The concept of "humane warfare" with widespread use of incapacitating or deleriant drugs such as LSD or Agent BZ to stun an enemy, capture them alive, or separate friend from foe had been available in locations such as Berlin since the 1950s, an initial focus of US CBW development was the offensive use of diseases, drugs, and substances that could completely incapacitate an enemy for several days with some lesser possibility of death using a variety of chemical, biological, radiological, or toxin agents. The US Army Assistant Chief of Staff for Intelligence (ACSI) authorized operational field testing of LSD in interrogations in the early 1960s. The first field tests were conducted in Europe by an Army Special Purpose Team (SPT) during May to August 1961 in tests known as Project THIRD CHANCE. The second series of field tests, Project DERBY HAT, were conducted by an Army Special Purpose Team in the Far East during August to November 1962.