An interesting sequel to this is that the use of poison gas in World War I provided an important step in the treatment of cancer — specifically, Leukemia.
Doctors noticed that survivors of the attacks had significantly lower counts of white blood cells. Chemicals based on the formulation of the gas were tried, and one lymphoma patient actually had a remission of the illness.
Although this patient relapsed afterwords, this was an important step in the development of chemotherapeutic agents for cancer.