Military and political leaders have worried about large-scale biological warfare for more than a century. “Blight to destroy crops, Anthrax to slay horses and cattle, Plague to poison not armies only but whole districts—such are the lines along which military science is remorselessly advancing,” Winston Churchill lamented in 1925. But despite the deadly potential of biological weapons, their actual use remains rare and (mostly) small scale. Over the last several decades, most states have given up their programs. Today, no country is openly pursuing biological weapons. Read more.