The concept of using chemicals for acts of poisoning is very ancient. These were usually acts against single individuals or small groups by oral administration, but the use of chemicals on a mass scale as incendiary weapons is recorded in the wars of classical Greece, probably first during the Peloponnese War when the Spartans set fire to woods drenched in sulphur and pitch (‘Greek Fire’) to force the surrender of cities under siege. Choking fumes would have been part of the problem for the defenders. However, using the toxicity of a chemical as a mass weapon did not become regular practice until World War I, when the infamous ‘official’ first use of what henceforth became known as ‘chemical weapons’ was the use of chlorine gas by the German troops at Ypres in Belgium on April 22nd, 1915. Subsequently, both the Axis powers and the Allied developed and used different ‘poison gas’ agents, including chlorine, phosgene and mustard. The chemicals were either existing industrial chemicals or chemicals that could easily be made by industrial processes. The original delivery method of opening canisters of gas and letting the wind blow the gas to enemy lines was replaced by the use of artillery shells. The toxic chemicals chosen had physical properties that allowed them to arrive at the target either as fine droplets or a gas that could act through the lungs, eyes or skin. During the interwar period, chemical weapons were used by Spain (in Morocco) and Italy (in Ethiopia) and new, more complex agents were developed, most importantly the nerve agents, developed by German scientists developed these during the 1930s. By the end of World War II, Germany had produced almost 12.000 metric tons of nerve agents. However, neither Germany nor the Allied forces used chemical weapons during World War II. Iraq was the next (and last) state actor to use chemical weapons: first in its war against Iran and later against its own Kurdish population, most notoriously the Halabja poison gas attack on March 16th, 1988.
The Chemical Weapons Convention
In 1993 chemical weapons were banned by the Chemical Weapons Convention, which came into force in 1997. The Convention requires the destruction of stocks of (toxic) chemical weapons, which by then were only held by a handful of the new States Parties but in some cases were on a very large scale- tens of thousands of tonnes in the US and Russia. The OPCW (Organization for the Prohibition of Chemical Weapons) is the international organisation, based in The Hague, or the implementing body of the Chemical Weapons Convention (CWC or Convention). The OPCW is given the mandate to achieve the object and purpose of the Convention, to ensure the implementation of its provisions, including those for international verification of compliance with it, and to provide a forum for consultation and cooperation among States Parties. The vast majority of countries in the world has either signed or ratified the Convention. Israel and Myanmar have signed the CWC, but have not yet ratified it, while Somalia, Angola, North Korea, Syria and Egypt have not yet signed.Now that most states have ratified the CWC, use of chemical weapons by terrorist groups is of utmost concern. The most infamous use of a chemical agent by a terrorist group is the 1995 attack on the Tokyo subway. The religious fundamentalist group Aum Shinrikyo released the highly toxic sarin into the subway system, killing 12, severely wounding 50 and leaving another 1,000 people with temporary vision problems. Since then, it is believed that many more terrorist groups have tried to obtain chemical devices. Chemical weapons can be conveniently divided into five categories: nerve agents, blister agents, choking agents, blood agents and incapacitating agents.
For more information on any of these categories, you can access one of the links on the left.