At the height of morning rush hour on March 20, 1995, terrorists stationed on the trains of three Tokyo subway lines used umbrella tips to puncture plastic bags filled with sarin gas—a deadly chemical developed by the Nazis during World War II. As the gas dispersed, thousands of passengers staggered out onto the street, some with headaches and chest pains, others bleeding from the nose or vomiting uncontrollably. The attack, which left twelve people dead and over 5,000 injured, was attributed to the fanatical Buddhist cult Aum Shinrikyo.

Some commentators claim that the Aum Shinrikyo attack has wide-reaching implications about the likelihood of chemical or biological terrorism. According to Jonathan B. Tucker, the Director for Chemical and Biological Weapons Proliferation Issues at the Center for Nonproliferation Studies, “As the first large-scale terrorist incident involving a lethal...