By the end of WWI, scientists working for both warring parties had evaluated some 3,000 different chemicals for use as weapons. Even though poison gas didn’t end up becoming an efficient killing weapon on WWI battlefields—it was responsible for less than 1% of WWI’s fatalities--its adoption set a precedent for using chemicals to murder en masse. In the past century, poison gas has killed millions of civilians around the world: commuters on the Tokyo subway, antigovernment demonstrators in Syria, and those incarcerated in Third Reich concentration camps. Everts profiles chemist Fritz Haber, the man who lobbied to unleash the gas that day in 1915."
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