Army researchers studying chemical weapons administered a variety of illicit drugs to volunteer soldiers over nearly a 20-year period, according to a new book.

USA Today reported April 6 that a program at the Army's Edgewood, Md., arsenal tested synthetic marijuana, LSD, and two dozen other drugs on soldiers between 1955 and 1972. The studies led to the development of a chemical weapon called quinuclidinyl benzilate or BZ, which can be loaded into an artillery shell and causes victims to hallucinate and fall into a sleeplike state.

Psychiatrist James Ketchum memoir about working at the Edgewood facility is the first insider's account of the program, which was acknowledged by the military in the 1970s. Ketchum urged the military to revisit research on incapacitating agents to fight terrorists. But such research would be illegal under current international law, experts said.

Ketchum wrote that LSD was rejected as a weapon because victims could still act violently, while marijuana was not strong enough to incapacitate enemy soldiers.