Answer:
Many nations agreed to stop using chemical weapons after World War I.
Step-by-step explanation:
The use of chemical weapons during World War I had devastating effects on humanity; both on the aggressors and aggrieved. It killed hundreds of thousands and gave many others, after-effects that lasted them decades.
The Chemical Weapons Convention (CWC) control treaty was put into force on 29th April 1997 where production, stockpiling, and use of chemical weapons was outlawed.