With the recent international attention to riot control agents (RCA) people have raised the question how their use against protesting civilians can be legal when the toxic agents are internationally banned from battlefields.

Framed as such, the question is not entirely correct. In my previous blog posting I argued that outlawing RCAs for law enforcement and riot control based on the above reasoning may run into complications in the United States because the country still identifies operational military roles for irritants on the battlefield in contravention of the Chemical Weapons Convention.

This article sketches the convoluted history of harassing agents as a means of combat and a police tool. For hundreds of centuries until the late Middle Ages irritants were part of siege warfare. In the 19th century interest returned because of a new competition between defensive structures and breaching weaponry. Just like in earlier times, toxic fumes could drive defenders from their enclosed positions. The rise of chemistry introduced new compounds with the potential to clear occupants from fortifications.

Just before World War 1 French police had to confront a new form of gangsterism. Bandits used the most advanced weaponry and tools not yet available to police officers, they barricaded themselves in buildings, and resisted arrest until their last bullet. To reduce bloodshed, the police investigated alternatives to dislodge the new creed of brigands.

From a few thousand years ago…

Siege warfare began as soon as settlers erected permanent physical barriers to protect themselves from roving nomads and nascent expansionist civilisations. For thousands of years, offensive and defensive strategies competed, as did fortifications and weaponry for breaching such defences. Gunpowder and big cannon finally rendered castle and city walls obsolete during the 15th century. While military historians tend to dwell on big siege machinery and engineering designs of defensive structures, tunnelling and scaling ladders remained the most prominent beleaguering techniques until the dawn of the Early Modern Times.

Tunnelling had two main purposes: undermining of massive walls to collapse them and infiltrating troops. Already in early Antiquity tunnelling was met with counter-tunnelling. Not seldom defenders generated irritant smokes to drive out the attackers; sometimes, they used more toxic fumes such as sulphur. Underground combat was deadly, especially if the attackers could not quickly retreat to open air. Meanwhile attackers might lob stinkpots and projectiles filled with putrid matter over walls to force defenders to abandon their positions. Irritants agents to harass enemy troops or clear them from enclosed spaces have been part of warfare for at least a few thousands of years.

A resurgence of interest in the 19th century

The rise of chemistry as a science from the final quarter of the 18th century through the 19th century led to the discovery of many new chemical compounds. Several of the deadliest agents used in World War 1 were first synthesised in the early 1800s. Meanwhile, new types of fortifications arose that contemporary artillery could not easily defeat. This was especially true for shipborne guns taking on coastal defences. Furthermore, empires whose frontiers stretched far beyond the borders of the home country dispatched relatively small expeditionary forces to safeguard their economic and geopolitical interests abroad or engage enemy soldieries as an extension of campaigns fought in Europe. The new forts proved as good as impenetrable and exhausting sieges depleted troops. The beleaguering of Sevastopol (1854–1855) during the Crimean War (1853–1856), for example, eventually cost the British, French, Ottomans and Russians over 100,000 combat fatalities, losses to disease, and other casualties. During the American Civil War (1861-1865) similar proposals emerged, including the fumigation of peppers to generate powerful irritants.

While chemists were not thinking of warfare, some military men embracing science took interest in the new toxic substances, poisonous and irritant smokes in particular, to neutralise the occupants of fortifications. While they undertook some small-scale experiments, their ideas failed to generate enthusiasm among politicians and military leadership.

A first limitation on modern chemical warfare

In the 1860s legal experts and diplomacy started codifying the customs of war to draw up internationally binding agreements. The Crimean War had confronted Russia, then mostly an agrarian society, with the new technologies and power projecting capacities made possible by the scientific and industrial revolution in western Europe. Chemistry ignited and drove the second industrial revolution during the latter half of the 19th century. With it came market dominance through the dye industry, better explosives, higher quality materials (including iron and steel), improved production processes, and faster naval and land transportation.

The second industrial revolution helped to redefine military power. In response, Russia called for an international conference to limit the impact of industrialisation on war fighting. Failing to achieve that, the 1899 Hague Peace Conference adopted the first internationally binding Laws of War. However, one Russian initiative met with some success.

Among the adopted documents was the Declaration (IV,2) Concerning Asphyxiating Gases, whereby

The Contracting Powers agree to abstain from the use of projectiles the object of which is the diffusion of asphyxiating or deleterious gases.

The present Declaration is only binding on the contracting Powers in the case of a war between two or more of them.

It shall cease to be binding from the time when, in a war between the contracting Powers, one of the belligerents shall be joined by a non-contracting Power.

The agreement proved controversial. The USA refused to sign it because it restricted the use of a weapon not yet in existence and consequently it was impossible to judge whether it was more or less humane than other means of warfare. Great Britain also did not sign up due to the lack of unanimity but reversed its stance and became a party at the 1907 Hague Peace Conference.

Notwithstanding, the Declaration was to unintentionally separate what we know today as non-lethal chemical agents from more deadly chemical weapons.

New gangsterism

Between December 1911 and May 1912, a notorious French criminal organisation with ties to the anarchist movement known as the Bonnot Gang committed several murderous robberies. On 28 April 1912, police and the local population encircled an isolated house near Choisy-le-Roi, a hub of the anarchist movement. Jules Bonnot, wounded in a skirmish four days earlier, had sought refuge there. Assisted by the local population, over 500 people eventually beleaguered the building. With Bonnot firing at anybody who moved, the police suffered casualties during the day. Paris Police Chief Louis Lépine took command of the operation and decided to dislodge Bonnot with explosives. After three failed attempts during the late morning, the police finally dynamited the house. Having been hit by 11 bullets, Bonnot succumbed to his injuries shortly after his capture.

Two weeks later, on 14 May, the police surrounded a pavilion in Nogent-sur-Marne where several of the remaining gang members had sought refuge. They had prepared the building for a long siege. Again, the police tried to overcome the resistance by blowing up the structure, but several attempts failed. It ultimately took an assault by police officers and military units at 2 a.m. before the occupants were killed.

Both sieges involved hundreds of police officers, gendarmes and soldiers and witnessed intense, lengthy and deadly exchanges of fire involving repeating weapons by the gang members and military machine guns.

Neither asphyxiating nor deleterious

Faced with the reality that the French police was underarmed and outgunned by new types of gangsters, Lépine looked for alternatives. According to a chronology prepared by Serge Kastell (‘La brigade des gaz. Bande à Lépine contre bande à Bonnot’, Histoire mondiale des conflits, no. 11, December 2002 – January 2004, pp. 20–25), on 29 April, the day after the siege at Choisy-le-Roi, he instructed the Municipal Laboratory of Paris to find a chemical substance allowing ‘to neutralise entrenched criminals in a gentle manner’. He also used dynamite in Nogent-sur-Marne two weeks later because of, so he explained, the narcotic effects of the gases released during the explosion.

Rattled by the turn both sieges had taken, Lépine’s interest in chemical substances and other siege tools followed from the strong desire to protect his officers and to capture rather than kill the gangsters. He established a special civil-military commission to investigate ways how to dislodge barricaded criminals on 26 May 1912. The director of the Laboratoire Central de la Préfecture de Police, André Kling, commission member, proposed on the advice of his assistant Professor Daniel Florentin ethyl bromoacetate as an effective chemical agent devoid of ‘asphyxiating or deleterious’ properties. The commission recommended three tools for police intervention units, namely a gas alternatively labelled ‘smothering’ (suffocant) or ‘narcotic’, a breastplate and a shield. Approval of the chemical followed initial testing first on animals and then on volunteers in the summer. Ethyl bromoacetate had little effect in open air. In closed spaces exposed persons experienced a sensation of suffocation and intense tearing that prevents opening of the eyelids. Dizziness may also ensue.

After the final two official tests in September and October, the police adopted a flare-type of pistol for firing small canisters containing 10–12 cm³ of ‘smothering’ agent against barricaded individuals. According to Kastell, this instant represented the first time anywhere a police force equipped itself with a toxic agent for law enforcement purposes. A team from the Quai des Orfèvres (1st Arrondissement of Paris) deployed the agent for the first time in March 1913 to remove a disturbed young person.

Later the French police also received a sprayer (end 1913 or early 1914), a hand grenade and a grenade to be fired from a handheld gun. The hand grenade the police refused to use because of the dangers posed by its splintering. Made of brass, it weighed 450 grammes, including 250 grammes of agent. The handheld gun could project a shell with a canister over a distance of 100 metres. Within that range the shell had the capacity to penetrate doors, windows and brick partitions. The police never used it operationally because of the complexity of its operation under siege conditions.

Lépine was not considering the agent for dispersing crowds. In fact, first use of a tearing agent for breaking up protesters in France did not take place until November 1938. Even though a much greater volume of lachrymator was dispersed over a wide area, its purpose was still to drive out strikers barricaded inside the Renault factory at Boulogne-Billancourt (west of Paris). His principal concern was avoiding unnecessary bloodshed. His motivation and logic were therefore like that of military thinkers in the 19th century looking for means to evict enemy soldiers from heavily fortified positions.

When Kling and Florentin were arguing the absence of asphyxiating or deleterious characteristics of ethyl bromoacetate, they adopted terminology from the Hague Declaration (IV, 2). ‘Smothering’ or ‘narcotic’ functioned as euphemisms for ‘toxic’, a word semantically too close to the terms in the international agreement. ‘Lachrymatory gas’ did not gain currency until 1915, more than half a year into World War 1. Such sensitivity is surprising considering that the document was part of the international laws of war. While correct that the French police were developing and eventually deploying projectiles that had no other purpose than disseminating a toxic agent, these were not meant for use on a battlefield against another party to the agreement.

Unless the French military had already been investigating such weapons with different intent.

Breaching through a fort’s loophole

It took the Parisian police a mere five months from the constitution of the special civil-military commission to the testing and adoption of the pistol that fired a cartridge filled with the substance whose vapours are extremely irritating to the eyes. It is therefore likely that Lépine’s special commission benefited from an earlier secret commission set up in November 1905 under the Directory of the Artillery to investigate the military utility of chemical irritants.

Following the 1904–1905 Russo-Japanese war, French military engineers had begun studying how to seize military fortifications and were looking into toxic chemicals suitable to neutralise the defenders. The secret commission’s mandate included the investigation of ‘gas not covered by the Hague Convention, that is to say neither asphyxiating nor deleterious, of simply malodourant gas but which must smell so bad that any position should become untenable’ (gaz ne tombant pas sous le coup de la convention de La Haye, c’est à dire ni asphyxiants, ni délétères, de gaz simplement puants mais qui devaient sentir tellement mauvais que toute position devrait devenir intenable). Whoever wrote the instruction clearly knew of the potential to violate the Hague Declaration (IV, 2) Concerning Asphyxiating Gases if such weapons were ever used in war.

The construction of the mandate is important. The ban in the international agreement focusses clearly on the means of delivery rather than on the payload. It also concentrates on the purpose of the projectile: ‘the object of which is the diffusion of asphyxiating or deleterious gases’, the concern of several diplomats and military experts being that explosive shells may accidentally produce toxic fumes as a side effect of a detonation. Such possibility was exactly what Lépine sought to exploit when justifying the use of dynamite in Nogent-sur-Marne.

Two possible ways to circumvent the Hague Declaration lay open. First, one could deliver asphyxiating or deleterious gases via other means than a projectile. This was the German choice when it released chlorine from cylinders near Ypres in April 1915. Second, one could fill the projectile with a noxious chemical that was neither asphyxiating nor deleterious. That is, not lethal or harmful. In other words, a toxic chemical whose effects on humans would be transient. Hence the reference in the instructions to the secret military commission to malodourants. Nobody could withstand the rotten egg smell of hydrogen sulphide gas in an enclosed space, for instance. H₂S was one compound military thinkers in the 19th century had been considering.

Having tested some 30 substances, some of which proved quite aggressive, the military commission rejected most. It settled on ethyl bromoacetate, a liquid organic compound whose method of synthesis the British chemists William H. Perkin and Baldwin F. Duppa had published in 1858. It posed the lowest risk for violating the international agreement. In 1909 a Commission of Military Engineers began experimenting with delivery means. They included a hand grenade, a gun grenade and a grenade projector, three types of weaponry later proposed to but not adopted by the Parisian police force.

None of the sources consulted for this blog posting claims that the French army adopted the weaponry before the outbreak of the war. When French soldiers fighting in the Alsace late in August 1914 first fired lachrymatory shell from portable guns at the Germans, Kastell suggests that the weapons may have been borrowed from the police. According to the classic volume on the history of chemical and biological warfare (p. 129) by the Stockholm International Peace Research Institute, a conscripted French police officer returned from leave with some grenades. If correct, this person may have been a member of the Parisian police’s special gas brigade trained in using the novel smothering weapons. Just like the German High Command never believed that it was violating international law when authorising the release of chlorine from cylinders in 1915, French soldiers may have been equally convinced that they were committing no war crime when discharging their handheld guns.

The French military commission’s mandate is therefore likely the first document that separated non-lethal chemical agents from lethal or otherwise injurious ones to justify the legality of the use of certain toxic weapons in a context of general prohibition.

A convoluted weapon development process

The dynamic to weaponise irritant chemicals swung from military considerations to civilian purposes and back several times. Initially, the idea put forward by some military thinkers during the 19th century was to force defenders from heavily fortified positions that then existing artillery could not breach. The suggestion never got much traction among political decision makers.

Following the Russo-Japanese war the military, at least in France, revisited the question of defeating heavily reinforced positions and specifically investigated the options of toxic chemical agents. However, since France had signed up to the 1899 Hague Declaration (IV, 2), the compound could neither be lethal nor injurious. This constraint led to the proposal for ethyl bromoacetate, a powerful lachrymatory agent if used against unprotected people in confined spaces. Other candidate agents the secret military commission rejected because they were too aggressive, implying that the multilateral agreement still functioned as a filter. Even though military engineers designed and developed a hand grenade and a projectile containing a canister to be fired from a handheld gun, France does not seem to have equipped military units with the chemical weapons before the German invasion in August 1914.

Meanwhile, French police in the Paris region had to confront a new form of extremely violent banditry in which criminals refused to surrender. Barricading themselves in buildings and armed with the latest weaponry, police officers supported by the military faced them off in bloody beleaguering. The development led to the consideration and eventual adoption of so-called non-lethal toxic chemical agents for law enforcement purposes.

Within weeks after the outbreak of World War 1 the military used the police weapons against the German invaders, convinced that the toxic agent was neither asphyxiating nor deleterious. This was one of two possible loopholes in the Hague Declaration (IV, 2) that made modern chemical warfare possible.

Obviously, not a single delegate at the First Hague Peace Conference had lachrymatory agents in mind. The term ‘lachrymatory agent’ did not gain currency until well after the German offensives into Belgium and France. Notwithstanding, a mere five years after the Hague Peace Conference, France was investigating the military use of chemical agents to be delivered by projectiles. However, by researching toxic agents that neither killed nor caused permanent harm, it carved out a loophole for irritants whose effects would cease as soon as a person vacated the structure in which he had barricaded himself.

With the end of World War 1 the calls to restrict chemical warfare grew louder. The 1925 Geneva Protocol prohibits the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices. The expanded phrasing clearly encompassed non-lethal technologies such as RCAs too, but did not prevent their use for civilian law enforcement. This opened the door for vested interests in the continuation of national chemical warfare programmes.

Chemical warfare institutions—most notably the US Chemical Warfare Service—actively promoted the research and production of irritants in pursuit of those goals. The core tools in this strategy were the creation and nurturing of social networks, the organisation of technology transfers between the military and commercial industry and the development of communication strategies (e.g. the non-lethal argument) towards policy makers and the public. Veterans from those special units remained in contact with each other through fraternities and their employment in the chemical industry after demobilisation facilitated this military-industry exchange. One poignant sales pitch the military offered industrialists was the ‘humane’ breakup of industrial strikes. Tear-gas offered an alternative to the police shooting strikers, so the argument went. With that, the pre-World War 1 argument of forcing criminals from barricaded positions shifted to one of riot control. In the United States, the new argument contributed to defeating the ratification of the Geneva Protocol and until today the country distinguishes sharply between lethal and other types of chemical warfare agents. It still denies that lachrymatory agent and herbicides used in the Vietnam War (1955-1975) amounted to chemical warfare.

As I wrote in my review of Anna Feigenbaum’s book ‘Tear-Gas’: ‘The rise of institutional and economic interests in the manufacture of tear-gas is tightly interwoven with the development of the non-lethal narrative as a powerful sales argument.’ The campaigns first mounted during the 1920 still reverberate today.