Chemical Warfare: History, Methods, and the Devastating Reality of the World's Cruelest Weapons

Among the arsenal of weapons humanity has devised, none carries quite the same visceral horror as chemical weapons. While nuclear warheads can annihilate tens of thousands in a single detonation and biological agents can spiral into global pandemics, chemical weapons occupy a uniquely cruel category — substances engineered with the sole purpose of attacking the human body, inflicting agonizing pain, and destroying warfighters from the inside out. Prohibited under multiple layers of international law including the Geneva Protocol, the Chemical Weapons Convention, and the Hague Conventions, these weapons of mass destruction remain disturbingly relevant in the modern era. From the chlorine-choked trenches of World War I to the gas chambers of the Holocaust, the history of chemical warfare is a chronicle of humanity’s capacity for calculated cruelty — and a stark reminder that the legal prohibitions meant to consign these weapons to history have never been fully effective.

What Defines a Chemical Weapon

By definition, a chemical weapon is any toxic chemical capable of causing death, injury, incapacitation, or sensory irritation when delivered into battle or otherwise deployed in a conflict. Critically, international law does not require a chemical weapon to be lethal to qualify as one. A toxin designed to blind an enemy force, scald their skin and lungs, overwhelm them with coughing fits, or render them unconscious all falls under the same legal and moral umbrella. Context matters as well: tear gas, for instance, is not classified as a chemical weapon when used for domestic law enforcement purposes, but the moment it is deployed over the course of a military conflict, it crosses the threshold into chemical weaponry.

What unifies all chemical weapons beyond their toxic composition is their fundamental purpose — they exist to attack the human body. Unlike conventional munitions designed to disable or destroy an adversary’s equipment and infrastructure, chemical weapons target warfighters and people directly. Their purpose is to use pain, suffering, and death as instruments of coercion, imposing a terrible cost on those who ordered troops into combat. This distinction is what places chemical weapons in the category of weapons of mass destruction and what has driven the international community’s repeated — if imperfectly enforced — efforts to ban them.

The Four Categories of Chemical Weapons

Chemical weapons fall into four basic categories, each with a uniquely ruinous effect on the human body: blood agents, blister agents, choking agents, and nerve agents.

Blood agents impede the body’s ability to distribute oxygen to its cells through the bloodstream, causing the body to shut down in minutes or even seconds. Typically colorless with only faint odors, blood agents can often be identified by the bright red blood of the victim after exposure. These agents are either cyanide-based or arsenic-based.

Blister agents cause chemical burns so severe that they produce excruciating water blisters across affected areas, with a high potential for infection. In cases of severe exposure, blister agents attack the insides of the lungs and destroy the respiratory system, while simultaneously causing blinding effects on the eyes. Mustard gas is the most infamous example of a blister agent.

Choking agents are designed to flood the respiratory system, cause a buildup of fluids in the lungs, and force a victim to choke to death. Often accompanied by severe corrosive burns, the most well-known choking agents — chlorine gas and phosgene — can kill with incredible pain.

Nerve agents represent the most lethal and efficient class of chemical weapon. They work by blocking signals from the brain to the body’s organs, causing convulsions, loss of control over bodily functions, and often chemical blistering and suffocation. Survivors are frequently impaired for life. This category includes sarin, VX, and Novichok, among others.

Some chemical weapons fall outside these four classifications, such as the cytotoxic protein ricin or incapacitating agents like sleeping gas, but the four main categories capture the bulk of the variation between chemical warfare agents.

Manufacturing and Delivery: Where Chemical Weapons Come From

In a technical sense, chemical weapons are compounds that must be manufactured. In most cases, they require component chemicals, specialized facilities, and expert personnel to create them, along with additional industrial support to eventually weaponize them. The origins of these substances vary considerably. Some chemical weapons can be adapted relatively easily from legitimate civilian programs — the choking agent phosgene, for example, is in widespread use in the manufacture of plastics.

Others, however, are rarely if ever used for anything other than war. VX and mustard gas are two prominent examples of agents with essentially no peaceful application.

The question of how chemical weapons reach the battlefield is equally important. The delivery mechanisms are diverse and adaptable: ballistic missiles, cruise missiles, rockets, smart or standard bombs, artillery shells, tank rounds, mortars, land mines, and sprayer devices can all deliver chemical weapons to a target. They typically release an aerosolized agent — a gas — capable of spreading over large areas.

Some delivery mechanisms are designed with specialized spreading features, such as a bomb engineered to disperse the chemical agent in all directions. Others involve simply releasing gas into the air and allowing wind and atmospheric conditions to do the rest.

Tactical and Strategic Value of Chemical Weapons

Despite the very sensible condemnation of chemical weapons under international law, they remain a tactical and strategic tool for nations or non-state actors willing to use them. It is partly because of how effective chemical weapons can be that monitoring and outlawing their use is so critically important.

Chemical weapons are a highly effective mechanism for killing enemy troops, rapidly depleting an adversary’s numbers and forcing both tactical and, in some cases, strategic changes to how an opponent approaches its war aims. When they are not lethal, they excel at incapacitating their victims — either debilitating them so thoroughly that they can no longer participate in battle, or rendering them temporarily disabled so they can be captured or overrun. Notably, most chemical weapons do not have a substantial impact on warfighting equipment or properly sealed supplies, meaning that if an enemy force is annihilated or forced to retreat due to chemical weapons, the deploying party can often capture their vehicles, ammunition, and sealed supplies intact.

The properties of specific chemical agents confer additional tactical benefits. Persistent agents — those that linger in the air for hours, days, or even weeks — are particularly effective for area denial, making a patch of land utterly impossible to occupy. They can clear trenches of enemy soldiers, prevent adversary forces from maneuvering through specific zones, or keep enemy forces pinned down in sealed shelters where they may eventually exhaust their supplies. Some persistent agents can even be adapted into thickened, sticky substances that can be launched across or caked over high-value targets, making decontamination and recapture extremely difficult.

Non-persistent agents, which lose their effectiveness much more quickly — sometimes after just a few seconds — offer a different set of advantages. Their rapid dissipation can enable swift advances by the deploying force, clearing one line of enemy trenches at a time and allowing troops to move in and capture those positions once the gas clouds fade. Non-persistent chemical weapons also carry an additional benefit for those willing to use them covertly: they are harder to track and confirm. While some may degrade into chemical compounds identifiable as tracers — evidence that something occurred in an area where their use has been alleged — other poison gases simply disappear without a trace.

Protection and the Asymmetry of Preparedness

Against a weapon so devastating, the ability of both the deploying force and the opposing force to protect their troops from chemical effects is of paramount importance. If one side of a battle is equipped with gas masks, gloves, sealed clothing, and other protective equipment, while the other side has no or limited protections against chemical weapons, then the deployment of chemical agents turns the battle into a foregone conclusion. In areas where enemy troops have been killed, badly wounded, put to sleep, or otherwise incapacitated, a small group of properly equipped soldiers can clear large areas at little risk to their own lives, potentially capturing or even killing the living victims they find.

As a result, militaries often go to great lengths to ensure their troops have protective equipment against chemical weapons if there is any fear that such weapons might be deployed — even if they themselves have brought no chemical weapons to the fight. In the event that troops or civilians are caught in a chemical attack without proper protective equipment, they are fortunate if they have enough time to wet a rag and place it over their nose and mouth to minimize effects on their respiratory system. Their skin and eyes will likely suffer the consequences of toxin exposure before they can protect themselves.

The psychological dimension of chemical weapons cannot be overstated. It is not unheard of for ruling regimes or terrorist organizations to deploy chemical weapons against civilians, exploiting not only their destructive effects on the human body but also the profound and well-documented psychological terror they inflict on a population that knows it might come under chemical attack.

Ancient Origins: Chemical Warfare Before the Modern Era

The history of chemical weapons stretches far further back than many might expect. The Athenian military used plant-derived toxins to taint water flowing through a city they were besieging, while Peloponnesian forces employed sulfur fumes nearly five hundred years before the start of the Common Era. References to rudimentary chemical warfare appear in the Iliad and the Odyssey, in Sun Tzu’s Art of War, in the recollections of ancient Greek and Macedonian historians, and in multiple epics from ancient India. Archaeological evidence has directly supported the use of sulfur dioxide gases against ancient Roman forces in the third century CE.

It was during the 1800s, as humanity’s understanding of toxic chemicals improved dramatically with the onset of the Industrial Age, that various nations began to seriously consider the use of chemical weapons. European powers deployed them against their colonial holdings abroad, including a particularly grim 1845 incident in which French troops in Algeria gassed over a thousand members of a Berber tribe after forcing them into a cave. Chemical weapons were suggested for use numerous times during the American Civil War, although those suggestions were rarely, if ever, realized.

By the waning years of the 19th century, the global community had passed international laws prohibiting the use of shells filled with asphyxiating gases. Notably, America cast the sole vote against the prohibition, claiming it would limit their country’s ‘inventiveness.‘

World War I: The Conflict Synonymous with Chemical Warfare

The period in history most synonymous with chemical warfare is the First World War. The early uses of modern chemical weapons during the Great War are documented extensively, including the very first instance of lethal use on April 22, 1915. On that day, while defending positions north of the Belgian town of Ypres, two colonial French divisions came under attack from poison gas released from cylinders that German specialists had embedded in the ground.

A staggering 167 tons of chlorine gas were released into the air in a grey-green cloud that sent defenders running for their lives. No gas masks were available on the battlefield — the technology had not yet been made operational. Troops caught in the chlorine died agonizing deaths.

The gas attack did not lead to a major break in French lines, largely because German troops were themselves unwilling to advance headlong into a cloud of deadly chlorine.

Later that year, German troops deployed chlorine gas against Russian defenders of Osowiec Fortress, leading to a legendary counter-charge by dying Russian troops in the midst of their agony — an event known as the Attack of the Dead Men. In what was perhaps the most deadly chemical attack in history at the time, Germany killed over a thousand Russians and caused eight thousand more casualties during an attack on the River Rawka outside Warsaw.

The Arms Race of Gas and Masks

The years of the Great War were not only a testbed for humanity’s first modern chemical weapons — they were a period of intense and deadly serious innovation on both sides, encompassing the development of more advanced gases and countermeasures to defend against them.

Troops on both sides quickly learned critical survival basics. Those who ran were more likely to die, both because heavy breathing introduced more gas into their lungs and because movement worsened whatever damage had already been inflicted. Soldiers learned to seek higher ground within a gas cloud, as those closer to the floor experienced higher concentrations. They discovered that a damp cloth over the mouth and nose could make chlorine gas exposure more survivable, and they came to understand that hunkering down and enduring an attack was often preferable to attempting to flee.

Early respirators began appearing along the front lines, and troops improvised their own halfway-decent solutions. Back on the home front, initiatives proved remarkably effective as wives, mothers, sisters, and the elderly worked to create masks to protect their fighting family members. The British public produced a million masks in a single day, though the instructions — published by the Daily Mail — led to masks that proved ineffective or even dangerous to their users.

As the war continued, the Allied Powers developed and deployed their own gas warfare capabilities, while both sides built and distributed more and better masks. Chlorine, limited in efficacy, was rapidly replaced by colorless phosgene. By the war’s end, phosgene would prove responsible for four out of five deaths from chemical weapons, with approximately 36,500 tons manufactured overall.

Far more famous, however, was mustard gas — a thick liquid mist, not actually a gaseous substance — that Germany was the first to deploy. The horrific effects of mustard gas poisoning caused word of its use to spread rapidly across the world until it became synonymous with poison gas warfare during the conflict. Stories of mustard gas victims reached the home front in every participating nation, sowing deep shock and horror as families confronted the reality that their loved ones might return unrecognizable, if they returned at all.

Over the course of the war, Germany and Britain deployed chemical weapons at high rates on the battlefield, while Imperial Russia and the United States each manufactured large amounts of gas that was never used. Chemical weapons were responsible for an estimated 1.3 million casualties by the war’s end.

The Interwar Period and the Geneva Protocol

In the interwar years, chemical weapons saw continued use across the world in the hands of various colonial powers, in newly Soviet Russia, in Morocco, in Libya, and elsewhere. International horror and condemnation surrounding these weapons led to a global effort to ban their use under the Geneva Protocol, signed in 1925.

The Geneva Protocol banned the use of both chemical and biological weapons and demanded the destruction and disposal of certain chemical warfare agents. However, it did not prevent nations from producing new chemical weapons or creating new stockpiles. Enforcement was sorely lacking. It was, frankly, a weak attempt by the international community, even if it may have been the best that could be mustered at the time.

The Protocol was not enough to stop any nation from amassing tremendous quantities of chemical weapons in the following decades, especially mustard gas. By the start of World War II, the Americans had over 87,000 tons, the Soviets over 77,000 tons, the British nearly 41,000 tons, and the Germans nearly 30,000 tons.

World War II: Restraint on the Battlefield, Horror in the Camps

Partly owing to the worldwide horror and shame surrounding chemical weapons use during the Great War, and partly owing to the personal experiences of one German dictator who had himself been gassed during World War I, one of the very few bright spots about the Second World War is that chemical weapons were broadly not used by any side on the battlefield.

There were isolated incidents. Japan deployed mustard gas and a compound called Lewisite in relatively limited quantities in China. Germany dropped mustard gas bombs on Poland in the first days of its invasion, in an act Germany later claimed was a mistake.

The United States shipped chemical weapons to various theaters, including to the city of Bari, Italy, where a German airstrike caused a US cargo ship to spill large amounts of mustard gas — an incident that contributed to the deaths of over a thousand civilians and over a thousand military members and merchant Marines. Italy used chemical weapons more liberally in Ethiopia. Both Britain and the US at least contemplated their use: Britain as a response to a potential Nazi ground invasion, and the US to pave the way for Allied operations on the Japanese Home Islands.

America was ultimately spared from making that decision by virtue of its use of a different weapon of mass destruction — the atomic bomb.

Across the entire war, the US, Germany, the Soviets, Japan, and the British all had chemical weapons mass-produced and ready to deploy. Yet they remained largely unused on the battlefield — about the only thing in World War II that could be described as a dodged bullet. The restraint on all sides was motivated by the fear that each side’s enemies would retaliate with their own chemical weapons, in a pre-Cold War demonstration of the real deterrent value of mutually assured destruction.

The Holocaust: History’s Deadliest Use of Chemical Weapons

To say that chemical weapons were never deployed at scale during World War II would be a lie. The most accurate statement is that they were never deployed at scale on the battlefield. The critical caveat is the Holocaust, where carbon monoxide, cyanide-based Zyklon-B gas, and other poison gases were used to exterminate millions of victims of the Nazi regime.

From Jews to the disabled, from Europe’s homosexual community to its Romani population and beyond, deadly gases were the Nazis’ preferred mechanism of extermination at their many death camps and concentration camps. Some three million people are believed to have been killed by poison gases during this period — well over double the death toll from chemical weapons use across all of World War I, and still the deadliest use of chemical weapons in history. The Holocaust stands as the most horrific chapter in the story of chemical warfare, a grim reminder that the greatest danger posed by these weapons has not always come on the battlefield, but in the systematic machinery of state-sponsored genocide.

Post-World War II: Chemical Weapons in the Cold War Era and Beyond

Unfortunately, while the dual wake-up calls of the Great War and the Holocaust were enough to build a global consensus against chemical weapons, they were not enough to prevent their use entirely. The decades following World War II saw chemical agents deployed in conflicts across the globe, often by state actors willing to flout international norms when it suited their strategic interests.

In 1963, Egypt used chemical weapons at moderate scale against hostile tribesmen in the nation of Yemen, with an estimated 1,500 Yemenis killed via chemical means over the course of that conflict. The United States has been accused of chemical weapons use relating to chemical defoliants, particularly Agent Orange, during the Vietnam War, although the classification of Agent Orange as a chemical weapon remains a messy issue of semantics.

Iraq made liberal use of chemical weapons against Iran during the 1980s, with an estimated 100,000 Iranian casualties including some 20,000 deaths via chemical warfare over the course of the Iran-Iraq War. Iraq’s preferred chemical weapons were nerve agents, which proved to be highly deadly. The same Iraqi regime under Saddam Hussein killed between three and five thousand Kurdish civilians and Peshmerga militants in 1988 — an atrocity that went down in history as the Halabja Massacre, the largest single-instance chemical weapons attack against a civilian population ever recorded.

Chemical weapons also found their way into the hands of non-state actors. In Japan, the cult Aum Shinrikyo carried out a 1995 attack using sarin gas that left thirteen people dead and nearly six thousand at least somewhat affected. Aum Shinrikyo had pulled off a prior chemical attack in 1994, also using sarin, that killed eight and wounded over five hundred. These incidents demonstrated that the threat of chemical warfare was no longer confined to state militaries — terrorist organizations and extremist groups could acquire and deploy these weapons as well.

The Chemical Weapons Convention: A Stronger Framework

In the modern era, chemical weapons prohibitions remain in place from the Geneva Protocol, but the primary anti-chemical-weapon treaty governing the world is the CWC — the Chemical Weapons Convention. Signed in 1993 and entered into force in 1997, the CWC represents a far more sweeping set of prohibitions than the Geneva Protocol ever was. It prohibits not just the use of chemical weapons, but any large-scale development, production, stockpiling, and transfer of these agents.

While there are some exceptions for substances that have a dual use for medical or industrial functions, the vast majority of the world’s most harmful known chemical weapons are covered under the Convention. Signatory nations are expected to destroy all the chemical weapons they possessed at the time of signing and to swear off production of chemical weapons after that time. The Convention comes with enforcement mechanisms and verification measures, and as of early 2021, over 98% of the world’s known chemical weapons stockpiles have been destroyed under the auspices of the CWC. That includes 100% of the declared stockpiles of the United States, Russia, India, Iraq, Libya, and South Korea.

Today, just three nations are not signatories to the CWC: South Sudan, Egypt, and North Korea. Israel has signed the agreement but has not ratified it. While the CWC represents a monumental achievement in arms control, the distinction between the destruction of all chemical weapons stockpiles on Earth and all declared chemical weapons stockpiles on Earth is a critical one.

It is impossible to know with certainty what may exist in the deep recesses of a powerful nation’s defense apparatus, or whether nations like America, Russia, China, India, or the powerful countries of Europe might keep hidden chemical weapons reserves. In each of those nations, there are both a wealth of mass-produced industrial substances and a wealth of less-lethal chemical law enforcement tools — like tear gas — that could theoretically be repurposed for battlefield use if their owner nations ever saw fit to do so.

Syria: Chemical Warfare in the 21st Century

The twenty-first century has provided a small but devastating handful of cases where chemical weapons use remains very much a reality. Perhaps the most prominent modern example is Syria, where before its recent ouster, the regime of Bashar al-Assad leveraged chemical weapons on several occasions during the country’s long and brutal civil war.

In 2013, in the countryside district of Ghouta, the Syrian regime launched a rocket attack that deployed sarin gas in a large-scale chemical assault, killing anywhere from 280 to over 1,700 people depending on which estimate is taken seriously. Sarin attacks and other chemical weapons attacks had rained down across Syria several times before that incident during the Syrian Civil War, but the Ghouta attack marked the most deadly use of chemical weapons since the Iran-Iraq War.

Over the course of the Syrian Civil War, many dozens of chemical attacks by the Syrian regime were reported internationally, including numerous mass-casualty events. Some of the particularly notorious incidents include a 2017 attack in Idlib province that likely killed a hundred or more members of the Hay’at Tahrir al-Sham rebel group, and an attack in the city of Douma that caused between 40 and 50 deaths. Chlorine gas was the Syrian regime’s primary method of destruction, though sarin and mustard gas were used from time to time.

After the Assad regime fell in late 2024, Israel carried out a bombing campaign to destroy a range of potentially dangerous sites, some of which are thought to have been the location of Assad’s continued chemical weapons development program. Also in Syria and Iraq, the Islamic State of Iraq and Syria (ISIS) is believed to have engaged in several dozen chemical attacks, albeit none on a particularly large single-instance scale. The Syrian theater demonstrated with grim clarity that international prohibitions, no matter how comprehensive, are only as strong as the willingness and ability of the global community to enforce them.

Russia: Battlefield Chemicals and Assassination by Nerve Agent

The other modern nation most frequently accused of chemical weapons use is Russia. During its ongoing invasion of Ukraine, Ukrainian authorities insist that Russian chemical attacks have put at least two thousand Ukrainians in the hospital and killed three. In Russia’s case, the nation is not accused of deploying mustard gas, chlorine, or anything of that kind.

Instead, it stands accused of using less-lethal tear gas and similar substances to force Ukrainians out of their trenches and into the path of Russian artillery. Although these particular gases are not typically fatal, they are still classified as chemical weapons by the CWC, and their use has drawn increasing condemnation from around the world as of early 2025.

Beyond the battlefield, Russia has also used chemical agents — particularly its Novichok nerve agents — in multiple assassination attempts. Among the most high-profile cases are the 2018 poisoning of double agent Sergei Skripal in the United Kingdom and the 2020 poisoning of prominent Russian opposition leader Alexei Navalny. Russia claims that Novichok agents are the deadliest nerve agents ever made. These incidents demonstrated that chemical weapons are not only tools of warfare but instruments of state-sponsored assassination, capable of generating international crises and endangering bystanders far from any conflict zone.

On the subject of assassination by chemical agent, North Korea has also used a nerve agent — VX — to assassinate Kim Jong-un’s half-brother, Kim Jong-nam, in an airport in Malaysia in 2017. The brazen nature of the attack, carried out in a crowded public space, underscored the terrifying versatility of chemical weapons and the willingness of certain regimes to deploy them in the most provocative of settings.

The Future of Chemical Warfare: Nearly a Thing of the Past, But Not Yet

In a world where tensions seem to be ratcheting upward each and every day across a wide range of hot zones and conflicts, it should come as some considerable comfort that chemical weapons are used less and less frequently, by a constantly shrinking number of bad actors. The Chemical Weapons Convention has achieved remarkable success in destroying declared stockpiles, and the global stigma against chemical weapons use remains powerful.

But between the small handful of suspected ongoing chemical weapons programs around the world, the potentially larger stockpiles of nations with the diplomatic clout, size, and resources to keep their chemical weapons hidden, and the potential for terror organizations and even lone actors to manufacture these substances, it is far too early to claim that the world has ended its flirtation with chemical weapons. If past action indicates future behavior, then it is entirely likely that someone, somewhere, will make new use of chemical weapons before this decade is out — and perhaps someone after that, and someone after that.

Chemical warfare is nearly a thing of the past, but we are not there yet. The arc of history bends toward prohibition and disarmament, but it does so unevenly, interrupted by the ambitions of dictators, the desperation of terrorist organizations, and the cold calculations of states willing to exploit the cruelest weapons ever devised. The hope — fragile but persistent — is that the international community’s resolve will continue to strengthen, that enforcement mechanisms will grow sharper, and that the day will eventually come when chemical weapons truly belong to history. Hopefully, we will get there soon.

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Frequently Asked Questions

What legally defines a chemical weapon?

A chemical weapon is any toxic chemical capable of causing death, injury, incapacitation, or sensory irritation when delivered into battle or deployed in a conflict. Under international law, a chemical weapon does not need to be lethal to qualify — agents designed to blind, scald, overwhelm with coughing, or render unconscious all fall under the same classification. Context also matters: tear gas is not classified as a chemical weapon when used for domestic law enforcement, but becomes one when deployed in a military conflict.

What are the four main categories of chemical weapons?

The four categories are blood agents (cyanide- or arsenic-based substances that impede oxygen distribution, causing rapid shutdown), blister agents (such as mustard gas, which cause severe chemical burns, water blisters, lung damage, and blindness), choking agents (such as chlorine gas and phosgene, which flood the lungs with fluid and cause victims to choke to death), and nerve agents (such as sarin, VX, and Novichok, which block brain signals to organs, causing convulsions, loss of bodily functions, and often death, with survivors frequently impaired for life).

Why were chemical weapons not widely used on the battlefield during World War II?

The restraint was motivated by two primary factors: the worldwide horror and shame surrounding chemical weapons use during World War I, and the fear of retaliation. All major powers — the US, Germany, the Soviets, Japan, and Britain — had mass-produced chemical weapons ready to deploy, but each side feared that using them would provoke devastating chemical retaliation from their enemies. This dynamic served as a pre-Cold War demonstration of the deterrent value of mutually assured destruction.

How does the Holocaust relate to the history of chemical warfare?

While chemical weapons were largely not used on World War II battlefields, the Holocaust represents history’s deadliest deployment of chemical agents. The Nazi regime used carbon monoxide, cyanide-based Zyklon-B gas, and other poison gases to exterminate approximately three million people — including Jews, disabled individuals, homosexuals, Romani people, and others — in death camps and concentration camps. This death toll is well over double the 1.3 million casualties from chemical weapons use across all of World War I.

What is the Chemical Weapons Convention and how effective has it been?

The CWC, signed in 1993 and entered into force in 1997, prohibits the use, large-scale development, production, stockpiling, and transfer of chemical weapons. Signatory nations must destroy existing stockpiles and cease production, and the treaty includes enforcement mechanisms and verification measures. As of early 2021, over 98 percent of the world’s known chemical weapons stockpiles have been destroyed under the CWC, including 100 percent of declared stockpiles from the US, Russia, India, Iraq, Libya, and South Korea. However, the critical distinction between declared and all stockpiles means that hidden reserves in powerful nations cannot be ruled out.

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