Marking 90 years since Fritz Haber's death, the scientist who helped prevent world hunger with a method for producing synthetic fertilizers but also spearheaded chemical warfare for Germany in World War I.
Few figures embody the clash between groundbreaking innovation and moral controversy as starkly as German scientist Fritz Haber. His discovery enabled the large-scale production of synthetic fertilizers, feeding billions and preventing global famine. Yet, during World War I, he played a key role in developing chemical weapons, which led to the agonizing deaths of tens of thousands—all in the name of German nationalism. The same Germany that once embraced him would later reject him, even turning his own invention against his people.
The Migrating Jew
Fritz Haber was born on December 9, 1868, into an upper-class Jewish family in Breslau—then part of Prussia, now Wrocław, Poland. His father, Siegfried, was a successful businessman who owned a local chemical plant producing paint and medicine. His mother, Paula, died three weeks after his birth due to complications from childbirth. Raised by relatives until his father remarried when he was six, Haber developed over the years a good relationship with his stepmother and half-sisters.
After finishing high school, his father hoped he would join the family business, but Haber instead pursued a passion for chemistry. He studied at the University of Berlin, earning a PhD in organic chemistry for his research on fragrance and flavor compounds. During his studies, he served a year in the artillery corps as part of his military enlistment.
Upon completing his doctorate, Haber returned to Breslau to work at his father’s chemical plant, but their working relationship quickly soured. Spending much of his time training at other chemical plants and at the Zurich Technological Institute, it soon became clear that they could not work together. Haber left the family business and became a junior professor at the University of Jena.
During this period, Haber converted to Lutheran Christianity. Though raised in a home that observed some Jewish traditions, he saw himself as more German than Jewish. He believed conversion would improve his academic prospects, a decision that, if not advantageous, at least did not hinder his career. In 1894, after two years at Jena, he joined Karlsruhe University as a researcher and lecturer. There, he studied carbon combustion processes and gradually shifted his focus to physical chemistry, particularly electrochemistry—the intersection of electrical and chemical processes.
At Karlsruhe, Haber conducted research across multiple fields, contributing to advances in fabric printing and glass electrode technology. He also published three books on electrochemistry. However, his most significant work, which brought him widespread recognition, was his research on atmospheric nitrogen fixation for ammonia production.
Producing Bread From Thin Air
Nitrogen is the most abundant element in the atmosphere, making up about 80% of the air we breathe. It is essential to life, forming key components of proteins, fertilizers, and explosives. However, atmospheric nitrogen (N₂) is not available to humans, animals, and plants. Only certain soil and ocean microorganisms are able to break its strong molecular bond, converting it into compounds with hydrogen or oxygen. These compounds are then absorbed by plants and algae, entering the food chain and sustaining life.
After presenting it to the chemical giant BASF, company scientists and engineers refined the method by replacing costly catalysts with iron-based compounds. By 1913, BASF had begun large-scale ammonia production, securing Germany’s fertilizer supply. Using a process developed earlier by German scientist Wilhelm Ostwald, German industry could then convert ammonia into nitrates— compounds based on nitrogen and oxygen which constitute key ingredients for fertilizers and, such as potassium nitrate (KNO₃) and sodium nitrate (NaNO₃), and are also vital for the explosives industry.
Haber’s breakthrough freed Germany from its dependence on imported nitrogen, helping it sustain agriculture and warfare throughout World War I . However, by the time war broke out, Haber had already shifted his focus to an entirely different endeavor.
Ammonia and its importance – a FuseSchool video on ammonia production.
The Chemical War
By 1911, after 17 years in Karlsruhe, Fritz Haber had gained international recognition and was invited to head the Institute for Physical Chemistry and Electrochemistry in Berlin. A short time after the outbreak of World War I in 1914, as Germany faced accusations of war crimes against Belgium, Haber joined 92 other scientists and intellectuals in signing a manifesto, known as the Manifesto of the Ninety-Three, which expressed unconditional support for Germany's actions. Several prominent German scientists, including Albert Einstein and David Hilbert, refused to sign.
But for Haber, patriotism went beyond petitions. At 46, he volunteered for military service, was promoted to the rank of captain, and was appointed as head of the Chemistry Section in the Ministry of War. Despite Germany’s prior commitment to the 1907 Hague Convention banning chemical weapons, Haber led the development of chlorine gas, assembling a team of chemists and physicists to refine its production, test its effectiveness, and devise methods for its storage and battlefield deployment.
In war time a scientist belongs to his country. Haber (second from the left) instructing field officers on the use of gas shells | Image: Science Photo Library
Scientists around the world harshly criticized Haber for the inhumane use of poison gas, but he remained steadfast in his beliefs, stating “during peacetime a scientist belongs to the world, but during wartime he belongs to his country,” His loyalty to Germany came at a heavy personal cost: following the successful deployment of chemical weapons during the Second Battle of Ypres, which earned him widespread acclaim, his wife, Clara, took her own life using his service pistol. She died in the arms of their 13-year-old son, Hermann, who had heard the gunshot.
Clara Haber (née Immerwahr), also a converted Jew, held a doctorate in chemistry and was a feminist and pacifist. While her husband's actions may not have been the sole reason for her suicide—their marriage was likely troubled—there is no doubt that she struggled to come to terms with them. Haber, on the other hand, did not pause even after this personal tragedy—he did not even remain in Berlin for her funeral, as he hurried east to oversee the use of chemical weapons on the Russian front.
The Prosecuted Patriot
In 1918, the Nobel Committee decided to award Fritz Haber the Nobel Prize in Chemistry, for his development of a process for ammonia production. The decision was met with strong criticism, due to his wartime actions, with British and French scientists even calling for his prosecution for war crimes. Nevertheless, despite the controversy, Haber accepted the prize, which was officially awarded the following year, in 1919.
After the war, Haber returned to his position in Berlin, where he continued working on the development of chemical weapons. Among other projects, he assisted Russia and Spain in developing chemical warfare agents. He also redirected his laboratory’s efforts toward pesticide development, one of which was Zyklon—a cyanide-based gas used to exterminate pests in enclosed spaces, such as food storage facilities and grain silos.
Despite his esteemed status as a scientist and his recognition as a Nobel laureate, Haber struggled to find his place in the scientific community after the war. As a devoted German nationalist, he was deeply disheartened by his country’s defeat, while also grappling with guilt over the widespread use of his chemical weapons—one of the factors that led to the heavy reparations Germany was forced to pay to the victors, contributing to the economic crisis that burdened the country throughout the 1920s. In an effort to generate revenue for Germany, he spent several years researching methods to extract gold from seawater. Ultimately, the project proved financially unviable, and Haber abandoned it.
As the Nazi Party rose to power in Germany, its members criticized the government for employing Jewish scientists, including Haber. His conversion to Christianity and unwavering service to Germany meant nothing to the regime. To them, he was simply “Jewish Haber.” By 1933, he realized he had no future in his homeland and fled with his son to Britain, taking along his second wife, Charlotte, though they were already divorced, and their two daughters.
For several months, Haber wandered through Europe, spending time in Switzerland, France, Spain, and Britain, but he was unable to secure an academic position. Struggling with depression and deteriorating health, he eventually accepted an offer from his longtime friend Chaim Weizmann to head the Sieff Institute, a research center established in Rehovot (which would later become the Weizmann Institute of Science). With no other options, Haber agreed and set out for Palestine. However, he never reached his destination—on January 29, 1934, while staying at a hotel in Basel, Switzerland, he suffered a fatal heart attack, just weeks after his 65th birthday. He was buried in Basel, and at his request, Clara’s remains were later transferred to be laid beside him. Before his death he reportedly repented and expressed regret for his role in the development of chemical weapons.
A stark contrast in attitudes toward Judaism and German nationalism. Haber (left) with Albert Einstein | Source: Science Photo Library
The Death After Death
Haber’s misfortune did not stop at his death. His son Hermann, ended his own life in 1946, a short time following the death of his wife. Three years later Hermann’s daughter, Claire, also committed suicide. She was named after her grandmother and was a chemist like her grandfather. His two children from his second marriage did live a long life.
Family life: Haber (right, in military uniform) with his son Hermann on his wedding day to Charlotte. Left: Clara Haber | Photos: Max Planck Archive, Wikipedia, public domain
Haber’s professional past continued to haunt him even after his death. When the Nazis devised the “Final Solution” to exterminate the Jewish people, someone in the room recalled the Zyklon gas that had been developed in Haber’s laboratory. The original formulation contained hydrogen cyanide along with an added irritant to alert against possible exposure. The Nazis ordered a modified version of the gas without the irritant, packaged in a porous material for rapid release. This variant, later known as Zyklon B, was used to murder over a million Jews in Nazi death camps. Thus, the gas developed under Haber’s direction was ultimately used by the very people he had sought to belong to, in order to destroy a significant portion of the people he had sought to distance himself from.
Over the years, some chose to focus on the positive aspects of Haber’s work and his immense contributions to chemistry. The institute he once led in Berlin is known today as the Fritz Haber Institute, and as part of the scientific collaboration between Israel and Germany, the Fritz Haber Center for Molecular Dynamics was established with support from the Max Planck Society’s Minerva foundation.
“Haber's life was the tragedy of the German Jew – the tragedy of unrequited love,” Albert Einstein once said about the man who had, for a time, been his closest friend. Fritz Haber’s story illustrates how difficult it can be to separate good from evil, even when they coexist in the same person. The brilliant chemist to whom the world owes an abundant food supply was also an ardent nationalist whose actions caused the deaths of thousands—and who did not even spare his own family when national glory was at stake. Haber serves as a sobering reminder that even the most brilliant minds are, ultimately, only human—and not always in the best way.