THE NIXON DECISION
While US field tests of biological weapons were reaching new heights of realism, political forces were at play that would make all offensive biological weapons programs illegal. The era of legitimate state retaliation in kind, begun by the French in the 1920s, ended with President Nixon's 1969 renunciation of biological weapons for the US and with the 1972 Biological Weapons Convention. By 1975, when the treaty came into force and also when the US finally ratified the Geneva Protocol, comprehensive international legal norms against state programs and the possession or use of biological weapons were in place.
In the United Kingdom this shift away from biological warfare programs began earlier, in 1959, when Porton declared an end to its offensive biological projects in favor of defensive research and development. Having ratified the Geneva Protocol in 1930 and reserved only the right of reprisal, the United Kingdom's adherence to the treaty was an obstacle to integrating either biological or chemical weapons into war plans: why develop weapons that might never be used?1 Compared to nuclear weapons, biological weapons offered little additional as a deterrent. Technically they were untested in war and, despite large-scale simulations, it remained that the likely effects of actual intentional epidemics would be delayed, uncertain, and geographically imprecise. In 1952 the British successfully tested their first atomic bomb, giving the United Kingdom a new level of strategic and deterrent capability. The French, having conducted their first atomic bomb test in the Sahara in i960, were on the same road toward becoming a nuclear power, and their interest in biological warfare was fast waning.