Germans introduce poison gas

Certainly gas was used by the Germans against the Jews but I guess that doesn't count?

Also Japan had used biological warfare agents against the Chinese during 1940 and killed over 500,000 civilians in that manner. Japan's unit 731, a Biological Warfare unit was responsible and had even built 14 foot high fence to keep people contained so they couldn't escape death. There were Six separate attacks using biological agents developed by Japan. In addition to the biologic agents they also tested poison gases on Prisoners. General Shiro Ishii of Japan headed up the development of both the Biologic and also poison gas and not only wasn't prosecute as a War Criminal but instead it was covered up so He could help the US develop things such as both Chemical. biological and poison gas including mustard gas in the post WWII era. This information was used by the US Army Chemical Corps and some of these thing stockpiled by them. Many of those Japanese scientist involved in that went and then worked for the United States.

All of that was mentioned in the Article. I agree with the article, the biggest reason that it hasn't been used against conventional forces is that modern armies are prepared and it just tends to piss people off and can lead to some unwanted escalation.

Lt Col Charlie Brown oh it definitely counts.