The United States biological weapons program officially began in spring 1943 on orders from U.S. President Franklin D. Roosevelt. Research continued following World War II as the U.S. built up a large stockpile of biological agents and weapons. Over the course of its 27-year history, the program weaponized and stockpiled seven bio-agents — Bacillus anthracis (anthrax), Francisella tularensis (tularemia), Brucella spp (brucellosis), Coxiella burnetii (Q-fever), Venezuelan equine encephalitis virus, Botulinum toxin (botulism), and Staphylococcal enterotoxin B. The US also pursued basic research on many more bio-agents. Throughout its history, the U.S. bioweapons program was secret. It was later revealed that laboratory and field testing (some of the latter using simulants on non-consenting individuals) had been common. The official policy of the United States was first to deter the use of bio-weapons against U.S. forces and secondarily to retaliate if deterrence failed.
In 1969, President Richard Nixon ended all offensive (i.e., non-defensive) aspects of the U.S. bio-weapons program. In 1975 the U.S. ratified both the 1925 Geneva Protocol and the 1972 Biological Weapons Convention (BWC)—international treaties outlawing biological warfare.