As the world was introduced to the destructiveness of total war with new technology in World War I, it also became acquainted with one of the most persistent, hidden threats of today--chemical weapons. World War I brought the destruction of almost an entire continent along with longstanding empires. One of the most powerful exhibits of this new devastating capacity was the introduction of chemical weapons in combat. Although there is some indication that arsenic gas was used during the Peloponnesian Wars from the recorded ailments of soldiers after battles, the first recorded use of a chemical weapon occurred at a battle in Ypres, Belgium in 1915. Over 6,000 cylinders of chlorine gas were released on Allied soldiers, who choked to death from the gas. Chlorine gas was not the only chemical agent used in WWI, as the Allies used phosgene later in 1915, and the Germans introduced mustard gas into battle in 1917.
The power of these new weapons prompted the initiation and signature of the Geneva Protocol ("Protocol for the prohibition of the use in war of asphyxiating, poisonous, or other gases, and of bacteriological methods of warfare") in 1925. Despite the prohibition on using such weapons, new and increasingly toxic ones were developed. Prior to and during World War II, Germany developed what are now known collectively as "nerve agents," including sarin, tabun, and soman. Decades later, Great Britain developed another nerve gas--"codename VX"--that is more commonly called VX gas. Another newly developed chemical weapon, Agent Orange, was used by the United States in the Vietnam War. Most recently, Iraq used chemical weapons, including mustard gas and tabun, against native Kurds in the 1980s, and the 1995 Tokyo subway attack by Aum Shinrikyo killed 11 people and injured over 5,000 with sarin gas. Prompted by these revolutions in chemical warfare, the Geneva Protocol branched into separate treaties, one of which, the Chemical Weapons Convention, entered into force in 1997.
What differentiates chemical weapons from the other known identified weapons of mass destruction in the various original forms of the Geneva Protocols--nuclear, biological, and radiological--is both the method by which they are developed and delivered. Neither Germany nor Great Britain intended on developing a chemical weapon when they each created the first novel weapon in their arsenal. Both were in the process of experimenting with insecticides and ended up with a "dual use" weapon--a weapon that serves an additional purpose other than military use (in this case, an insecticide). This is not uncommon for chemical weapons; many of their precursors, even immediate precursors, are commonly used materials in various industries--pharmaceuticals, biotechnology, academia, cosmetics, etc. This also makes delivery of chemical weapons unique; they do not require the immense maintenance or delivery mechanisms of nuclear weapons, nor do they require the stable, habitable conditions of biological agents. It is these unique qualities of chemical weapons that pose the greatest challenge when attempting to prevent their usage in either conventional or unconventional warfare.
There are a multitude of known chemical weapons. In order to assist with enforcement, the Chemical Weapons Convention (CWC) divided the weapons into three "Schedules." The schedules correspond to a measure of toxicity (with Schedule 1 being the most potent) and also the date on which the chemicals were to be monitored with export controls and banned from usage (Schedule 1 being the first). There are eight Schedule 1 chemicals, but three "precursors"--compounds needing only few minor modifications before becoming a chemical toxin--are also included as Schedule 1 chemicals. There are three Schedule 2 chemicals and 11 Schedule 2 precursors, and four Schedule 3 chemicals and 13 Schedule 3 precursors. In addition to the Schedule chemicals, there are also "Unscheduled Discrete Organic Chemicals" (UDOCs) that are to be reported and monitored by export controls under the CWC. …