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Before the 1925 Geneva Protocol: First (mis)steps to constraining chemical weapons

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17 June is the anniversary of the signing in 1925 of the Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or other Gases, and of Bacteriological Methods of Warfare, more commonly known as the Geneva Protocol after the place where it was negotiated.

In a blog posting six years ago, I discussed how the negotiators of the Geneva Protocol stumbled across the dual-use dilemma when trying to control toxic chemicals so that belligerents would not be able to use them again as weapons of war. However, in the absence of a formal international treaty outlawing the use of chemical weapons (CW) they could not overcome the legal impossibility to regulate the production, consumption or trade of such compounds, let alone differentiate between legitimate and prohibited uses. The Geneva Protocol created that legal foundation, but it would take several years of technical committee meetings in the League of Nations before experts developed a set of principles that would become known as the General Purpose Criterion. First framed in its totality in the draft disarmament treaty before the Conference for the Reduction and Limitation of Armaments (February 1932 – November 1934), the concept of the General Purpose Criterion is still at the heart of the prohibitions in the 1972 Biological and Toxin Weapons Convention and the 1993 Chemical weapons Convention.

However, between the Armistice on 11 November 1918 and the signing of the Geneva Protocol the international community struggled with the legacy of chemical warfare in the First World War. The 1899 Hague Declaration (IV, 2) on Asphyxiating Gases had not held up and from the first chlorine attack in April 1915 until the last day of the war, the release of toxic chemical against enemy lines had become a daily occurrence. The 1919 Versailles Treaty imposed a coercive disarmament regime on Germany. It included an absolute prohibition on the acquisition and possession of CW. Germany’s allies had to accept similar provisions in their separate peace treaties.

The Washington Naval Conference agreed in 1922 on a paragraph to prohibit CW use. However, delegates had almost resigned to the inevitability of chemical warfare and proposed limits on CW use in line with the humanitarian principles against indiscriminate warfare.

How this was avoided and, despite the failure of the negotiated treaty, eventually led to the Geneva Protocol three years later is the story of this blog contribution.

Emerging battlelines over chemical weapons

It is not easy to capture the mood concerning CW in the first years after the war. By 1918 chemical warfare had become so ubiquitous that soldiers in the frontline lived permanently in a gas environment and were always – however slightly – exposed to the gases’ harmful effects. To them, and the people living behind the frontlines, gas had become one nuisance among so many, including rain, rats, disease, sniping and shelling.[1] CW had become conventionalised. The highest decision-making levels had delegated the authority to employ chemical shells to battlefield commanders. Protests against gas were limited to individuals or a gathering of eminent scientists, and emerging peace movements tended to protest the war as whole rather than as individual forms of warfare.[2] By the time the International Committee of the Red Cross (ICRC) issued its appeal against the use of poisonous gases on 8 February,[3] advanced protection and gas discipline preserved soldiers from the worst consequences of exposure, a point that post-war apologists of chemical warfare would never fail to make. Other weaponry and modes of warfare caused far higher casualty rates and exposed soldiers to intolerable levels of daily destruction, mutilation, and human suffering. In addition, on a strategic level commanders faced escalatory pressures from enemy technological development and innovative gas tactics. They needed to avoid physical and psychological degradation of fighting capacity that might be the consequence of one-sided enemy CW use. Under those circumstances, the humanitarian appeal backfired on the ICRC as both Allies and Germans questioned the organisation’s motives and bias.[4] Legal writers and diplomats expressed around the same time their despondency about the inability of international humanitarian law to curb the war’s excesses.

During the early 1920s the political battlelines over CW gradually became more entrenched as institutional interests in the continuation of chemical armament grew stronger, on the one hand, and sharp differences between idealists and pragmatists over how to counter future chemical threats coloured the opposition debates, on the other hand.

Apologists within the military-scientific community deflected any argument that no battle had been decisively influenced by gas. They argued that early means of dissemination had been crude and highly dependent on wind factors. In later stages of the war, so they claimed, artillery was still highly inaccurate. Moreover, more potent toxicants, such as lewisite, an organoarsenic vesicant, did not reach the frontlines in time to prove their worth. Time and time again they saw their view on the effectiveness in war proven right in the colonial campaigns. (They, however, usually failed to mention that the attacked could not retaliate and hardly possessed any protective equipment and shelters.) They built the core of their arguments on a line followed by Captain Alfred Thayer Mahan, US naval delegate at the 1899 Hague Peace Conference, when he argued that future weaponry may still prove decisive and not cause superfluous suffering in wars to come.[5]

The advocates of chemical warfare also maintained that toxicants are humane compared to classical weapons. Essentially, they countered emotional repugnance with the mathematical rationale of statistics. For example, the British officially listed 180,983 of their soldiers as gassed, of whom no more than 6,062 or 3.3% were killed.[6] The popular press maintained similar arguments for many years after the war. One American piece published in 1935 posited that 24 percent of US soldiers injured by shrapnel or bullets subsequently died, while only two percent of gas casualties proved fatal.[7] Such figures enabled them to present gas as a humane weapon that wounds rather than kills. That many casualties appeared to recover completely after a more or less prolonged span of time, reinforced their argument. At that time there were of course no statistics on long-term effects. The humane characteristic weighed heavily in the discussions between the two wars. Only later declassified documents revealed that whole categories of victims never made it into official statistics.[8]

In contrast to these macro-level arguments, opponents drew attention to the individual suffering of victims, which went beyond the acceptable to put a soldier hors combat, and the indiscriminate nature of gas clouds, which had caused innumerable civilian casualties. Already during the early 1920s strategic thinkers on air power, such as Italian General Giulio Douhet and US General William ‘Billy’ Mitchell, were advocating the integration of CW in aerial warfare.[9] Their writings led some to envisage apocalyptic chemical bombing raids against cities, leading to human losses beyond anything experienced thus far. Having listened to a presentation by a chemical expert a few days earlier, Ellen Wilkinson, MP, predicted in a speech to the House of Commons on 11 July 1927 that ‘the next war will be so destructive as to threaten the very existence of European civilisation’, adding that ‘our cities will be not merely decimated but rendered utterly uninhabitable by chemical bombs’.[10] A split in the opposition to chemical warfare emerged when some people and organisations advocated peacetime preparations to protect populations from chemical warfare and assist gas victims. In the eyes of those seeking a total ban on chemical warfare, such humanitarian pragmatism allowed for the possibility of chemical warfare. They viewed this as totally unacceptable.[11]

Restraining the impact of technological innovation on the battlefields

Caught between these macro and micro levels of the humanitarian argument were many politicians and diplomats. While they still desired to strengthen the humanitarian laws of war, they had lost faith in their value once the war demons were unleashed. Those rules might give the victor a ground of action, but they could not mitigate the horrors of war.[12] They came to realise that armaments rather than bolstering national security were actually a source of instability in international relations. If war were to be abolished as means to resolve disputes among nations, states would have to accept limits on national armaments. The General Treaty for Renunciation of War as an Instrument of National Policy (1928), more commonly known as the Kellogg–Briand Pact, concretised the first ambition.[13] The principle was to become a cornerstone of the Charter of the United Nations in 1945. Reining in technology-driven armament dynamics had been the original, but futile goal of the 1899 Hague Peace Conference.

Washington Naval Conference. (Harris & Ewing, photographer. Source:

US President Warren G. Harding called for ambitious reductions in naval and land armaments when he invited nine powers to the Washington Conference (12 November 1921 to 6 February 1922). His opening address captured the dual ambition of war prevention and arms control:

I can speak officially only for our United States. Our hundred millions frankly want less of armament and none of war. Wholly free from guile, sure in our own minds that we harbor no unworthy designs, we accredit the world with the same good intent.[14]

Besides arms limitation, the conference also covered two other areas: territorial and political settlements in the Asia–Pacific region and the development of rules for control of new agencies of warfare. The conference took place outside the auspices of the League of Nations because the United States had not yet decided on whether to join the international organisation. France, Great Britain, Italy, Japan and the United States comprised the powers discussing limits on armament. Belgium, China, the Netherlands and Portugal joined the five for the other issue areas.

While one might have expected that a mere three years after the Armistice humanitarian considerations and opposition to war would dominate the Washington Conference, balance-of-power politics drove the discussions. Great Britain ostensibly played to preserve its favourable quantitative ratio in surface ships relative to other naval powers, but in the end accepted parity with any other single country. The outcome was actually less of a concession. In March 1920, following the scuttling of the German fleet in Scapa Flow in June 1919 and in view of the restriction placed on German naval rearmament by the Versailles Treaty, the British Admiralty had already announced the sufficiency of parity. France refused second-tier status and insisted on an authorised tonnage for submarines equal to that tabled for Great Britain and the United States, a proposition wholly unacceptable to its cross-Channel rival. In addition, France refused to consider reductions in land armaments as long as, in the words of Prime Minister Aristide Briand on 21 November, Germany was not morally as well as materially disarmed.[15] French fear of revanchism effectively removed the matter from further deliberation. The United States seemed the only Allied victorious power willing to consider serious armaments limitations, even though attendants could observe that Washington and Tokyo were already viewing each other as geopolitical competitors in the Asia–Pacific region.[16] In this context, it fared poorly according to some observers because it accepted limitations on the size of its fleet and agreed to the non-fortification of the Pacific Islands.[17]

Controlling new agencies of warfare

Relative to the original ambitions the net outcome of these negotiations may have appeared meagre to contemporaries, but the Washington Conference nevertheless set a precedent for multilaterally agreed limitation and reduction of national armaments. The meeting also made some headway in the forum on Rules for Control of New Agencies of Warfare. It appointed three subcommittees to consider CW, aircraft and the rules of international law. The three topics in themselves reflected the confusion and doubts among political leaders and diplomats about the value of international laws of war in armed conflict but pressed by public opinion (as invoked by President Harding in his opening address) they had no choice but to improve and expand the rules.

The Subcommittee on aircraft concluded that it was impossible to prohibit the use of aeroplanes in war or effectively limit the number of planes or pilots. Governments had already built great stakes in the militarisation of the skies before the war. Curbs on the further development and expansion of air power they would therefore tend to resist. A resolution declared that ‘the use of aircraft in war should be covered by the rules of warfare as adapted to aircraft by a further conference which should be held at a later date’.[18] With the exception of a limitation on the tonnage of aircraft carriers in the Naval Treaty, the conference failed to impose any constraint on the competitive development of air forces.

Shifting from arms limitation to humanitarian law was the way the Washington Conference proceeded regarding submarines. In view of the French objections to the proposed aggregate tonnage for its submarine fleet, the only restriction in the Naval Treaty pertained to the size of the vessels. Besides balance-of-power considerations in seeking restrictions, there was the obvious experience from the First World War that submarines had principally attacked merchant vessels and thereby caused harm to neutrals and non-combatants. Great Britain, depending on sea lanes for its supplies, thus managed to safeguard in principle its merchant fleet through war regulations instead of arms limitation. However, even this outcome remained unsatisfactory in view of the lack of confidence in effective enforcement.[19]

Contemporary confusedness about the value of international regulation was on greatest display on the issue of poison weapons.

Humanitarian law confronted with technological innovation

Article 171 of the Versailles Treaty banned the use of modern CW without any qualifications. While this treaty did not apply universally, the five states participating in the arms limitation talks—France, Great Britain, Italy, Japan and the United States—were either party to the Versailles Treaty or to other bilateral peace agreements containing the same provision with the former Central Powers. It seems implausible that the US president intended to have the ban reconsidered. More likely, he wanted to reinforce the norm against gas in view of the experiences in France and Belgium.

The Subcommittee on chemical warfare, however, developed logic similar to that in the Subcommittee on aircraft, concluding in its report of 6 January 1922:

(c) Research which may discover additional warfare gases cannot be prohibited, restricted or supervised.
(d) Due to the increasingly large peacetime use of several warfare gases. It is impossible to restrict the manufacture of any particular gas or gases. Some of the delegates thought that proper laws might limit the quantities of certain gases to be manufactured. The majority of opinion was against the practicability of even such prohibition.
(f) The kinds of gases and their effects on human beings cannot be taken as a basis for limitation. In other words, the committee felt that the only limitation practicable is to wholly prohibit the use of gases against cities and other large bodies of noncombatants in the same manner as high explosives may be limited, but that there could be no limitation on their use against the armed forces of the enemy, ashore or afloat.[20]

The US experts in the subcommittee, in the words of US-educated Japanese writer Sotokichi Katsuizumi, ‘were firmly for the unrestricted use of poison gases’.[21]

The US delegation drew on national public opinion as a deft manoeuvre to check its own experts without open confrontation and overcome the potential legitimisation of chemical warfare. The General Board of the United States Navy recommended unreservedly that gas warfare be prohibited, because it ‘threatens to become so efficient as to endanger the very existence of civilization’. The Advisory Committee of the American Delegation also argued that ‘chemical warfare, including the use of gases, whether toxic or non-toxic, should be prohibited by international agreement, and should be classed with such unfair methods of warfare as poisoning wells, introducing germs of disease, and other methods that are abhorrent in modern warfare’.[22]

On the same day of the subcommittee’s report, Elihu Root, former Secretary of State and member of the US delegation, tabled a resolution citing the language in the Versailles Treaty to counter the report’s conclusion.[23] With a few minor editorial modifications it became Article V of the Treaty Between the United States of America, the British Empire, France, Italy, and Japan, to Protect Neutrals and Non-combatants At Sea in Time of War and to Prevent the Use in War of Noxious Gases and Chemicals:

The use in war of asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices, having been justly condemned by the general opinion of the civilized world and a prohibition of such use having been declared in Treaties to which a majority of the civilized Powers are parties,
The Signatory Powers, to the end that this prohibition shall be universally accepted as a part of international law binding alike the conscience and practice of nations, declare their assent to such a prohibition, agree to be bound thereby as between themselves and invite all other civilized nations to adhere thereto.[24]

The outcome merely reaffirmed an already established rule, but it denied chemical warfare future legitimacy on the battlefield. Article V also defeated the idea that international law could not restrain the use of gas. At the Sixth Plenary Session on 4 February 1922 the Washington Conference agreed to constitute a Commission to consider the rules of international law respecting new agencies of warfare, but in a separate resolution determined ‘to exclude the said Commission from reviewing the rules already adopted by the Conference relating to submarines or the use of noxious gases and chemicals’.[25] The latter decision foreclosed a possible replay of the logic driving discussions in the Subcommittee on chemical warfare.

Besides the diplomatic jockeying in the pursuit of national interests, two other elements seem to have contributed to the negotiation dynamic: pessimism about the ability of international law to restrict novel war fighting technologies and abandonment of regulating specific weapons or modes of combat in favour of more general principles of warfare. The diplomats concluded with respect submarines, aeroplanes and CW that the laws of war could not govern specific weapon types used to devastating effect in the First World War. They felt that the technologies had not yet fully matured. They could not control national programmes to further investigate their full potential and, therefore, halt the arms competition between nations. If anything, the 1899 Hague Declaration (IV, 2) on asphyxiating gases had proved to them how easily battlefield imperatives could circumvent a specific rule. France’s forceful rejection of any limitation of land armaments – Prime Minister Briand had especially sailed to the United States to make that point – and refusal to accept quantitative limits on submarines attested to the primacy of peacetime national interests over international laws of war. It underscored the impossibility of restricting national armaments (which after all had been a key goal of the Washington Conference).

Multilateral arms control, an idea ahead of its time

Meeting records and post-conference considerations actually reflected the disarray about how to address the challenges posed by modern CW and peacetime preparations for chemical warfare, all the while realising contemporary humanitarian law’s futility in constraining the use of gas on the European battlefields. In a review of the achievements, Canadian delegate Sir Robert Borden captured the resigned scepticism about Article V’s utility or added value:

The question is not free from difficulty. Every investigation into the subject has shown the practical impossibility of preventing in time of peace preparations that would enable noxious gases to be produced on a great scale in time of war; so that it is impossible for nations that have no intention of employing this weapon, to abandon inquiry into the means by which its attacks may be resisted and if necessary countered. Doubtless the rule will not have the effect of preventing such preparation. On the other hand, those who are anxious to make war more humane should not be deterred by these considerations from condemning the misuse of scientific discovery for such purposes. In any case the rule does no more than to reaffirm existing international law.[26]

With multilateral arms control an idea whose time had not yet arrived, diplomats were left with sole recourse to the general principles and rules of armed combat. Protection of neutrals and non-combatants are age-old cornerstones of international humanitarian law. Safeguarding these categories of people from the worst consequence of new technologies was the best they felt they could achieve. For aeroplanes, they determined that a future conference had to adapt the principles of land warfare to the skies. The flow of logic also explains the oddity why restrictions on submarine warfare and noxious gases ended up in a single, self-contained document. Both rules were the Washington Conference’s only contributions to the development of the laws of war. In the case of CW, the new elements—small as they may have appeared to contemporaries—were the framing of the prohibition outside of the context of the peace conditions on Germany and Article V’s call for universal adherence.

Another effort during the early 1920s was the Convention for the Limitation of Armament agreed at the Conference on Central American Affairs. Five countries signed it on 7 February 1923 and the accord entered into force on 24 November 1924. Its Article V adopted the essence of the prohibition on chemical warfare in the Washington Treaty:

The contracting parties consider that the use in warfare of asphyxiating gases, poisons, or similar substances as well as analogous liquids, materials or devices, is contrary to humanitarian principles and to international law, and obligate themselves by the present convention not to use said substances in time of war.[27]

In addition, the Pan-American Conference, which held its fifth summit meeting in Santiago, Chile from 25 March until 3 May 1923, recommended in a resolution that its members become a party to the Washington Treaty.


Despite their efforts to control novel weapon technologies, the diplomats and experts made little headway because they had limited understanding of what exactly they ultimately wanted to control – battlefield use, weapon stockpiles, production capacity or volumes, etc. Absent clear purpose, deciding which proposed definition serves the armament limitation goal best was impossible.

Unbeknown to them, with CW they were closing in on the security dilemmas posed by ‘dual-use technologies’. These comprise knowledge, skills, equipment, processes, and artefacts that may have both civilian and military application. Dual-use questions arise when the attempts to control a particular type of weapon-relevant technology confront the non-military commercial and scientific interests in such technology. Rather than treating arms, science and industry as separate spheres, arms control and disarmament require their integrated consideration.

Diplomats and technical experts at the Conference for the Supervision of the International Trade in Arms and Ammunition and in Implements of War, which opened in Geneva on 4 May 1925 and lasted until 17 June, came rather unexpectedly face to face with the dual-use dilemma after they had accepted the US proposal to ban the trade in CW. The reason was straightforward: the question of CW control got reframed as one of arms trade regulation. Instead of having to focus on the consequences of CW use on the battlefield, they had to grapple with the technical properties of toxic compounds to distinguish their legitimate applications from potential battlefield use. [See 2015 blog post]

Lacking the time and the resources to resolve the dual-use dilemma, they agreed on the Geneva Protocol. While the 1922 Treaty never entered into force because of France’s refusal to ratify it over objections to the constraints on submarine warfare, the language in Article V nevertheless inspired the delegates in Geneva when framing the Protocol text.

(Excerpted and adapted from ‘The road to Geneva’, Innocence Slaughtered, 2015)



[1].Cf. T. Cook, No Place to Run. The Canadian Corps and Gas Warfare in the First World War (UBC Press: Vancouver, 1999), p. 177.

[2].L. van Bergen and M. Abbenhuis, ‘Man-monkey, monkey-man: neutrality and the discussions about the “inhumanity” of poison gas in the Netherlands and International Committee of the Red Cross’, Innocence Slaughtered; P. Van den Dungen, ‘Civil Resistance to Chemical Warfare in the 1st World War’, Innocence Slaughtered.

[3].International Committee of the Red Cross, Appeal against the use of poisonous gases, 8 February 1918, available from <>.

[4].Van Bergen and Abbenhuis, ‘Man-monkey, monkey-man’.

[5].Captain A. T. Mahan, Report to the United States Commission to the International Conference at the Hague, on Disarmament, etc., with Reference to Navies, in J. Brown Scott, The Hague Peace Conferences of 1899 and 1907. A Series of Lectures Delivered before the Johns Hopkins University in the Year 1908, Volume II (The Johns Hopkins Press: Baltimore, MD, 1909), p. 37.

[6].R. Harris and J. Paxman, A Higher Form of Killing (Triad/Granada, UK, 1982), p. 34.

[7].W. Gilman, ‘Devastating poison gas—the Army planes’ ally’, Popular Aviation, vol. 17, no. 3 (September 1935), p. 145.

[8].Harris and Paxman, A Higher Form of Killing, p. 34.

[9].G. Douhet, The Command of the Air (1921), Translated from Italian by Dino Ferrari (Coward-McCann: New York, 1942), reprinted in Project Warrior Studies, Office of Air Force History, Washington, DC, 1983, p. 58. William Mitchell, Statement before the House Appropriations and Naval Affairs Committees, 28 January 1921, as cited in T. Wildenberg, Billy Mitchell’s War with the Navy: The Army Air Corps and the Challenge to Seapower (Naval Institute Press: Annapolis, MD, 2014). Further examples of claims about the destructiveness of chemical bombs in T. H. Greer, The Development of Air Doctrine in the Army Air Arm 1917-1941 (USAF Historical Division, Research Studies Institute, Air University: Maxwell Air Force Base, AL, 1955), reprinted by Office of Air Force History, Washington, DC, 1985.

[10].Ms Ellen Wilkinson (MP), Hansard, Series 5, Vol. 208, Commons, Sittings of 11 July 1927, pp. 1859–61, available at <>.

[11].Van Bergen and Abbenhuis, ‘Man-monkey, monkey-man’.

[12].Q. Wright, ‘The Washington Conference’, American Political Science Review, vol. 16, no. 2 (1922), p. 292.

[13].League of Nations, Treaty Series, vol. 94 (1929), pp. 57–64.

[14].W. G. Harding, Opening Speech of the Conference on Limitation of Armament, 12 November 1921, Miller Center, University of Virginia, URL <>.

[15].Address by Mr Briand, Third Plenary Session, 21 November 1921, as reproduced in Conference on the Limitation of Armament, Held At Washington, November 12, 1921, to February 6, 1922. Report of the Canadian Delegate, Including Treaties and Resolutions (F. A. Acland Printer to the King’s Most Excellent Majesty: Ottawa, 1922), pp. 92–99, especially at pp. 95 and 98.

[16].Wright, ‘The Washington Conference’, pp. 287–89.

[17].R. L. Buell, ‘Review: M. Sullivan, The Great Adventure at Washington: The Story of the Conference’, Political Science Quarterly, vol. 37, no. 4 (December 1922), pp. 695–96.

[18].R. L. Buell, The Washington Conference (D. Appleton and Company: New York, 1922), p. 210.

[19].Ibidem, p. 228.

[20].‘Text of the Conference discussions’, New York Times, 7 January 1922, p. 3.

[21].S. Katsuizumi, Critical Observation on the Washington Conference (Ann Arbor, MI, 1922), p. 25.

[22].Reports as reproduced in ‘Text of the Conference discussions’.

[23].Buell, The Washington Conference, pp. 208–09; also Katsuizumi, Critical Observation on the Washington Conference, pp. 25 and 28. Katsuizumi attributed the diplomatic manoeuvre to the US having been outvoted by other subcommittee members and unwilling to recognise the more principled stance of other nations, Japan foremost.

[24].D. Schindler and J. Toman, The Laws of Armed Conflicts (Martinus Nijhoff Publishers: Dordrecht, 1988), pp. 877–79.

[25].Resolutions reproduced in Conference on the Limitation of Armament, Report of the Canadian Delegate, p. 214.

[26].Conference on the Limitation of Armament, Report of the Canadian Delegate, p. 25.

[27].A. Boserup, The Problem of Chemical and Biological Warfare, Volume III: CBW and the Law of War (SIPRI and Almqvist & Wiksell: Stockholm, 1973), p. 154.

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