The life of Fritz Haber is also the story of the glory of German chemistry. In his time, German chemistry and physics dominated the world’s science, and Haber was one of its most celebrated and honored scientists. He was born in Breslau in 1868, son of cousins Siegfried Haber and Paula Haber. Fritz’s mother died of complications of his birth, and Fritz was raised by Siegfried’s second wife, with important contributions from aunts and uncles. Fritz’s uncle Hermann, who was active in politics and managing director of a newspaper in Breslau, apparently provided a place for Fritz to carry out some chemical experiments while he was a young teenager. Haber credited him with convincing his father that the study of chemistry would be acceptable. Fritz decided to study first at the Friedrich Wilhelm University in Berlin because of the reputations of its director, August Wilhelm von Hoffmann and the physicist Hermann von Helmholtz. However, both of those men were over 60 by that time—clearly too old to be good for anything. Haber was not very satisfied with his time in Berlin, and the famous name of Robert Bunsen attracted him to Heidelberg, where he spent the summer semester of 1887. After a year of “voluntary” service in the Field Artillery (which was required by law, so how voluntary was that?), Haber returned to Berlin. He became a graduate student of Carl Liebermann, with whom he studied the organic chemistry of dyes and completed his Ph.D. in 1891.

Haber’s glory years were the 17 that he spent at Karlsruhe, first in the institute run by Hans Bunte as a research associate, then as the equivalent of an assistant and associate professor, and later as professor and director of the Karlsruhe Institute of Technology. In 1920, this included about 65 professors, docents, unpaid assistants (hard to find these days), and doctoral students.

During this time, Haber married the first of his two wives, an accomplished chemist (and quite a beauty) named Clara Immerwahr. They were married as Christians, even though both had come from Jewish families. Haber had converted a few years earlier, and he pressured his fiancé to do so, too. It was at Karlsruhe that Haber accomplished the scientific work that made him famous. The ammonia synthesis was a triumph of imagination and technology. Previous attempts to “fix” nitrogen from the atmosphere had nearly all attempted to do so by oxidizing the element (usually in a combustion reaction of some kind). Haber was eventually successful by going in the opposite direction—by reducing it with hydrogen. As I have taught about this process, I have always assumed that the specified catalyst, iron, was a compromise because platinum and palladium were too expensive. As it happens, iron is far better than any other substance, and this was discovered by Haber through painstaking trial-and-error. A young chemical engineer named Carl Bosch was responsible for scaling up the reaction from laboratory to industrial size, and the process is properly called the Haber–Bosch process in recognition of his essential and significant contribution to the challenges, not only making ammonia from nitrogen and hydrogen, but also producing the hydrogen gas reagent in industrial quantities.

One could argue that fixation of nitrogen from the atmosphere is and was the most important chemical reaction in history, as it is essential for the practice of modern agriculture. Without it, it would not be possible to sustain the present human population of the planet. The significance of this development was recognized immediately in Germany, and led to Haber’s appointment as Director of the newly established Kaiser Wilhelm Institute, which he began to administer in 1911.

Haber was a German patriot, who put the resources of his Institute at the service of his country during World War I. Synthetic ammonia became the feedstock for explosives and ammunition when Germany’s access to nitrate mines was cut off. It is estimated that Germany would have had to capitulate in 1915, had it not been for the Haber–Bosch process. But Haber did more. He was enthusiastic about the possible uses of gaseous compounds in warfare, first chlorine and later mustard gases. He frequently visited the war front, and personally supervised some of the chemical deployment, including the first such instance in Ypres, France. It was when he returned from this battle that his wife, Clara, committed suicide using Haber’s military sidearm.

The shadow of his involvement with the German military and chemical warfare hung over Haber for the rest of his life, and his award of the Nobel in 1920 was controversial because of that. His star began to set later in his life, not because of his enthusiasm for the military, but because of his Jewish roots. In the 1920s, as probably the foremost German scientist among a constellation of them, Haber was a champion for national investment of society in science and technology, and for the cooperation of scientific societies from many nations. Had it not been for the rise of the Nazis, Haber would probably have ended his life as an honored patriot, but his Jewish heritage (which he increasingly acknowledged after the war) was intolerable to Hitler. Haber died in exile in France in 1934.