charge that expels the chemical agent laterally.
Air delivered systems can be deployed via gravity bombs, spray tank, or rockets. Ground detonated and airburst gravity bombs are generally delivered through fixed wing aircraft, while helicopters have been traditionally deployed with spray tanks and rockets.
Ballistic missiles carrying chemical weapons – via a fill tank or sub munitions - utilize an airburst to disperse chemical agents over a broad area. The use of sub munitions increases the area in which chemical agents can be dispersed. Compared to other delivery systems, ballistic missiles expand the range of targets that combatants can target with chemical weapons. However, the use of explosives to disperse the chemical agent reduces the potency of the weapon in combat situations.
Cruise missiles. Unlike ballistic missiles, which utilize explosives to discharge the agent, cruise missiles can disperse chemical agents in a gradual and controlled fashion.
Unmanned Aerial Vehicles or UAVs are another platform that combatants may utilize to disperse chemical agents. Like cruise missiles, UAVs are ideal platforms for slower dissemination due to controllable speeds, and dispersal over a wide area. UAVs can fly below radar detection and change directions, allowing them to be retargeted during flight.
Dissemination is the most critical phase of a chemical weapon and generally determines its effectiveness. Generally, dissemination has been done via explosives that expel the agent laterally. Other forms of dissemination include aerodynamic dissemination, a non-explosive delivery mechanism that deploys the chemical agent through dispersion lines.
The use of harmful chemicals in warfare, personal attacks, and assassinations dates back centuries, but the rise of industrial production of chemicals in the late 19th century opened the door to more massive use of chemical agents in combat. The first major use of chemicals on the battlefield was in World War I when Germany released chlorine gas from pressurized cylinders in April 1915 at Ypres, Belgium. Ironically, this attack did not technically violate the 1899 Hague Peace Conference Declaration, the first international attempt to limit chemical agents in warfare, which banned only “the use of projectiles the sole object of which is the diffusion of asphyxiating or deleterious gases.” Historians estimate that, with the introduction of mustard gases in 1917, chemical weapons and agents injured some one million soldiers and killed 100,000 during the 1914-1918 war.
The 1925 Geneva Protocol sought to ban the use of biological and chemical weapons, but many of its signers joined with major reservations. China, France, the Soviet Union, and the United Kingdom all joined in the 1920s, but Japan did not join until 1970 and the United States until 1975. Between the two world wars, there were a number of reports of use of chemical weapons in regional conflicts: Morocco in 1923-1926, Tripolitania (Libya) in 1930, Sinkiang (China) in 1934, Abyssinia (Ethiopia) in 1935-1940, and Manchuria (China) in 1937-1942. World War II saw no major use of chemical weapons, with the exception of the Sino-Japanese conflict, and both President Franklin Roosevelt and German leader Adolf Hitler had stated publicly that they were personally against the first use of chemical weapons.
Most of the major powers in World War II developed, produced, and stockpiled large amounts of chemical weapons during the war. Since the end of the war in 1945, there have been only sporadic reports of limited use of chemical weapons, including in the Yemen war of 1963-1967 when Egypt bombed Yemeni villages, killing some 1,500 people. The United States heavily used herbicides such as Agent Orange and tear gas in the Vietnam War in the 1960s; although such chemicals are not covered under the Chemical Weapons Convention (CWC), some observers saw this as chemical warfare. Iraq used chemical weapons in the 1980-1988 Iran-Iraq war and against the Kurds in Halabja in 1988. These two cases provoked widespread public opposition to the horrors and indiscriminate nature of deadly chemical agents and certainly helped advance CWC negotiations, which had begun in the early 1980s, to their conclusion in 1992.
The use of the nerve agent sarin by the Japanese terrorist group Aum Shinrikyo in June 1994 in Matsumoto, Japan, and again on March 20, 1995, in the Tokyo subway system, killing 19 people and injuring some 5,000, suddenly brought to light the potential threat of nonstate actors intent on using weapons of mass destruction. The first official on-site inspection by the United States of a Russian chemical weapons stockpile in the Kurgan Oblast along the border of Kazakhstan in July 1994 illustrated that Russian chemical weapons arsenals left much to be desired regarding security against theft, diversion, and terrorism.
Iraqi insurgents in recent years have combined tanks of chlorine gas with improvised explosive devices, but with little success. There have been more recent reports of the possible limited use of chemical agents by Taliban insurgents in Afghanistan and by Turkish troops against Kurdish rebels in eastern Turkey, but these allegations remain unproven. In public statements, Osama bin Laden and al Qaeda have repeatedly threatened to use nuclear, chemical, biological, and radiological weapons.
In July 2012, the Syrian government publically acknowledged the existence of its chemical stockpile for the first time. Syria is believed to possess hundreds of tons of mustard gas, blister agents, and nerve agents, which could include sarin and the agent VX. Intelligence reports by the United States, the United Kingdom, and France assess that the Assad regime used chemical weapons against opposition forces on several occasions in 2013, including an attack in Damascus that killed over 1,400 people. The United Nations, in cooperation with the OPCW, is also investigating the use of chemical weapons in Syria.
On September 14, after two days of meetings, U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov reached an agreement on a detailed plan for the accounting, inspection, control, and elimination of Syria’s chemical weapons. The plan requires Syria to provide a full declaration of its stockpile “within a week” and provide the OPCW and the UN access to all chemical weapons sites in Syria. The plan calls for the OPCW inspectors to complete their initial inspections by November and calls for the destruction of the stockpile of chemical weapons and chemical agents by the first half of 2014. The United States and Russia will now seek to secure approval of the plan by the OPCW executive council and then a UN Security Council resolution. The agreement outlined states that “in the event of non-compliance, including unauthorized transfer, or any use of chemical weapons by anyone in Syria, the UN Security Council should impose measures under Chapter VII of the UN Charter.
For more on the history of CW use, click here (from which much of the information in this section was drawn.)
Yes. The horrendous and widespread use of chemical weapons in World War I prompted international efforts to curb the use and production of chemical agents.
The two major protocols that target chemical weapons are the 1925 Geneva Protocol and the Chemical Weapons Convention (CWC). The former provides the initial international legal framework for controls on the use of chemical weapons, while the latter establishes comprehensive international standards that eliminated both the production and use of chemical weapons for most major actors.
1925 Geneva Protocol: Signed in 1925, the Geneva Protocol was drafted and signed at the Conference for the Supervision of the International Trade in Arms and Ammunition, and prohibits the use of chemical and biological weapons in the field of conflict. While it prohibits the use of chemical weapons, the Geneva Protocol does not regulate the production, research or stockpiling of these weapons. It allows nations to reserve the right to retaliate with chemical weapons should it be subject to an adversarial chemical attack. It also does not regulate the use of chemical weapons for internal conflicts. However, over time, through customary international law, it is widely considered applicable to these conflicts as well. Interest in verifiable elimination of existing stockpiles of chemical weapons fueled the push for the more robust CWC in 1993.
Chemical Weapons Convention: The CWC is a multilateral treaty that completely bans the use and possession of chemical weapons. Established on Jan. 13, 1993, the CWC entered into force in Aug. 29, 1997 and has 189 members. Currently two nations – Israel and Myanmar – have acceded but not ratified the treaty, while four nations (Angola, Egypt, North Korea, and South Sudan) have neither signed nor acceded to the CWC. Syria sent a letter to the UN Secretary General on September 12, 2013, indicating that it acceeded to the treaty after pressure from the international community and threats of a U.S. miltiary strike after the Assad regime was found to have used chemical weapons on multiple occasions in 2013. When Syria's accession is complete, it will be the 190th country party to the treaty.
The CWC establishes comprehensive protocols that ban the use, production, preparation for military use, dissemination to other nations and storage of chemical agents and their delivery vehicles. The CWC requires universal adherence to its protocols, and establishes verification regimes that assure the destruction of member nation’s chemical weapon stockpiles. The CWC requires member nations to declare all chemical weapons sites and be subject to on-site inspection to ensure compliance. Verification is implemented through the Organization for the Prohibition of Chemical Weapons (OPCW) and involves routine on-site inspections and reporting. The CWC also promotes multilateral cooperation on peaceful chemical projects.
The Chemical Weapons Convention bans the development, production, acquisition, stockpiling, transfer, and use of chemical weapons and requires all possessor states to destroy their stockpiles safely. Article IV obligates each country to declare “all chemical weapons owned or possessed by a State Party, or that are located in any place under its jurisdiction or control” and to “destroy all chemical weapons.… Such destruction shall begin not later than two years after this Convention enters into force for it and shall finish not later than 10 years after entry into force of this Convention,” that is, by April 29, 2007. The treaty allows a deadline extension of up to five years from that date. The convention also requires round-the-clock, on-site inspection of all chemical weapons destruction operations and allows for challenge inspections of suspect activities. Seven countries declared chemical weapons stockpiles when they joined the CWC: Albania, India, Iraq, Libya, South Korea, the United States and Russia. Of those seven countries, Albania, South Korea, and India have completed destruction.
When Russia, the United States, and Libya declared that they would be unable to meet that deadline in 2012, CWC state parties agreed to extend the deadlines with increased reporting and transparency. Iraq’s chemical weapons are largely concentrated in debris in two bunkers bombed in the 1991 Persian Gulf War, and their contents remain somewhat unknown.
Russia declared the largest stockpile with 40,000 metric tons at seven arsenals in six regions of Russia. The United States declared 28,577 metric tons at nine stockpiles in eight states and on Johnston Atoll west of Hawaii. Albania and Libya declared the smallest stockpiles, with 16 and 23 metric tons respectively. India and South Korea declared stockpiles in the 2,000-metric-ton range, maintaining a high degree of secrecy around the size, location, and composition of their weapons.
According to U.S. intelligence assessments, two non-parties to the CWC, Syria and North Korea, were long-suspected of possessing chemical weapons programs and stockpiles of agents. Syria admitted that it had chemical weapons in July 2012 and joined the CWC on September 12, 2013, but it remains unclear if it will follow through on its obligations under the treaty to declare and begin dismantlement of its program.
For more information, see here.
The United States: The United States began construction of its first prototype incinerator on Johnston Atoll in the 1980s. In 1990, it began burning 1,842 metric tons of chemical weapons, which had been secretly shipped from forward deployment in Germany and Okinawa many years earlier. When the CWC entered into force in 1997, the United States was already operating its first two incinerators on Johnston Atoll and in Tooele, Utah, which was the largest U.S. chemical weapons stockpile with 12,353 metric tons. The U.S. Army burned 1,436 metric tons, about 5 percent of the total chemical stockpile, at the two sites before the April 1997 entry into force.
The U.S. Army initially planned to construct three centralized incinerators to destroy the U.S. chemical weapons stockpile, and early schedules optimistically showed the United States completing operations in 1994. Congress subsequently banned transportation of chemical munitions on safety and security grounds, necessitating the current plan for a destruction facility at each of the nine U.S. sites at which chemical weapons are stored.
When the U.S. Senate finally approved the CWC, on April 25, 1997, after a long and contentious debate, the articles of ratification specified, among many other conditions, that the president place the highest priority on protection of public health and the environment and that the Army undertake the development and demonstration of nonincineration technologies for chemical weapons destruction.
Today the United States has constructed and operated five large incinerators: on Johnston Atoll and in Tooele, Utah, as previously noted; in Umatilla, Oregon; in Anniston, Alabama; and in Pine Bluff, Arkansas. The Johnston Atoll incinerator finished operations in 2000; the other four continue to operate. In addition, neutralization facilities were built in Newport, Indiana, and Edgewood, Maryland; they chemically treated and destroyed bulk VX nerve agent and mustard agent. The remaining two chemical weapons stockpiles in Pueblo, Colorado, and Blue Grass, Kentucky, will each be destroyed by chemical neutralization. Facilities to perform that task are under construction.
As of August 2013, the United States had destroyed approximately 90 percent of the chemical weapons stockpile it had declared as the CWC entered into force; nearly 25,000 metric tons of the declared total of 27,770.
The U.S. Army projects 2023 as the new likely end point.
Russia: Russian officials made it clear in 1997, when they signed and ratified the CWC, that they would need technical and financial support from other CWC members to meet its treaty deadlines. During the 1994 U.S. visit to Russia, Russian military officials and the chairman of the Duma defense committee rejected a U.S. offer made by the assistant to the secretary of defense for nuclear, chemical, and biological defense programs to construct an incinerator at the Shchuch’ye chemical weapons stockpile. Russian officials wanted to determine their own technologies for demilitarization and were very wary of incineration as too complex, too expensive, too dangerous, and too politically contentious.
The first Russian chemical weapons demilitarization facility, built and funded as a prototype facility by Germany for neutralizing lewisite, an older, arsenic-based chemical agent, opened in 2002 at Gorny in the Saratov Oblast. Since then, Russia has been able to open several more destruction facilities.
Most of these facilities have been supported financially by the Global Partnership Against the Spread of Weapons and Materials of Mass Destruction, founded by the Group of Eight at its summit meeting in Kananaskis, Canada, in 2002. As of 2010, the United States through the Cooperative Threat Reduction (CTR or Nunn-Lugar) program committed more than $1 billion since the mid-1990s to the planning and construction of the neutralization facility at Shchuch’ye, while Germany has committed $475 million (340 million euros) to construction at Gorny, Kambarka, and Pochep. Canada and the United Kingdom have contributed some $82 million and $39 million, respectively, while at least another 10 additional countries have contributed some $25 million.
As of August 2013, Russia had destroyed nearly 30,400 metric tons of its declared total of almost 40,000 metric tons of chemical weapons.
Russia has projected its operations will finish by the end of 2015, although some observers believe they may extend to 2016 or 2017.
Libya joined the CWC in 2004 and, in its submittal at the time, declared 25 metric tons of mustard agent in bulk containers. In addition, it declared one inactivated chemical weapons production facility, two chemical weapons storage sites, 1,300 metric tons of precursor chemicals, and 3,563 unfilled aerial bombs. It first planned on eliminating its chemical agent stockpile by the 2007 deadline. However, after aborted attempts at U.S. and Italian partnerships in its demilitarization program, it asked for several OPCW deadline extensions. Destruction of the stockpile was halted in February 2011 due to the armed uprising that resulted in the overthrow of the Gaddafi regime. At that time, 11.5 metric tons of chemical weapons remained in Libya’s declared stockpiles. During the uprising, additional, undeclared stockpiles of chemical weapons were found in the country. In May 2012 Libya set a target date of December 2013 for completing the destruction. As of August 2013, Libya had destroyed 22.3 metric tons of its total stockpile of 26.3 metric tons.
The last CWC state-party to declare a chemical weapons stockpile is Iraq. Iraq joined the CWC in early 2009 and declared two large, sealed bunkers with chemical weapons and related equipment and debris from the 1991 Persian Gulf War. Because at least one of these bunkers had been hit by aerial bombs in the war, there is no final inventory of weapons and agents, nor a thorough evaluation of the possible risks of open agents or unexploded ordnance in the bunkers. No decision has been made concerning the final disposition of these bunkers, but there is ongoing discussion at the OPCW with Iraqi officials about methods to evaluate the bunkers, possible costs of destruction, and options for further sealing the bunkers and improving local security.
Albania was the first possessor state to destroy its stockpile. Although it joined the CWC in 1994, it did not acknowledge its possession of 16 metric tons of mustard agent (as well as small quantities of lewisite and other chemicals) until 2003. The OPCW declared Albania’s destruction complete in July 2007. And additional cache was discovered in 2010 that Albania immediately reported to the OPCW. With U.S. assistance, destruction of that stockpile was completed in 2012.
India and South Korea joined the CWC in 1996 and 1997, respectively, and both declared chemical weapons stockpiles. Little is known publicly about either stockpile, but both countries successfully completed their destruction programs according to schedules extended beyond 2007 and approved by the OPCW—South Korea in 2008 and India in 2009.
South Korea refused to acknowledge its stockpile in any public presentations, including the annual speeches by its ambassador to the OPCW, and has claimed full confidentiality (“highly protected information”) under the Confidentiality Annex of the CWC; all OPCW delegations and staff therefore refer to it as “A State Party” in reference to possessor states.
India acknowledged its stockpile but has invoked confidentiality for the stockpile’s size, location, destruction technology, and agent types. India’s stockpile is generally thought to have consisted of mustard agent and to have been incinerated.
-Research Assistance by Eric Wey
 Types of Chemical Agent, Organization for the Prohibition of Chemical Weapons, Retrieved August 30, 2013, http://www.opcw.org/protection/types-of-chemical-agent/.
 Chemical Weapons Technology. (1998 ). In The Militarily Critical Technologies List Part II: Weapons of Mass Destruction Technologies; Department of Defense, Office of the Under Secretary of Defense for Acquisition and Technology. Retrieved August 28, 2013, from http://www.fas.org/irp/threat/mctl98-2/p2sec04.pdf.
 “Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare,” opened for signature on June 17, 1925, and entered into force on February 8, 1928.
 For the UN report on alleged use of chemical weapons by Iraq in 1984, see UN Security Council, “Report of the Specialists Appointed by the Secretary-General to Investigate Allegations by the Islamic Republic of Iran Concerning the Use of Chemical Weapons,” S/16433, March 26, 1984, http://www.iranwatch.org/international/UNSC/unsc-s16433-rptusecw-032684.pdf.
 Geneva Protocol (1925). Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare. Retrived August 29, 2013 from http://www.un.org/disarmament/WMD/Bio/pdf/Status_Protocol.pdf.
 Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction (Chemical Weapons Convention), Organization for the Prohibition of Chemical Weapons, Retrieved August 29, 2013.
 An example of this repeated usage of “A State Party” to represent South Korea as a chemical weapons possessor state is Ambassador Rogelio Pfirter’s statement before the OPCW Executive Council in 2009: “As of 30 September 2009, the aggregate amount of Category I chemical weapons destroyed by A State Party, Albania, India, the Russian Federation, and the United States of America was approximately 35,892 metric tonnes (MTs), or approximately 51.70% of the declared quantity of this category of chemical weapons. A State Party, Albania, and India had completed the destruction of all their Category I chemical weapons, while the Libyan Arab Jamahiriya has yet to commence destroying the Category I chemical weapons it had declared.” OPCW, “Note by the Director General,” EC-58/DG.11, October 7, 2009, p. 2.