Forbidden History - The Father of Chemical Warfare: Hero or Monster?

Episode Date: August 4, 2026

In this week's episode of Forbidden History, Dominic Selwood explores the extraordinary life and contested legacy of Fritz Haber, the Nobel Prize-winning chemist whose discoveries transformed both agriculture and warfare, leaving behind one of history's most complex moral debates. Cast List: Eric Meyers: Narrator Dominic Selwood: Author & Historian Learn more about your ad choices. Visit megaphone.fm/adchoices

Welcome to the Forbidden History Podcast. Be sure to catch our Patreon exclusive Inner Circle series, featuring live expert interviews and deep dives into your favorite topics. Thanks for supporting the show. It's April 1915. The First World War has been raging for almost a year, and French troops near the small Belgian town of Ipul peer over the top of their trench to see an enormous greenish cloud spreading over no

man's land, the leaves on the trees wither as it passes. Birds fall from the sky, and then it reaches the men. They fall to the ground convulsing, their skin turning blue as they suffocate. It was the first large-scale chemical attack in history. Figures are difficult, but some say that in less than 10 minutes on a Belgian spring day, a thousand French and Algerian soldiers were dead and a further 4,000 were wounded. This new weapon is chlorine gas, the latest addition to Germany's arsenal. Watching over its first use in war is its inventor, Fritz Haber, and chlorine will be merely the beginning.

What he had begun with chlorine gas, he then evolved also to study it with fosgene and eventually mustard gas. And together these three are the three ghastliest chemical weapons of the First World War. Fritz Haber would become known as the father of chemical warfare, and yet his story is not merely that of an immoral scientist. It's also the story of a man who saved humanity, and today half the world's population owe their lives to him. To take us through the brilliance, the controversy, and the consequences of Haber's life,

His historian and author Dominic Selwood. His ammonia fertiliser process saved lives initially, and his chemical weapons work took lives immediately. Aside from notoriety, Harbour's work also came at a great personal cost. Appraisals of his work come down to patriotic duty and understanding at the time of total war on the one hand and the sheer horror of chemical warfare on the other. You're listening to Forbidden History,

the podcast series that explores the past's darkest corners, sheds light on the lives of intriguing individuals, and uncovers the truth buried deep in history's most controversial legacies. It's just possible that if Fritz-Hawber had been born at any other time or in any other place, no one would have ever heard of him. But his birth comes at a crucial point in history. Fritz Harbour was born on December 9, 1868, in Breslau, which today is in Poland, but then was in the German kingdom of Prussia.

And he grew up, like many of his contemporaries, as a very strong German nationalist. He was fascinated by science, and he was clever. One month after Haber's third birthday, Germany is unified, and Prussia becomes part of the German Empire. Growing up in this new Germany is an exciting time for anyone interested in science, because the country's chemical manufacturing industry is about to boom. Firms like Baer, Agfa, and BASF, to this day still the world's largest chemical company, are pioneering new dyes, new pharmaceuticals, and soon, the chemistry of light itself, giving birth to photography. As a child, Haber experiments with chemistry at home,

and it's no surprise to any of his contemporaries that it is chemistry he chooses to study when he goes to university. He attended leading universities including Heidelberg, where he studied under Bunsen of Bunsen-Berner fame, then Berlin, and he specialized in physical chemistry and industrial chemistry. By the time Haber leaves university, Germany is the world's chemical manufacturing superpower, and there's no shortage of exciting places for a young graduate to work. With these chemical giants, in competition with each other to create the next big thing, each has a huge research and development budget

and industrial laboratories working to turn chemistry into profit. But Haber faces two barriers. His training is in physical chemistry, not the industrial chemistry the big firms demand. And he's Jewish, just as anti-Semitism is beginning to take root in German science and industry. Those two factors send him into an unconventional start to his career as he works to gain the required experience.

At the age of 24, hoping to get on professionally, he converted from Judaism to Protestantism. And he soon got prestigious jobs in Zurich, in Jena and in Karshruhe. By moving between laboratories and trying his hand at industrial work, Haber realizes that factory chemistry isn't for him. He wants to use chemistry to change people's lives. not simply to turn a profit. And it's at Karlsruhe in southwest Germany that he begins tackling the biggest issue humanity is facing. Harper was interested in solving actual problems that were around him. And in the early 1900s, one of those was that Europe was running into

serious difficulties in fertilizing its crops. The vast shipments of bird droppings from South America that they had relied on were drying up, and there was no obvious alternative. Nitrogen is in the air all around us, but not in a form plants can use, and so for thousands of years humanity has turned to some often bizarre sources of plant-friendly nitrogen. The ancient bones of Egyptian slaves, horse skeletons from the Napoleonic wars, the craniums of North American bison, all have been dug up and ground to dust in the world's bone mills to give crops the nutrients they need to grow. But by the early 20th century, natural sources can't keep pace with population growth,

and a lack of fertilizer is threatening to unleash a global famine. In 1904, Haber turns his attention to this precise problem, a way of manufacturing plant-friendly nitrogen artificially. Five years later, he has a breakthrough. So the innovation Harbour is best remembered for is making ammonia in what became known as the Harbour process and this involved combining nitrogen and hydrogen under high pressure and temperature to create ammonia. Harbour manages to break a chemical law that everyone had thought unbreakable, under very high pressure and in the presence of an osmium and uranium catalyst,

the ammonia he creates is a nitrogen-containing compound that plants can use, but while his process is groundbreaking, it can only make minute quantities. To make any kind of difference to the world, Haber would need Germany's chemical industry. The industrialist Karl Bosch became interested in Harbour's work, and together they perfected a process for creating ammonia on an industrial scale. This was and still is known as the Harbour Bosch process,

and they rolled it out from their BASF plant in Ludwigshafen. The expensive catalyst is replaced with one based on cheap iron, and in a factory the size of a small city, the fruits of the most important chemical discovery of the 20th century are produced at scale. Famine is averted, and even more than that, the resulting furtive. fertilizer enables our planet to support more and more people. In 1900, the global population was 1.6 billion people. It is now 8.3 billion, thanks in large part to the Harbor Bosch process, which, quote unquote, made bread out of air.

The process makes Haber internationally famous, and in 1911 he's appointed the founding director of the Kaiser-Vilhelm Institute, with the task of elevating German science and competing with France and Britain. Had Haber stopped at ammonia, history would remember him as a savior, but the age he lives in is about to change. Europe's race for scientific supremacy

is sliding toward war, and Hobber's genius, the same brilliance that feeds millions, is about to be redirected into chemistry that kills on a vast and terrible scale. When World War I broke out, science was immediately mobilised by all countries, and Harbour placed his institute at the service of the state. Like many academics, he was happy to help,

as this war was seen for the first time in history really as a total war, in which every skill and sector of the economy had to be deployed in the war effort. So he allowed his ammonia process to be used for explosives and munitions. which was a vast boost to the German war effort. Haber believes that Germany faces a long war of attrition, but that chemistry can break the stalemate and lead to a rapid German victory. The Kaiser-Vilhelm Institute becomes a military laboratory in all but name.

One area he turns his attention to is the spread of typhus, a disease which is ripping through the ranks of the German army. He develops hydrogen cyanide-based pesticides and fumigation chambers to kill the lice that carry it. However, infamously, he leads Germany's research into chemical weapons. Dismissing tear gas as too weak, he directs research efforts towards chlorine. At the time, chemical warfare was illegal. Others were doing it. The French had been first deploying tear gas leading to an escalation. But there is a big difference between tear gas and chlorine gas.

Technically all of it was against the various conventions, including the Hague conventions, but all sides argued that this was necessity. As a fervent German nationalist, Haber sees chemical weapons as a way of harnessing his scientific skills to serve the fatherland. And as history repeatedly shows, when patriotism combines with the desperation of war, moral boundaries dissolved. Largely under his direction, German chemists developed cylinder-released chlorine gas

to use on the battlefields. At the Second Battle of Epe, which was on April 22nd, 1915, he released approximately 6,000 cylinders of chlorine gas, awakening the world to a brand-new terror. After witnessing that initial use of chlorine gas at Eap, Haber becomes the de facto head of Germany's chemical weapons program and is invited to dine with Kaiser Wilhelm II himself. Haber would later claim that death by gas is no more cruel than death by artillery,

a justification that horrifies many, few more so than his own wife. He had married Clara Immanvar before the war. She was a brilliant chemist, one of the first women in Germany to be awarded a PhD, and the first woman PhD from Breslau University. When he returned home from Iphe after that initial deployment, she challenged him. And despite Fritz's belief that death by gas was no worse than any other form of wartime killing,

his work and her opinions utterly devastated her. She went upstairs, took his service revolver and shot herself. Haber would later claim to be haunted by his wife's ghost, but he has no time to mourn her now. The very next morning, he leaves for the battlefield to oversee a gas attack on the eastern front. Throughout the war, he would go on refining his techniques for deploying the gas more efficiently,

and under his leadership, Germany would develop even more chemical weapons. Chlorine and fosgene gases caused agonizing and permanent respiratory damage. Mustard gas caused blistering and severe eye-eastern. injuries. Many people were killed by these gases, but the real horror lay in the vast numbers who were permanently wounded or crippled from it. There was also a terrifying psychological aspect, with fear of gas and gas attack, a constant presence entrenched life. By the end of World War I,

after all sides had gone resolutely chemical, perhaps 190,000 tonnes, of military gas had been produced, resulting in an estimated 90,000 deaths and 1.3 million casualties. By the end of the First World War, the man who had once been humanity's savior, had become the architect of a form of warfare so terrible even the Nazis would not use it. The Allies brand him a war criminal, and he flees to neutral Switzerland to evade capture. With his reputation in tatters, what happens next is unexpected. The war ended in 1918 and astonishingly in 1919, the Nobel Committee awarded the prize in chemistry for 1918 to Harbour, but for his pre-war ammonia process.

Even at the time, this was immensely controversial, as Harbour was by now widely viewed in very ambivalent ways. Some valued him as a national asset, but most viewed him as an infamous figure for his work with chemical weapons. Large numbers boycotted his Nobel ceremony. In his Nobel Prize speech, Hobber emphasizes that his achievement was not merely in chemistry,

but in pushing past scientific consensus, ignoring those who said that synthesizing ammonia simply couldn't be done. And as he embossized, on his next project, pushing past consensus will be an understatement. The harbour continued after the war to work as a scientist, and he focused on trying to rehabilitate and reintegrate German science into the international scientific community. One thing he worked on was conscious of the crippling reparations imposed by the Treaty of Versailles on Germany. He set about trying to extract gold from seawater to help Germany pay the impossibly

unrealistic fines, but to his immense frustration, failed in this task. With his calculations out by several orders of magnitude, Haber returns to Germany empty-handed. But there he finds his wartime expertise will soon be in demand once more. The end of the war has seen civilians displaced across Eastern Europe, while millions of soldiers are demobilized and heading home. And in crowded refugee camps and barracks like, lice are once again spreading typhus. Germany fears the disease spreading westward, and Haber, as someone who already had expertise in lice eradication, is the ideal candidate for the new post of National Commissioner for

Pest Control. Under his direction, he and his team develop and standardize hydrogen cyanide fumigation as the method to kill lice, and devise sealed chambers where clothing and bedding could be de-Loust with gas. His chambers become national infrastructure, saving thousands of lives. But a new chapter in Germany's history is about to begin, and he will be forced to leave the country of his birth for good. By the 1920s, the trauma of defeat in war, economic collapse, and the rise of racial ideology are combining, and Jews become the convenient scapegoat for everything that has gone wrong for Germany.

Haber, despite his conversion to Christianity, finds himself increasingly isolated, and when the Nazis are voted into power, the isolation of Jews becomes law. The next chapter of Harbour's life starts when the Nazis came to power in 1933. To his intense disappointment, it turned out that his service to the state and his seniority in the scientific community counted for nothing in a nation that had become third. fixated on racial purity. The Nazi's racial laws required the dismissal of non-Aryan staff from research posts, and Harbour had to oversee dismissing Jewish staff. He tried to ignore the orders, delayed and eventually resigned. And despite his deep love for Germany, he left the

country in protest at the racial ideology that was now being embedded in all sectors. With nowhere to go, a scientist at the University of King, in England, offers him a temporary position there. But as the father of chemical warfare, he is scorned by his British colleagues, and he leaves not long after arriving. On route to a new scientific post in Palestine, he dies in Switzerland of heart failure, brought on by stress at the age of 65. And so ended a life of profound contradictions,

of research that saved lives and research that took them. that took them. He would never live to see what happened to the country of his birth under the Nazis. He'd never know that years later, the pesticide he had helped to create would be used under the trade name Zyklon B to murder his half-sister, his brother-in-law, his nephews, and millions of other Jews in gas chambers across Europe. But he'd also never lived to see his Haber-Bosch process become one of the pillars of the modern world. How the the fertilizer it enables would sustain billions of lives around the globe to this day. It's estimated that some 50% of the nitrogen atoms in the average human body, you and me,

today derive from the Harbour Bosch process. What is known as the Harbour Paradox is that his ammonia fertilizer process transformed agriculture globally and save lives initially, and his chemical Weapons' work took lives immediately. Appraisals of his work come down to patriotic duty, and understanding at the time of total war on the one hand, and breaking international rules and the sheer horror of chemical warfare on the other. In the end, Fritz-Hawber leaves us with a legacy that refuses to sit neatly on one side of the moral ledger. His chemistry fed the world and his chemistry scarred it. And perhaps that's the uncomfortable truth

his story forces us to confront. Scientific brilliance can lift humanity or wounded, depending on the moment, the politics, and the choices we make. Haber never lived to see the full reach of his work. Yet the world shaped by his chemistry is still the one we inhabit today. Thanks for exploring the past with us today.

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