The Scientist Who Killed Millions and Saved Billions: Fritz Haber

“During peace time a scientist belongs to the World, but during war time he belongs to his country.” - Fritz Haber

There are very few people in history who can genuinely be credited with helping to keep billions of people alive. There are even fewer who can simultaneously be credited with helping to introduce one of the most terrifying weapons ever used on a battlefield. Fritz Haber managed both. Every time synthetic fertiliser is spread across farmland, the world continues to benefit from chemistry that Haber helped make possible more than a century ago. Yet the same scientist personally supervised the first large-scale lethal chlorine gas attack of the First World War. Depending on which part of his life you examine, Fritz Haber can appear either as one of humanity’s greatest scientific benefactors or one of the men who helped make modern warfare considerably more horrific.

Fritz Haber was born in Breslau, Prussia, now Wrocław in Poland, on 9 December 1868. He came from a Jewish family and his father, Siegfried, was a successful chemical merchant. Haber studied chemistry at several German universities, including Heidelberg and Berlin, before eventually pursuing an academic career. As a young man he converted to Christianity, a decision made during a period when many assimilated German Jews regarded conversion as a way of removing barriers to professional advancement and demonstrating their German identity. Whatever his motivations, Haber considered himself intensely German and would later display a level of patriotism that shaped both the greatest achievement and the darkest chapter of his life.

In 1901 Haber married Clara Immerwahr, herself an accomplished chemist who had become the first woman to earn a doctorate at the University of Breslau. Their marriage was complicated and increasingly unhappy. Clara struggled to maintain a scientific career while also being expected to manage the household and raise their son Hermann, while Fritz’s career accelerated dramatically. In a letter written in 1909 she complained that what Fritz had gained during their marriage, she had lost. The significance of their relationship would become considerably darker during the First World War, but by then Haber had already made the scientific discovery that would ensure his name survived long after both of them were dead.

The problem Haber attempted to solve involved nitrogen. Plants need nitrogen to grow, but although the atmosphere around us is approximately 78 per cent nitrogen, plants cannot simply pull it from the air in the form in which it naturally exists. Farmers therefore depended heavily on naturally occurring nitrogen compounds found in manure, guano and mineral deposits such as Chilean nitrate. As the world’s population increased, scientists worried that agriculture could eventually become incapable of producing enough food. There was an almost unlimited quantity of nitrogen directly above every farmer’s head, but nobody had developed an economical method of turning it into something crops could use.

Haber eventually succeeded by combining nitrogen and hydrogen under extremely high pressure and temperature in the presence of a catalyst, producing ammonia. In 1909 he demonstrated a workable laboratory process, and the German chemical company BASF acquired the technology. Engineer Carl Bosch then faced the enormous challenge of turning Haber's laboratory experiment into an industrial system capable of operating continuously on a massive scale. Bosch succeeded, and by 1913 synthetic ammonia was being produced industrially. The system became known as the Haber-Bosch process and fundamentally changed agriculture because humanity was no longer completely dependent on naturally occurring deposits of fixed nitrogen.

The significance is difficult to exaggerate. Synthetic ammonia could be converted into fertiliser and spread across farmland, dramatically increasing agricultural productivity. Modern food production still depends heavily on the process, and a substantial proportion of the nitrogen contained within human bodies today ultimately came from industrial nitrogen fixation. Haber had effectively discovered a way of making what became known as “bread from air”. It was an extraordinary achievement and would eventually earn him the Nobel Prize. Unfortunately, ammonia had another extremely useful application.

Nitrogen compounds are also required to manufacture explosives. When the First World War began in 1914, Britain’s naval blockade threatened Germany’s access to imported nitrates. Without an alternative supply, Germany would eventually have struggled to manufacture sufficient explosives and ammunition. Haber’s ammonia process provided that alternative. The same chemistry that could place fertiliser onto a farmer’s field could also provide the raw materials needed to manufacture explosives for artillery shells. Haber’s great discovery therefore possessed two completely opposing personalities. One helped grow crops, while the other helped Germany continue fighting a world war.

Haber embraced the German war effort enthusiastically. He placed both himself and his institute at the disposal of the military and became heavily involved in researching chemical weapons. Trench warfare had created a military stalemate across the Western Front, and Haber believed chemistry might provide a method of breaking it. His most infamous proposal involved releasing chlorine gas towards enemy positions. Chlorine attacks the respiratory system and, at sufficiently high concentrations, causes victims to suffocate as the lungs are severely damaged. Haber was not merely a scientist sitting safely in Berlin suggesting experiments for others to perform. He travelled to the front and personally supervised preparations for the attack.

On 22 April 1915, near Ypres in Belgium, German forces opened thousands of cylinders containing chlorine. The wind carried an enormous cloud of poisonous gas towards Allied positions. Soldiers initially had virtually no protection against it and many had no understanding of what was approaching them. Men began coughing, choking and struggling to breathe as the yellow-green cloud moved across the battlefield. The attack opened a large gap in the Allied line and marked the beginning of modern large-scale lethal chemical warfare. What Haber had created in the laboratory had now been demonstrated on human beings.

Haber defended chemical warfare and believed there was no particular moral distinction between killing someone with gas and killing them with artillery or bullets. He also hoped that a sufficiently terrifying new weapon might help end the war more quickly. His attitude was summarised perfectly in the quotation associated with him: during peace a scientist belonged to the world, but during war he belonged to his country. Other nations quickly developed their own chemical weapons, and the supposedly war-ending innovation became another method of killing. Chlorine was followed by even more dangerous substances such as phosgene and mustard gas, and by the end of the First World War chemical weapons had killed tens of thousands and injured more than a million people.

Only days after the attack at Ypres, tragedy struck inside Haber’s own home. On the night of 1 to 2 May 1915, Clara Immerwahr took Haber’s military pistol, went into the garden of their home and shot herself. Their teenage son found her dying. The timing has inevitably produced one of the most famous stories associated with Haber: that Clara, horrified by her husband’s chemical warfare work, killed herself as a protest against what he had done.

The truth is more complicated. Clara’s precise motivation for suicide remains unknown. Later accounts portrayed her as an outspoken pacifist who regarded chemical warfare as a corruption of science, but modern historical research has found that the evidence for this version is much weaker than is often suggested. Her unhappy marriage, depression, loss of her scientific career, personal difficulties and the pressures of the war may all have contributed. Disagreement over Fritz’s military work may also have played a part, but it cannot be established as the sole reason. What is known is that the following evening Haber left for the Eastern Front, having been unable to obtain permission to remain at home.

The war ended in German defeat in 1918, but Haber’s scientific reputation remained enormous. He was awarded the 1918 Nobel Prize in Chemistry for the synthesis of ammonia from its elements. The decision was controversial because the same man being honoured for improving mankind’s ability to produce food had so recently been associated with poison gas. The Nobel Prize, however, recognised his ammonia research rather than his wartime activities. There are few better examples of the strange moral neutrality of scientific discovery. Chemistry itself had no opinion on whether nitrogen should become fertiliser or explosives, just as chlorine possessed no opinion on whether it should disinfect water or destroy lungs.

After the war, Haber embarked on another extraordinary project. Germany faced enormous reparation payments and Haber began investigating whether gold dissolved in seawater could be extracted economically. Initial calculations suggested that the world’s oceans contained vast quantities of recoverable gold, potentially enough to help Germany pay its debts. Haber established a secret research group and spent years analysing seawater collected from different parts of the world. Unfortunately, the earlier estimates were wrong by approximately a factor of one thousand. There was indeed gold in seawater, but nowhere near enough to make extracting it profitable. Even one of the greatest chemists of his generation could not turn the ocean into a bank account.

During the 1920s Haber returned to scientific research and transformed his Berlin institute into one of the most important scientific centres in Europe. His life then produced perhaps its greatest irony. Haber had spent decades considering himself a loyal German. He had helped feed Germany, helped maintain its ammunition supplies during the First World War and had enthusiastically offered his scientific expertise to the German military. None of this mattered when Adolf Hitler and the Nazis came to power in 1933. According to Nazi racial ideology, Fritz Haber was Jewish.

New laws required Jewish employees to be removed from German institutions. Haber was faced with dismissing members of his own staff and instead resigned his position. The patriot who had once declared that a scientist belonged to his country during wartime discovered that the country to which he had given so much no longer wanted him. He left Germany and spent time at Cambridge University in Britain before considering a position in Palestine. His health, already poor, deteriorated rapidly and he died of heart problems in Basel, Switzerland, on 29 January 1934. He was 65 years old.

There is one final and particularly disturbing footnote to Haber’s story. His institute and scientists associated with him had also worked on hydrogen cyanide pesticides and fumigation methods. This line of pest-control chemistry contributed to the development of products in the Zyklon family. Haber did not create the Holocaust gas chambers and died years before they existed, but a later cyanide-based pesticide, Zyklon B, was eventually used by Nazi Germany to murder people in concentration camps. Some members of Haber’s own extended family would themselves become victims of the Holocaust. It is an extraordinarily grim addition to the life of a Jewish-born scientist who had once devoted himself so completely to Germany.

Fritz Haber is therefore extremely difficult to place neatly into the usual categories of historical heroes and villains. His ammonia synthesis transformed civilisation and remains fundamental to modern agriculture. Without the industrial process developed from his work, feeding the modern global population would be vastly more difficult. Yet he also consciously used his abilities to develop chemical warfare and personally helped introduce poison gas onto the modern battlefield. Neither part of the story cancels out the other.

Perhaps that is why Haber remains such a fascinating figure more than ninety years after his death. The chemistry that made him famous could create fertiliser or explosives, sustain life or help destroy it. Haber himself demonstrated exactly the same contradiction. He was the scientist who discovered how to make bread from the air and then helped turn the air itself into poison.

Few lives demonstrate more clearly that scientific progress and human progress are not always the same thing.