Distillations magazine

Unexpected Stories from Science’s Past
May 12, 2015 People & Politics

A Brief History of Chemical War

For more than 2,000 years human ingenuity has turned natural and synthetic poisons into weapons of war.


Know Your World War I Chemical Weapons

Three substances were responsible for most chemical-weapons injuries and deaths during World War I: chlorine, phosgene, and mustard gas.

Chlorine gas, used on the infamous day of April 22, 1915, produces a greenish-yellow cloud that smells of bleach and immediately irritates the eyes, nose, lungs, and throat of those exposed to it. At high enough doses it kills by asphyxiation.

Phosgene, which smells like moldy hay, is also an irritant but six times more deadly than chlorine gas. Phosgene is also a much stealthier weapon: it’s colorless, and soldiers did not at first know they had received a fatal dose. After a day or two, victims’ lungs would fill with fluid, and they would slowly suffocate in an agonizing death. Although the Germans were the first to use phosgene on the battlefield, it became the primary chemical weapon of the Allies. Phosgene was responsible for 85% of chemical-weapons fatalities during World War I.

Mustard gas, a potent blistering agent, was dubbed King of the Battle Gases. Like phosgene, its effects are not immediate. It has a potent smell; some say it reeks of garlic, gasoline, rubber, or dead horses. Hours after exposure a victim’s eyes become bloodshot, begin to water, and become increasingly painful, with some victims suffering temporary blindness. Worse, skin begins to blister, particularly in moist areas, such as the armpits and genitals. As the blisters pop, they often become infected. Mustard gas could also contaminate land where it had been deployed. Exposure sensitized victims; further exposure even at lower doses produced symptoms. Mustard gas caused the highest number of casualties from chemical weapons—upward of 120,000 by some estimates—but it caused few direct deaths because the open air of the battlefield kept concentrations below the lethal threshold.


Since the dawn of warfare people have sought new ways to kill one another. Here are some notable moments in chemical warfare through the ages.

600 BCE

The Athenian military taints the water supply of the besieged city of Kirrha with poisonous hellebore plants.

479 BCE

Peloponnesian forces use sulfur fumes against the town of Plataea.


France and Germany sign the Strasbourg Agreement, the first international agreement to ban chemical weapons, in this case outlawing the use of poisoned bullets.


During the French conquest of Algeria, French troops force more than 1,000 members of a Berber tribe into a cave and then use smoke to kill them.


During the American Civil War civilians and soldiers on both sides propose using chemical weapons. Among a multitude of unrealized ideas, New York City schoolteacher John Doughty recommends firing chlorine-gas projectiles at Confederate troops, and Confederate soldier Isham Walker suggests dropping canisters of poison gas from balloons.


A series of international treaties signed by most Western nations bans the use of poison and poisonous weapons in war.


During the first month of World War I the French deploy tear-gas grenades, first developed in 1912 for police use.

German forces fire 3,000 shells containing dianisidine chlorosulfate, a lung irritant, at the British army at Neuve-Chapelle. The British are unaware that they had been subjected to a chemical attack because the chemical is incinerated by the explosive charge.


The Germans fire 18,000 shells filled with the irritant xylyl bromide at Russian troops at Bolinow. The Russians are unharmed because the extreme cold keeps the liquid from vaporizing.

April 22
The German military launches the first large-scale use of chemical weapons in war at Ypres, Belgium. Nearly 170 metric tons of chlorine gas in 5,730 cylinders are buried along a four-mile stretch of the front. In the end more than 1,100 people are killed by the attack and 7,000 are injured.

September 25
The British military uses chemical weapons for the first time against the Germans at the Battle of Loos. They release chlorine gas from cylinders.

December 19
Six days before Christmas, Germans first use phosgene on Allied troops. More than 1,000 British soldiers are injured and 120 die.


July 12
Mustard gas is used for the first time by German forces; it causes more than 2,100 casualties. During the first three weeks of mustard-gas use, Allied casualties equal the previous year’s chemical-weapons casualties.


U.S. research on mustard gas moves from a lab at American University in Maryland to a site called Edgewood Arsenal run by the newly created Chemical Warfare Service. Soon 10% of American artillery shells contain chemical weapons.

The Allies begin using mustard gas against German troops.

October 13–14
A young Adolf Hitler, an enlisted messenger in the trenches at Werwick near Ypres, is temporarily blinded during a gas attack. Hitler is evacuated to a military hospital in eastern Germany and spends the rest of the war recuperating.

November 11
World War I ends with 1.3 million casualties caused by chemical weapons, including 90,000 to 100,000 fatalities, primarily from phosgene.


The Geneva Protocol is adopted by the League of Nations. The treaty bans the use of chemical and biological agents in war but does not prohibit the development, production, or stockpiling of such weapons. Many countries sign the treaty with reservations permitting them to respond in kind if attacked with chemical weapons.


Benito Mussolini drops mustard-gas bombs in Ethiopia to destroy Emperor Haile Selassie’s army. Despite Italy being a signatory of the Geneva Protocol, the League of Nations does not stop its use of chemical weapons.


German chemist Gerhard Schrader completes the synthesis and purification of tabun, a potent nerve poison. His intention is to build a pesticide, not a chemical weapon. The chemical he creates is so potent that army researchers call it taboo, or Tabu in German, from which it takes its name.


During World War II poison gases are used in Nazi concentration camps to kill civilians and by the Japanese army in Asia. Nerve agents are stockpiled by the Nazis, but chemical weapons are not used on European battlefields.


The Nazis force prisoners at the Dyhernfurth concentration camp to produce tabun. Laborers are often denied medical treatment when exposed to lethal doses of the poison.


British serviceman Ronald Maddison dies of sarin poisoning after being purposefully exposed to the toxin at Porton Down military facility.


The United States uses napalm and the herbicide Agent Orange during the Vietnam War, sparking national and international protest.


Egypt uses mustard gas and a nerve agent in Yemen to support a coup d’état against the Yemeni monarchy.


The Biological and Toxin Weapons Convention is completed. Combined with the 1925 Geneva Protocol, the new accord bans the development, production, and possession of biological weapons. The accord has no mechanism to ensure compliance.


During the Iran-Iraq war Iraq uses chemical weapons, including tabun, against Iran and Iraq’s Kurdish minority. United Nations experts confirm Iraq’s use of chemical weapons, but there is little international outcry. Iran initiates its own chemical-weapons program in retaliation.


The Chemical Weapons Convention is signed. Beginning in 1997, the disarmament agreement bans the development, production, stockpiling, and use of chemical weapons.


The Syrian military uses sarin gas against civilians during the Syrian Civil War; hundreds are killed. Bashar al-Assad’s government relinquishes its arsenal of chemical weapons after threats of U.S. air strikes.

Fritz Haber, Life and Death

In the early evening of April 22, 1915, a greenish-yellow fog wafted across the trenches near Ypres, Belgium, terrifying and asphyxiating unprepared French troops. This opening act of chemical warfare had been in planning for months and was carried out by many people: installing the nearly 6,000 gas cylinders alone required scores of German hands.

Yet Fritz Haber—and he alone—is the person we most identify with these weapons, and rightly so. Although many have invented, developed, or deployed chemical weapons throughout history, Haber used his considerable intelligence to militarize chemistry in World War I; in April 1915 at Ypres he witnessed the first fruits of this labor, the first large-scale use of chemical weapons in contemporary warfare. He remained an unfailing ambassador of such weapons, arguing until his death in 1934 that they are a more humane form of weaponry than modern artillery.

After World War I the Allies deemed Haber a war criminal for his work, and he lay low briefly in Switzerland until his name was removed from the wanted list. Haber continued to research and to promote chemical weapons after the war. As Dietrich Stoltzenberg describes in his comprehensive biography of the man, after World War I, Haber helped improve a one-step process for making mustard gas; aided Russia in developing its first chemical-weapons plant by recommending a colleague to Russian emissaries looking for advice; and until 1933 helped the German military in its secret chemical-weapon armament and research program, in direct contravention of the peace treaty signed in 1919.

Yet Haber’s work has also deeply benefited humankind. His discovery of the Haber-Bosch reaction underpins the green revolution: the Nobel Prize–winning strategy for synthesizing ammonia paved the way for inexpensive fertilizers, with enormous benefits to agriculture. He also helped lay the foundations of 20th-century electrochemistry and physical chemistry.

Haber’s Janus-faced scientific achievements were mirrored in his personal relationships. To some he was a great friend. According to one of his closest confidants, the chemist and fellow Nobel laureate Richard Willstätter, Haber was loyal, devoted, and entertaining. “The most beautiful trips were the ones I took with Fritz Haber,” Willstätter wrote in his memoirs. “They were hours of friendship in which I came to know and understand his individuality, his noble mind, goodness of heart, wealth of ideas, and his boundless, extravagant drive.” Haber also maintained strong bonds with Albert Einstein, despite their vast differences in opinion about everything from German politics and national pride to the ethics of chemical weapons. During his travels he wrote Einstein postcards in rhyme—as he did for many of his close friends—that were often humorous, ironic, or both.

Yet Haber’s strong ego led to two failed marriages and rocky familial relationships. Haber’s second marriage, to Charlotte Nathan, ended in divorce; his first, to Clara Immerwahr, ended when she committed suicide. Their son, Hermann, discovered his mother in a pool of her own blood, but Haber left the boy soon after for the eastern front to help deploy the chemical weapons he invented. In such ways Haber often prioritized his intellectual progeny over his biological offspring. It is perhaps no surprise that according to historian Ute Deichmann, years later Hermann and his wife declined an invitation to attend a scientific memorial for Haber. In a letter Hermann’s wife remarked, “One has no right to celebrate a person dead, whom one would not tolerate alive today.”

Haber’s failures as a family man may have stemmed from his own rocky childhood and poor father figure. As Stoltzenberg notes, Haber’s mother died in childbirth, and his father blamed the son for the loss of his new bride. The father-son relationship never recovered. Despite Haber’s propensity for science, his father disapproved of his son’s “chemical games” and wanted him to join the family dye trade business. Haber obeyed, but the two simply could not get along. In the end Haber was freed of his domineering father’s influence and allowed to pursue his dream.

Haber’s life ended cruelly. He deeply identified as a German and used his skills and intelligence to benefit his country in war and in peace. His Nobel Prize gave him fame, and he took pride in his status as a war hero. Yet by the end of his life his country saw him as little more than a dispensable Jew, even though Haber had converted to Christianity as a young man.

In 1933 Hitler ordered Jews removed from positions in the civil service. After trying but failing to help many of his Jewish colleagues, Haber stepped down from his founding position at the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry. He spent the last year of his life wandering around Europe heartbroken—both literally and figuratively. He died in Basel, in 1934, of a heart attack.

Terrible Ingenuity

The German soldier with the worrisome tale was captured by Allied forces in Tunisia on May 11, 1943. He told British interrogators that he was a chemist, far afield from the Berlin lab where he had been working on a new chemical weapon with “astounding properties.” The poison was colorless and nearly odorless, and could asphyxiate its victims in less than 15 minutes—a tale that sounded straight out of a crime novel. But interrogators believed the story and sent a secret 10-page report to British military intelligence, notes Jonathan Tucker in War of Nerves: Chemical Warfare from World War I to al-Qaeda. Yet British intelligence officials doubted the truth of the report and did nothing—a blunder that could have had lethal repercussions for the Allies in World War II.

Not only had the Germans discovered a new family of chemical weapons—nerve agents called tabun, sarin, and soman—that were far more potent than anything the Allies had at their disposal; Hitler had already come close to approving their use on Allied forces after the German army’s defeat in Stalingrad during the winter of 1943. The Nazis also had reconfigured the Dyhernfurth forced-labor camp in present-day Poland to produce thousands of metric tons of tabun.

Although many senior military officers encouraged Hitler to deploy their powerful new chemical weapon, he waffled, likely for two reasons. First, as a victim of gas poisoning during World War I, Hitler recoiled from using chemical poisons on troops—though he had no qualms about deploying poisons on concentration-camp prisoners. Second, German military intelligence was unsure whether the Allies had also discovered nerve agents since some of the foundational research had been done in England. Any Allied retaliation on German civilians could have been catastrophic. President Franklin D. Roosevelt said in June 1943 that “any use of gas by any Axis power will immediately be followed by the fullest possible retaliation upon munitions centers, seaports, and other military installations through the whole extent of the territory of such Axis country.”

Yet the Germans overestimated Allied capabilities: the Allies had no nerve poisons at their disposal. The Germans had only acquired the new family of chemical weapons by serendipity. In 1936 a chemist named Gerhard Schrader first synthesized tabun at the German chemical company IG Farben. He was aiming to create an insecticide that would allow Germany to increase its food production. But after Schrader nearly poisoned himself and his lab mates with mere drops of his newly synthesized insecticide, the company realized that tabun was better suited to military applications and forwarded the discovery to German military researchers. Schrader experienced eye irritation, pupils constricted to pinpoints that dimmed the surrounding world, a runny nose, and shortness of breath. Luckily for him he avoided the next stage of nerve-agent poisoning: intense sweating, stomach cramping, muscle twitching, a loss of consciousness, and asphyxiation.

By 1943 a team of German military scientists developing tabun had also designed another nerve agent called sarin that was six times more potent than tabun. The German Nobel laureate Richard Kuhn was called on to help discern why the new poisons were so deadly. He soon discovered that these nerve agents interfere with a critical enzyme, cholinesterase. In the process Kuhn also discovered a third nerve agent: soman.

As the Nazis scaled up production of tabun at Dyhernfurth, they used 20 of the camp’s prisoners as test subjects in nerve-agent experiments; a quarter of them died in agony. Dyhernfurth prisoners also were forced to travel alongside train shipments of the nerve agents—effectively used as human canaries to detect leaks of the poison gas. At the end of the war, after two-and-a-half years of production, the factory at Dyhernfurth had produced almost 12,000 metric tons of tabun. Some 10,000 tons were loaded into bombs for the Luftwaffe, and another 2,000 tons were encased in artillery shells. Meanwhile, Tucker writes that hundreds of forced laborers working at Dyhernfurth “had died of exhaustion, malnutrition and toxic exposure.”

In February 1945, as the Russians marched toward Berlin, the Nazis quickly abandoned the Dyhernfurth factory. Hundreds of forced laborers were transferred by foot and in open wagons to another concentration camp, Mauthausen. Two-thirds of them died from exposure to freezing temperatures. The Gestapo tracked down the survivors at Mauthausen and killed them to get rid of witnesses.

Desperate to prevent the Red Army from capturing nerve-agent know-how, the Luftwaffe tried and failed to destroy the Dyhernfurth factory from the air. The Soviets discovered the tabun plant and a sarin pilot plant and carried the plant’s machinery back home. British and U.S. military officials panicked when they learned of the existence of these nerve agents and that the Russians had nabbed an entire factory for making tabun. They hunted down German scientists familiar with nerve-agent production and used their know-how to create and stockpile these new weapons. Thus began a chemical arms race that for decades would parallel the nuclear arms race.

The Dark Side of British Chemical-Weapons Research

On May 6, 1953, Ronald Maddison, a 20-year-old British soldier, agreed to participate in a medical experiment at the Porton Down military research facility. The promised compensation was tempting: a three-day pass and 15 shillings, which Maddison wanted to use to buy an engagement ring for his girlfriend. But Porton Down officials did not disclose that they intended to use him as a human guinea pig to study the effects of the deadly nerve agent sarin.

Scientists placed 200 milligrams of pure sarin on a piece of flannel attached to Maddison’s left forearm. Within half an hour Maddison was drenched in sweat and had lost his hearing; he then fell unconscious. At this point scientists injected him with atropine, a treatment for nerve agents, and took him to the hospital; but Maddison soon stopped breathing and was pronounced dead. Officials at the highest levels rushed to cover up the death. According to an inquiry conducted decades later, the home secretary had advised the coroner that an “inquest should be held in-camera [i.e., in private] on grounds of national security. Must not be published.”

Maddison was just one among thousands of people used in chemical-weapons experiments at Porton Down. The facility was established by the British military in September 1915, just months after the surprise poison-gas attack at Ypres. Built on 3,000 acres of countryside about 85 miles southwest of London, Porton Down’s aim was to test and research chemical weapons. Scientists at Porton Down, desperate to catch up with their German counterparts, examined 200 substances during World War I. Many of these experiments relied on living creatures, including dogs, goats, and humans.

By modern standards the tests seem absurdly irresponsible: they often took place outdoors, and given the nature of gases, the toxic chemicals tended to drift out of the facility’s confines and into civilian areas, notes Rob Evans, author of Gassed. Another test required a fleet-footed cross-country runner to stand in a field near an arsenical smoke cloud. His job was to judge the cloud’s potency by sniffing and, when the wind changed direction, to run after the cloud and get in front of it.

Evidence suggests many people were tested without consent or without full awareness of what was involved in the Porton Down trials. Major-General Charles Howard Foulkes, commanding officer at Porton Down, wrote that in the military station’s first six months “the greatest difficulty was experienced in getting sufficient men to carry out the experimental work.” Cooks, orderlies, and clerks were diverted from their usual jobs to participate in the experiments, Evans notes.

By the close of World War I, Britain had studied the effects on humans of 96 compounds. But the end of the war did not end the use of human guinea pigs. Instead their numbers rapidly increased. Through the 1950s more than 18,000 humans—mostly soldiers, often referred to by the sanitized euphemism “observer” in official reports—were exposed to a wide variety of established and prospective chemical weapons as well as psychoactive drugs. The nature and riskiness of the experiments were often withheld from these subjects.

In 1970 Porton Down’s classified records began to reach the light of day. Maddison is the only known death, but many human experimental subjects suffered health problems after exposure, either immediately (for example, by falling into a coma) or years later (subjects had higher rates of cancer). In 2004 the jury of a public inquest into the Maddison case deemed that the young man was “unlawfully killed” at Porton Down. More than half a century after his death Maddison’s family received £100,000 in compensation.

“Maddison’s death was an accident waiting to happen that resulted from an inadequate level of disclosure and an understatement of risks, despite the fact that there was widespread consensus in the United Kingdom that the principles of the Nuremberg Code should govern these types of experiments,” notes Ulf Schmidt, the historical expert appointed to the inquest.

“None of the evidence that I have seen indicates that any of the experimental subjects, including Maddison, was ever informed about the specific objective of the experiments,” Schmidt adds. “And I believe it to be rather unlikely that any man in his right mind would have volunteered for such an experiment.”

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