A blistering agent that gives off an odor often compared to garlic or horseradish, sulfur mustard (as it is also known) damages the skin, eyes and lungs. Its effects are delayed, meaning many soldiers initially had little idea they had been exposed.
Within hours of its use, dressing stations were overwhelmed by more than 2,000 casualties suffering agonizing chemical burns. Many were temporarily blinded, while others struggled to breathe as the gas ravaged their airways.
Over the following weeks, roughly a million mustard gas shells fell around the Ypres salient, leaving thousands disfigured or permanently disabled. By autumn, mustard gas was being used across the Western Front and would remain a feature of the war until the Armistice.
For a brief history of mustard gas, visit: militaryhistorynow.com/2014/…


