Dr. James S. Ketchum, an Army psychiatrist who in the 1960s conducted experiments with LSD and other powerful hallucinogens using volunteer soldiers as test subjects in secret research on chemical agents that might incapacitate the minds of battlefield adversaries, died on May 27 at his home in Peoria, Ariz. He was 87.

His wife, Judy Ketchum, confirmed the death on Monday, adding that the cause had not been determined.

Decades before a convention eventually signed by more than 190 nations outlawed chemical weapons, Dr. Ketchum argued that recreational drugs favored by the counterculture could be used humanely to befuddle small units of enemy troops, and that a psychedelic “cloud of confusion” could stupefy whole battlefield regiments more ethically than the lethal explosions and flying steel of conventional weapons.

For nearly a decade he spearheaded these studies at Edgewood Arsenal, a secluded Army chemical weapons center on Chesapeake Bay near Baltimore, where thousands of soldiers were drugged.