ironic

He, though, was a converted Jew and loyal above all else to his country. He pushed the military into the use of chemical weapons. Their first major trial, of chlorine gas against French troops at Ypres on April 22, 1915, was a stunning success. Five thousand were killed and another few thousand incapacitated.

The German papers were full of praise, and Haber was promoted to captain. Finally a way had been found to break the stalemate of trench warfare. Haber threw a dinner party to celebrate. Clara and he got into a furious argument. That night she took his army pistol and killed herself in their garden with a shot to the chest.

Haber left the next day for the Eastern front, not even staying for the funeral arrangements. He continued to promote the use of poison gases, even when the true answer to the trenches turned out to be tanks. He was branded a war criminal after the Allied victory, but still won the Nobel Prize in 1918 for ammonia synthesis.

He remarried, and spent the years after war doing basic chemistry, but also searching desperately for a way to extract gold from seawater in order to pay the Weimar's Republic's debts. He rose steadily in honors, but nothing availed him when the Nazis came to power. Converting to Christianity and aiding one's country mightily in its worst struggle didn't count compared to his ancestry.

also:

In the 1920s, scientists working at his institute developed the cyanide gas formulation Zyklon B, which was used as an insecticide, especially as a fumigant in grain stores, and also later in the Nazi extermination camps. [...] He committed suicide in 1946. Members of Haber's extended family died in concentration camps through the use of his invention, Zyklon B.