• Fritz Haber was devastated by his country’s defeat. He feared that he would be tried as a war criminal, and left Germany for Switzerland wearing a fake beard. Haber needn’t have worried. In 1919 he was awarded the Nobel Prize in chemistry instead, for his prewar development of the Haber process. He was restored to respectability, though there were loud protests at the award. Haber himself was anything but contrite and did not avoid the subject of CW when he received the prize, saying: “In no future war will the military be able to ignore poison gas. It is a higher form of killing.”

They were hardly ignoring it. Four classes of agents had been developed during the war and were being refined in the postwar period:

Asphyxiants or “choking agents”, which attacked the lungs and could cause victims to drown in their own lung fluids. The classic agents were chlorine and phosgene, but other agents were used during the war. “Diphosgene” was similar to phosgene in composition and action, but easier to handle. “Chloropicrin”, known as “vomiting gas” by the British, “aquinite” by the French, and “klop” by the Germans, was much less effective than phosgene and had a nasty strong odor that gave away its presence, but it was inert; it could penetrate gas mask filters more easily and was sometimes used in combination with other gases.

Blistering agents, consisting of several different forms of mustard gas. The original German chemical agent was “sulfur mustard”, but after the war “nitrogen mustard” agents were synthesized and manufactured as well. Nitrogen mustard was easier to manufacture and more persistent than sulfur mustard. The Americans did make a significant contribution to CW in the form of a blistering agent named “lewisite”, developed in 1918 by W. Lee Lewis of the Catholic University in Washington DC. Lewisite was similar to mustard gas in its ability to cause damage to a victim’s entire body, but much faster-acting, though apparently it degraded easily when it came into contact with water.

Lewisite was an oily liquid that ranged from clear to dark colored, depending on impurities. Pure product had little smell, but impure product smelled something like geraniums. It was an arsenic-based or “arsenical” compound that caused a burning sensation on the skin within about 15 seconds. The Americans built a huge production facility at Edgewood Arsenal to manufacture lewisite in quantity. It was too late in the war to get it into service and the Americans blessedly gave up its production soon after the end of the conflict. However, they had let the genie out of the bottle and other nations would find lewisite very interesting.

A family of other broad-effect irritants were developed in the postwar period as well, known as “nettle gases” since they made a victim feel as if he had been dragged through stinging nettles. The best-known of the nettle gases was “phosgene oxime”. The name is somewhat misleading since it had no strong chemical relationship to phosgene, and of course had a much different action.

Blood agents, most specifically aqueous “hydrogen cyanide (HCN)”, also known as “prussic acid” or “hydrocyanic acid”, which blocked the absorption of oxygen in the blood. Cyanides had been used in combat by the Allies to an extent, but though deadly in enclosed spaces, they tended to dissipate quickly in open air, and they had little useful effect in low concentrations.

A wide range of “nonlethal”, or more correctly “less lethal”, gases, including tear gases and vomiting agents. Such substances are now known as “riot control agents (RCAs)”. Many different tear gases were used during World War I, such as “chloracetone” and “bromacetone”, and after the war new tear gases were developed, including “chloracetophenone (CN)” and “ortho-chlorobenzylidene malononitrile” — the second being an aerosol powder mercifully better known as “CS” after its inventors, Corson and Stoughton. CN is actually the basis of the popular self-defense spray known as “Mace”, and CS remains in use by the US military as an RCA and for gas training. By the way, modern “pepper spray” is actually based on a substance named “capsaicin” that is the active ingredient of chili peppers. One of the best-known vomiting agents was “adamsite” or “DM”, an arsenical like lewisite. Vomiting agents tended to be more lethal than tear gases and they were eventually abandoned.
Incidentally, the term “chemical weapon” does not mean a poison gas in itself. It formally means a weapon used to deliver poison gas, such as a shell or a gas cylinder. The poison gases are formally referred to as “chemical agents”.
Rumors linger that gas warfare continued in the confused years immediately after WWI, if on a very small and quiet scale. Gas shells may have been used in the Russian Civil War by both the White and Red armies, and may have been used by colonial powers on occasion to help suppress rebellious populations.
Fritz Haber continued his work on poison gases under the cover of “pest control”, since gas weapons had been forbidden to the Germans by the Treaty of Versailles in 1919. Haber developed an insecticide that could be used to fumigate buildings, in the form of a crystalline material that released hydrogen cyanide fumes. It could also be deadly to humans in enclosed spaces. It was known by the tradename of “Zyklon B”, and the Nazis would find it a useful substance for their extermination camps 20 years later. Although hydrogen cyanide was a poor battlefield agent, it would almost certainly end up killing more people than all other poison gases ever used.

  • If gas warfare continued in secret, in public it was made illegal through a series of international treaties that culminated in the Geneva Protocol of 1925. 38 countries signed the protocol, renouncing the use of chemical weapons, though the treaty was not ratified by the US and Japan.

There were major loopholes in the treaty; it had few or no verification or enforcement clauses; and the major powers continued to develop chemical weapons in secret. During the late 1920s, the Soviets began to develop their own gas warfare capability with cooperation from Weimar Germany, and in the same timeframe the Japanese obtained their own gas warfare capability. The Japanese were industrious in their chemical weapons efforts, producing mustard gas and lewisite; chemical bombs, rockets, aerial dispensers, anti-tank grenades using hydrogen cyanide charges, and other weapons; and chemical protection gear not only for men, but for horses, camels, and dogs.

When the Nazis came to power in Germany in 1933, they were very interested in gas warfare. Hitler had been impressed by its capabilities after his incapacitation by a gas attack, and in the form of Fritz Haber, Germany possessed a great resource for chemical warfare. However, Haber’s Jewish background made him distasteful to the Nazis. His stature was such that he was told he could remain in charge of his research, but that all his Jewish workers must resign. He replied that he would resign as well. He left Germany, and died in Switzerland the next year, in 1934. His instructions indicated that he was to be buried next to Clara.