Chemical Warfare

The first large-scale use of poisonous chemicals in warfare occurred during World War I. More than 100,000 tons (90,700 metric tons) of lethal chemicals were used by both sides during several battles in an effort to break the stalemate of endless trench warfare. The most commonly used chemicals were four lung-destroying poisons: chlorine, chloropicrin, phosgene, and trichloromethyl chloroformate, along with a skin-blistering agent known as mustard gas, or bis (2-chloroethyl) sulfide. These poisons caused about 100,000 deaths and another 1.2 million injuries, almost all of which involved military personnel.

Despite the agreements of the Geneva Protocol of 1925 to ban the use of most chemical weapons, the United States, Britain, Japan, Germany, Russia and other countries all continued development of these weapons during the period between World War I and World War
II. This development included experimentation on animals and humans. Although there was only limited use of chemical weapons during World War II, the opposing sides had large stockpiles ready to deploy against military and civilian targets.

During the war in Vietnam, the United States military used a nonlethal "harassing agent" during many operations. About 9,000 tons (8,167 tonnes) of tear gas, known as CS or o-chlorobenzolmalononitrile, were sprayed over 2.5 million acres (1.0 million ha) of South Vietnam, rendering the areas uninhabitable for 15-45 days. Although CS is classified as nonlethal, several hundred deaths have been reported in cases when CS has been used in heavy concentrations in confined spaces such as underground bunkers and bomb shelters.

Poisonous chemicals were also used during the Iran-Iraq War of 1981-1987, especially by Iraqi forces. During that war, both soldiers and civilians were targets of chemical weapons. Perhaps the most famous incident was the gassing of Halabja, a town in northern Iraq that had been overrun by Iranian-supported Kurds. The Iraqi military attacked Halabja with two rapidly acting neurotoxins, known as sabin and tabun, which cause rapid death by interfering with the transmission of nerve impulses. About 5,000 people, mostly civilians, were killed in this incident.