sentences:  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.