They were sometimes the butt of jokes, the "comical chemical corporals." Officially they were the British Special Brigade, sent to retaliate against German chemical warfare, selected, as one of their members said, almost willy-nilly. "They wanted chemists," a young recruit later recalled, ." . . so I looked up the formula for water and told them it was H2O and I was in."

Although the Brigade itself has received little attention since its disbandment following the war, chemical warfare in World War I has been mythologized, sentimentalized, and vilified. Its image has been distorted by...