http://www.npr.org/2015/09/05/437555125/veterans-used-in-secret-experiments-sue-military-for-answersAmerican service members used in chemical and biological testing have some questions: What exactly were they exposed to? And how is it affecting their health? Tens of thousands of troops were used in testing conducted by the U.S. military between 1922 and 1975. As one Army scientist explained, the military wanted to learn how to induce symptoms such as "fear, panic, hysteria, and hallucinations" in enemy soldiers. Recruitment was done on a volunteer basis, but the details of the testing and associated risks were often withheld from those who signed up.