I have just finished reading How to Hide an Empire by historian Daniel Immerwahr. It is an excellent book about the complex relationship of the US with the concept of empire and the great lengths it has gone to hide the fact that it is an imperial power. In the early part (p. 56-58) he recounts a poignant story. He tells it so well that to summarize and paraphrase it would be to do a disservice to the story so I give it below.

He sets it up by saying that industrialized agricultural practices had greatly depleted the soil and up to the beginning of the 20th century, the main sources of fertilizer to revive soils were natural sources that were mined from rocky islands in the Pacific ocean that were made of out of hardened bird droppings called guano.

Guano didn’t solve the soil exhaustion crisis, but combined with Chilean sodium nitrates, which companies started selling later in the century, it held it at bay. Mined fertilizers kept industrial agriculture sustainable long enough for scientists to devise a more permanent solution: manufacturing fertilizer from the unreactive N₂ in the atmosphere.

The breakthrough came in 1909 when Fritz Haber, a German-Jewish chemist developed a technique for synthesizing ammonia, a nitrogen compound. By 1914, the experimental technique had become industrially viable, and in that year Haber’s method, called the Haber-Bosch process, yielded as much reactive nitrogen as the entire Peruvian guano trade. The difference was that Haber-Bosch, unlike guano mining, was infinitely expandable. It also didn’t require scouring the seas for uninhabited islands.

In a single stroke, Haber had opened the floodgates for the virtually unlimited growth of human life. The Malthusian logic was repealed. Soil exhaustion ceased to be an existential threat; you could just add more chemicals. Without Haber-Bosch, the earth could sustain, at present rates of consumption, only about 2.4 billion people. That is well under half of today’s population.

By inventing ammonia synthesis, Fritz Haber became arguably the single most consequential organism on the planet. The toll on his personal life, however, was heavy. His wife, Clara, was herself a promising German-Jewish chemist, indeed the first woman ever to receive a doctorate from the University of Breslau. Local women had crowded there to see her get her degree – “seldom has the awarding of a doctorate been attended by so many,” reported the newspaper. But after her marriage, Clara had abandoned her research and become a hausfrau, dedicating her life to support Fritz.

It was a Picture of Dorian Gray marriage: the more Fritz flourished, the more Clara withered. Just as her husband was honing his invention, Clara wrote an anguished letter to her former scientific mentor: “What Fritz has gained in these last eight years, that-and even more-I have lost, and what is left of me fills with the deepest dissatisfaction.”

Fritz had gained quite a lot. His invention won him the directorship of a new institute in Berlin and a central place within the German scientific establishment (a position he used to promote the career of a gifted young physicist named Albert Einstein). When World War I erupted, Haber volunteered his services. He suggested that the ammonia now pouring out of German fertilizer plants could be repurposed as explosives to bolster Germany’s dwindling munitions supplies. Since the war had cut Germany off from imported nitrates, this was an essential contribution. The president of the American Chemical Society calculated that Germany would have lost the war by early 1916 had Haber not replenished its stocks of nitrate explosives.

Nor did Haber stop there. He assembled a supergroup of German scientists, four of whom, like he, would go on to win Nobel Prizes. Overseeing their efforts, he introduced his second great invention: poison gas.

Not only did Haber invent it, he personally supervised its debut in 1915, releasing four hundred thousand tons of chlorine gas upwind of some Algerian troops at the Battle of Ypres. In a delicious historical irony, the man who saved the world from starvation was also the father of weapons of mass destruction.

For this, Haber won still more honors: a military commission, the Iron Cross, and an audience with the emperor. The only one who didn’t appear to be celebrating was Clara. Right after gassing the Algerians at Ypres Fritz returned home for a quick visit. What transpired between husband and wife during that visit is lost to history, but after Fritz went to sleep Clara went into the garden with his service revolver and shot herself in the heart. The next day, Fritz returned to the front.

There is great interest in Clara today, especially in Germany, where she is celebrated as a martyr to science. No note from Clara survives, and Fritz refused to speak about the subject, so it is impossible to say with certainty why she killed herself. Surely, she had many reasons. But the timing of her suicide and some of the testimony from those who knew her have led many to interpret it as a protest of her husband’s invention.

If it was, it was a prescient act. After the war, Fritz continued his work, and his institute developed a promising insecticide called Zyklon A. In slightly modified form, under the name Zyklon B, it would be deployed on Fritz and Clara’s fellow Jews, though this time not on the battlefield, but in gas chambers. Clara’s relatives were among those who died in the camps.

Luckily, not all of them perished. Although Clara’s married name was Haber, she is today known by her maiden name, the name under which she defended her dissertation: Clara Immerwahr.

Her cousin Max was my great-grandfather.

It is a cautionary tale about a problem that all scientists grapple with. Most of them want their work to benefit humankind but at the back of their minds is the awareness that even if the intent was benign, it can also be used for evil and destructive purposes and that once the results of the research is out of our hands, we have no control over how it will be used and that it will sometimes come back and be used against us. Our hands are never clean.