Chemical warfare

Chemical warfare. The use of toxic chemical substances as weapons of war constitutes a distinct and particularly feared form of armed conflict. These agents, designed to incapacitate, injure, or kill, have been deployed from ancient conflicts through the industrialized battlefields of the 20th century to contemporary conflicts in the Middle East. The development, deployment, and prohibition of these weapons have profoundly influenced military strategy, international law, and global security paradigms, leading to comprehensive treaties like the Chemical Weapons Convention.

History

The earliest recorded instances involve the use of smoke and incendiaries, such as during the Peloponnesian War when Sparta employed sulfur fumes against Athens. More systematic development began in the 19th century, with proposals during the American Civil War. However, modern chemical warfare is indelibly linked to World War I, where its large-scale use began with the German Empire releasing chlorine gas at the Second Battle of Ypres in 1915. This was followed by the deployment of more lethal agents like phosgene and mustard gas by all major powers, including the British Army and French Third Republic, causing horrific casualties at battles like the Battle of the Somme. The interwar period saw further research, tragically realized in the extensive use of chemical agents by the Kingdom of Italy in the Second Italo-Ethiopian War and most infamously by Nazi Germany in the Holocaust using Zyklon B. During the Cold War, both the United States and the Soviet Union maintained massive stockpiles, while chemical weapons were deployed in the Iran–Iraq War, notably by Saddam Hussein against Kurdish civilians in Halabja.

Agents and classification

Chemical warfare agents are categorized by their primary physiological effects. Blister agents, or vesicants, such as sulfur mustard and lewisite, cause severe skin, eye, and mucosal burns. Nerve agents, like sarin, tabun, soman, and VX, are organophosphorus compounds that disrupt the nervous system, leading to death by asphyxiation. Blood agents, including hydrogen cyanide and cyanogen chloride, interfere with cellular respiration. Choking agents, or pulmonary agents, such as chlorine, phosgene, and diphosgene, damage the respiratory tract. Incapacitating agents, like BZ, are intended to temporarily disable personnel, while riot control agents, including CS gas and pepper spray, are used for crowd control but are banned for warfare under the Chemical Weapons Convention.

Delivery mechanisms

Effective dissemination is critical for chemical weapons. Historically, simple wind-borne release from cylinders was used, as at Ypres. Modern delivery systems are far more sophisticated and include artillery shells, mortar rounds, rockets, and ballistic missiles, which can be fired from systems like the BM-21 Grad. Aerial delivery via bombs or spray tanks from aircraft such as those used by the Iraqi Air Force has been documented. Cruise missiles and unconventional methods, including improvised explosive devices, have also been employed. The design of munitions, such as binary munitions where two less-toxic precursors mix in flight, represents a significant technological development.

Protection and decontamination

Defense against chemical attack requires integrated systems. Personal protection starts with the gas mask or a more comprehensive CBRN suit, pioneered by organizations like the British Royal Engineers. Collective protection involves sealed vehicles and buildings with overpressure systems. Decontamination is a critical and urgent process, using solutions like hypochlorite or specialized powders to neutralize agents on personnel, equipment, and terrain. Rapid detection and identification, using equipment developed by agencies like the United States Army Medical Research Institute of Chemical Defense, are essential for effective response and medical countermeasures, such as atropine auto-injectors for nerve agent poisoning.

International law and treaties

The horrific toll of World War I spurred the first major international effort to ban chemical weapons, the 1925 Geneva Protocol, which prohibited first use but not possession. The cornerstone of modern prohibition is the 1993 Chemical Weapons Convention (CWC), which entered into force in 1997 and is administered by the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague. The CWC comprehensively bans the development, production, stockpiling, and use of chemical weapons and mandates the destruction of existing stockpiles, a process overseen by the OPCW. Other relevant agreements include the Biological Weapons Convention and the Australia Group, an export control regime. Alleged violations, such as those in Syria, are investigated by the OPCW-UN Joint Investigative Mechanism.

Notable incidents and deployments

Beyond the major use in World War I, several incidents stand out. The Imperial Japanese Army used chemical weapons extensively during the Second Sino-Japanese War, with units like Unit 731 conducting horrific experiments. The Vietnam War saw the United States employ defoliants like Agent Orange, which had severe long-term health and environmental consequences. The Soviet Union was accused of using chemical weapons in the Soviet–Afghan War. In the 1990s, the Aum Shinrikyo cult used sarin in the Tokyo subway sarin attack. Most recently, the Syrian Civil War has seen numerous alleged attacks by the Syrian Armed Forces using agents like sarin and chlorine on civilians in locations such as Ghouta and Khan Shaykhun, leading to military strikes by the United States, France, and the United Kingdom.