Prior to the atomic bomb’s invention, it was described as “the most terrible instrument of manslaughter ever conceived… a drop on the hand would cause intolerable agony and death after a few hours.”

At the time it was called methyl, now referred to as Lewsite. It was first synthesized in 1904, but production ramped up in 1918 for WWI. Luckily, it was never deployed in that conflict — saved by the bell:

The signing of the armistice spared the enemy any first-hand acquaintance with the terrors of methyl. Major Gen. W.K. Sibert, in command of the Chemical Warfare Service, had directed that 3,000 tons of it, in shell and drums, be in readiness on the battlefield March 1, 1919. Ten tons a day were being produced in an eleven-acre plant near Cleveland, Ohio, and the plant was two months ahead of its schedule when Foch crossed No Man’s Land to offer terms to a beaten foe. It is estimated that ten tons of methyl is one ton more than enough to depopulate Manhattan Island; and so it is not difficult to guess what would have happened had Hindenburg and his cohorts persisted until Spring.

1997’s Chemical Weapons Convention banned the production or stockpiling of Lewisite. In 2012, the U.S. destroyed its final remnants of its Lewisite stockpile. At least 98% of the stockpiles have been destroyed globally.

Our Super-Poison Gas: First Story of Compound 72 Times Deadlier Than “Mustard,” Manufactured Secretly by the Thousands of Tons

Published: Sunday, April 20, 1919