The Germans were the first to employ chemical weapons in WWI, chlorine gas, first used at the Second Battle of Ypres (April, 1915). Then they introduced Mustard gas at the Third Battle of Ypres (July 1917), known to Canadians as Passchendaele, a deadly battle. It seems Ypres was a popular place for deadly things.
As a chemistry teacher I stressed the difference between elements and the compounds they made.
Case in point: chlorine and sodium forming table sale. The elements are deadly. Chlorine gas was used in WWI. It reacts with water in respiratory tract forming hydrochloric acid. This had the added ‘benefit’ of maiming troops who then had to be cared for. Wounded but living soldiers tie up evacuation, medical, and support resources and are a heavier logistical burden than immediate fatalities. This could degrade enemy combat power over time more effectively than a higher immediate kill rate.
Sodium metal reacts violently with water forming explosive hydrogen gas and sodium hydroxide (lye)…oven cleaner. It dissolves you from the inside...if you don't blow up first.
Their product, sodium chloride, table salt, is vital for human life. If you don’t eat it, you die. In sub-Saharan Africa, circa 1300, salt was so valuable that it, at times, traded even up for gold by mass.
Big difference between elements (chlorine and sodium) and their product (salt). Not even close.