Optional Resource: A Century of Chemical Warfare: Building a World Free of Chemical WeaponsWalker, P.F. (2017). A Century of Chemical Warfare: Building a World Free of Chemical Weapons. In Friedrich, B., Hoffmann, D., Renn, J., Schmaltz, F., Wolf, M. (eds) One Hundred Years of Chemical Warfare: Research, Deployment, Consequences. Springer, Cham.The first major use of chemical weapons in warfare was on April 22, 1915, when Germany attacked Allied forces along the Ypres Salient in Belgium in World War I. Since that historic attack a century ago, dozens of countries have researched, developed, tested, and deployed still more deadly chemical weapons. These inhumane and indiscriminate weapons of mass destruction were again used in 1924 by Spain against Morocco, by Italy against Libya and Ethiopia in the 1920s and 1930s, and by Japan against China in World War II (Robinson 1971). More recently they were deployed by Iraq against Iran and Iraq’s Kurdish population in the 1980s, and from 2012 to the present in the Syrian civil war. The 1993 Chemical Weapons Convention (CWC) in 2016 includes 192 countries, 98% of the world’s population, with only four countries—Egypt, Israel, North Korea, and South Sudan—still missing. And of the 72,525 metric tons of chemical agents declared to date in eight possessor states, over 66,000 metric tons—92%—have been safely destroyed in the last 25 years. This is a historic achievement in global disarmament and peacebuilding and needs to continue until we rid the world of all chemical weapons, prevent their re-emergence, and promote peaceful uses of chemistry.