Commentary Nuclear, biological, and chemical (NBC) weapons were considered weapons of mass destruction (WMD) during the Cold War. Later, radiological weapons were generally considered to be another form of WMD. Each of these weapons had a horrific effect: they could kill large numbers of people and so norms prohibiting their use were established and have mostly held. Nuclear weapons have not been used since 1945, and biological weapons not used since the Japanese military’s Unit 731 employed them in China against civilians and other allied prisoners of war during the Second Sino-Japanese War (1937–1945). While chemical weapons were used in Syria’s civil war, there has not been widespread use of chemicals or toxins in interstate warfare since World War I and Italy’s employment in Ethiopia in the Second Italo-Ethiopian War from 1935 to 1936. Despite allegations of their use and their considerable stockpiles, WMD were not used by the superpowers …