When we discuss weapons of mass destruction, chemical warfare ranks as one of the most destructive ever created. It is the use of toxic chemical substances as weapons. Chemical warfare is not the same thing as biological, radiological and nuclear warfare, but it is in the same category as them as weapons of mass destruction. The destructive effects of chemical warfare come not from its explosive impacts. It is using toxic non-living products which may be developed in the laboratory or produced by a living organism is considered to be chemical warfare. According to the Chemical Weapons Convention, chemical weapons cover all toxic chemicals regardless of the origins unless such materials are used for purposes that are not restricted.
Chemical warfare is not a 21st-century phenomenon; it is something that has been happening for a long time. The Industrial Age and even Antiquity are filled with multiple instances where simple chemical weapons were used. However, the 19th century saw the development of chemical warfare as a modern concept with various nations and scientists recommending that poisonous or asphyxiating gases be used.
This led to several international treaties that banned the use of such weapons. However, this did not prevent its use in the First World War where the two sides used chlorine gas and other chemicals at war. While it was not very effective, it had some impacts on the war and instead of killing victims, usually maimed, disfigured, and injured casualties in the worst way possible.
Fritz Haber is believed by many to be the father of chemical warfare as he pioneered the weaponing of various poisonous gases, including chlorine during the war. There was the occasional use of chemicals with Nazi Germany carrying out substantial research into the work even though they did not apply that research later on in the war.
Since the World Wars ended, there has been significant use of chemical warfare as seen in the United States military use in the Vietnam war, the use in the Iran-Iraq war, Syrian civil war, among others. Even terrorists have made use of these chemical weapons as seen in the Matsumoto incident.
There are around 70 chemicals stockpiled or used as chemical warfare agents. These chemicals come in all forms of matter, and they are classified into incapacitating and lethal. Chemicals are classified as incapacitating if 1/100 of their lethal dose can lead to incapacitation. Beyond this, the difference between the two is not fixed. The persistency of the chemical is another factor used for classifying them. This is how long the chemical will last, and the ones that will last most are considered persistent. The mode of delivery, dispersion, etc., also represents features used in classification.
Treaties are in place to prevent the use of these chemicals with various sanctions in place against those who use it. Regardless of this, personal protection is also necessary, and this comes in multiple forms such as gas masks, decontamination, etc.