A revolution in weaponry

The nineteenth century saw a revolution in infantry weaponry that started with the use of muskets and gunpowder and culminated in the 1890s with rifling and metal cartridges.Footnote ¹² Expanding bullets arose at the tail end of this century following a series of developments in conventional weapons, rifling and ammunition that led to enormous increases in the destructive power of infantry weapons and changes to the balance of power in the non-Western and Western worlds.Footnote ¹³ These developments increased the rate of fire of weapons, their striking range and their wounding capacity,Footnote ¹⁴ and together with the increase in military expenditures internationally, led statesmen and observers at the end of the century to view rising armament levels as a challenge that required the active intervention of States. International law could provide the solution to this challenge by better organizing international society.Footnote ¹⁵

The origin of expanding bullets – also known as hollow-point or dum-dum bullets – is tied to this revolution in infantry weaponry. Expanding bullets contain a notch at the tip, uncovered by the metal casing, that causes them to expand upon hitting a target.Footnote ¹⁶ They are “specialised bullets designed to deform upon impact because of a collapsible space within the projectile tip”.Footnote ¹⁷ Though used for hunting as early as the 1870s, their development passed through several variations, which included the Mark III, Mark IV and Mark V .303-inch rifle bullets manufactured at the Woolwich Ordnance Factory and in associated factories across the British Empire.Footnote ¹⁸ Expanding bullets were regarded as indispensable in colonial fighting against non-Western forces and were used, inter alia, in India’s northwestern frontier and in Sudan in 1898.Footnote ¹⁹ Their use carried several benefits, including a decreased risk of ricochet due to the reduced overall penetration distance and a greater ability to stop enemy combatants quickly.Footnote ²⁰

The reasons that linked expanding bullets to other inhumane or prohibited weapons have been extensively explored. Expanding bullets went “beyond what was necessary to stop enemy combatants”,Footnote ²¹ and were perceived to be inhumane due to the unnecessary suffering and superfluous injuries they caused.Footnote ²² Unlike the projectiles fired by guns until the middle of the nineteenth century, expanding bullets represented a major increase in wounding capacity.Footnote ²³ They inflicted considerably more severe injuries in comparison to conventional, full metal jacket bullets, had a higher stopping power and aimed to kill rather than merely incapacitate.Footnote ²⁴

The increased severity of the injuries caused by expanding bullets is linked to their design. Full metal jacket bullets remain stable in their “passage through tissue for a variable distance before turning side-on”, with this deeper penetration meaning that “they may pass through the victim’s body without causing as much tissue damage”.Footnote ²⁵ Expanding bullets, in contrast, are perceived to cause larger wounds due to how they expand within tissue and deposit kinetic energy earlier in the wound track than full metal jacket bullets.Footnote ²⁶ To their opponents, it was this greater capacity to inflict severe wounds that made the use of expanding bullets illegitimate. They went beyond merely disabling enemy combatants, which was sufficient in war, and increased the probability of death or long-term disablement.Footnote ²⁷

A considerable amount of late nineteenth- and early twentieth-century scientific, medical and legal literature analyses the wounding capacity and effects of expanding bullets. This literature reflects the horror that expanding bullets were regarded with. Ballistic scientists, legal scholars and military thinkers saw expanding bullets as “uniquely capable of imposing undue amounts of physical pain in addition to killing the target”.Footnote ²⁸ The commentaries written by medical professionals on the wounding capacity of different types of ammunition also stand out within this literature, particularly due to how they passed judgement on the nature of wartime wounds and the levels of violence that ought to be allowed within the laws of war.Footnote ²⁹

Cuthbert S. Wallace’s 1901 account of typical and atypical bullet wounds is a prominent example of this literature. Typical small-bore bullets, Wallace wrote, made a round hole slightly smaller than the bullet itself, whilst wounds made by expanding bullets were always associated with fractures of bone.Footnote ³⁰ Though the entry wound of an expanding bullet was typical and otherwise unremarkable, the introduction of a finger often showed “that a still larger irregular cavity is formed into which the ends of the fractured bone protrude”.Footnote ³¹ The damage that expanding bullets caused upon impact was also further noted and contrasted with that of full metal jacket bullets and explosive bullets. Expanding bullets were, as such, deadly, a fact that made them particularly suited for big-game hunting.Footnote ³²

W. F. Stevenson also made note of the wounding capacity of expanding bullets in a similar article. The wounds produced by them were severe: “pieces of the core and jagged strips of the envelope are scattered widely through the part struck, remaining lodged in the part to set up surgical complications later on”.Footnote ³³ This wounding power was not incidental – on the contrary,

An 1899 article in the Bulletin International des Societes de la Croix-Rouge further emphasized the deadly nature of expanding bullets. The article noted that they deform more easily than non-hollowed bullets, causing them to cause a higher amount of severe bone fractures at distances of up to 600 metres.Footnote ³⁵

The severe wounds caused by expanding bullets, therefore, made their use in armed – as opposed to colonial – conflicts appear inhumane and contrary to the basic principles of IHL. While full metal jacket bullets were relatively humane, expanding bullets “increased the chance of the bullet remaining in the body and [causing] an ‘explosive-type’ wound which made death more likely to happen”.Footnote ³⁶ They denied quarter to enemy combatants who were hors de combat and caused unnecessary suffering. Expanding bullets therefore ran against the only legitimate object of States in war – to weaken the military forces of the enemy – and the laws of humanity.Footnote ³⁷ This linked them to the 1868 St Petersburg Declaration, which highlighted how the only legitimate purpose of States in war is to weaken the military forces of the enemy and that the employment of weapons which “uselessly aggravate the sufferings of disabled men” was contrary to the laws of humanity.Footnote ³⁸ They were therefore, due to their higher wounding power, against the laws of humanity.

Having examined the development and treatment of expanding bullets in nineteenth-century medical literature, we will now turn to how these factors, together with military interests, influenced calls to ban expanding bullets in armed conflicts.

Military utility, outcry and indignation

Substantial national and military interests contributed to the decision to both negotiate and ratify the Hague Declaration. These interests were present at the start of the 1899 Hague Conference and coexisted with the horror associated with the use of expanding bullets. The 1899 Hague Conference was a highly politicized event; though Tsar Nicholas II’s circular calling for the Hague Conferences appealed directly to international morality and sought to halt the arms race, the call was also motivated by substantial national interests.Footnote ³⁹ These same national interests influenced the decision of other countries to support the ban on expanding bullets – but they were also present in Britain’s defence of such bullets, which was at the heart of its adoption of a new generation of rifle ammunition.Footnote ⁴⁰

Germany and Austria-Hungary had recently acquired quick-firing artillery. The cost of refitting the Russian army with this new type of gun would have played havoc with the national budget, and Russian minister of war Aleksei Kuropatkin “suggested a bilateral arrangement with Austria-Hungary to defray this expense, or at least to postpone it for a few years”.Footnote ⁴¹ The end-of-century arms race was burdening Russia’s economy, with military expenditures running at around 4.4% of the net national product, and Russian general staff foresaw great difficulties in renovating the Russian artillery stock.Footnote ⁴² Tsar Nicholas II’s call also followed the development of a new weapon – the expanding bullet – which meant that the “underdeveloped empire faced the introduction of another technologically advanced weapon into world arsenals”.Footnote ⁴³ The shift from a bilateral discussion with Austria-Hungary to a multilateral conference on the limitation of armaments reflected Russian concerns about the political fallout of a direct request to Austria-Hungary, which could disfavour negotiations that excluded its ally, Germany.Footnote ⁴⁴

The reasons that prompted European governments to seek the prohibition of expanding bullets stand out when contrasted with other, rapidly-evolving deadly technologies of the time.Footnote ⁴⁵ The new, small-bore weapons that had been introduced throughout Europe in the late nineteenth century were lighter than their predecessors, fired ammunition that travelled at much higher velocities, and inflicted wounds that could be as severe as those that were caused by expanding bullets.Footnote ⁴⁶ Artillery shells, meanwhile, had grown in size and explosive power, and “Maxim and Nordenfelt guns, mines, submarines, torpedoes, and Lyddite shells enhanced the wounding and killing capacities of all major armies”.Footnote ⁴⁷ Expanding bullets, however, were associated with the British Empire: they “‘stood in’ for British influence in the world”.Footnote ⁴⁸ The ire of States against expanding bullets was therefore linked, in part, to national interests.

The challenge to expanding bullets came not only from a Russia that was falling behind in the arms race; it also came from an aggressively militaristic Germany.Footnote ⁴⁹ Professor Paul von Bruns of Tübingen notably reported on the effect of British expanding bullets after firing them into the carcasses of animals. The publication of this experiment’s report resulted in an appeal to ban expanding bullets from eminent surgeon Professor Friedrich von Esmarch of Kiel to representatives at the 1899 Hague Conference.Footnote ⁵⁰ This appeal highlighted the double standard to which expanding weapons were held because of the advantages brought about by their use in colonial warfare:

The explicit defence of the use of expanding bullets against “uncivilized” peoples lays bare the political calculations underpinning this declaration. Such defences highlight how the grievous injuries inflicted by these bullets were permissible against “barbarous races, or against nations which are partly civilized, but who do not understand, and so fail to observe, the laws of war”, and which “yield only to superior force or superior cunning”.Footnote ⁵² Expanding bullets might have been inhumane when used against civilized nations, but their use against non-States Parties to the St Petersburg Declaration or “uncivilized” communities that fell outside of the laws of war was a different story.Footnote ⁵³

Britain’s defence of expanding bullets was heavily influenced by their considerable utility in colonial warfare. Their stopping power and higher velocity at short range meant that they could stop a charging enemy.Footnote ⁵⁴ The British Army felt that they were indispensable against non-European forces, “who refused to stop fighting upon being shot as a ‘civilised’ soldier would”.Footnote ⁵⁵ Crossman’s 1915 article highlights their specific use in colonial warfare:

Crossman was not the only writer to highlight this concern. An 1895 article in the Coventry Herald highlighted the dangers posed by other, non-expanding types of ammunition which theoretically could not stop a rush of determined enemies.Footnote ⁵⁷ The Bognor Regis Observer reiterated this claim in an 1899 article asserting that Boer combatants did not realize they had been hit by Lee-Metford bullets until long after the fact.Footnote ⁵⁸ For the British War Office, therefore, expanding bullets were an indispensable weapon. For other governments at the Hague, however, “a ban of the dum-dum offered an effective achievement on arms limitation without great cost”, as few armies other than Britain’s employed them in combat.Footnote ⁵⁹

Other contemporary literature reflects these ideas and concerns, and reveals the interests underpinning the ban on expanding bullets. J. B. Hamilton and Arthur E. Barker highlighted the irony involved in arguing for a peaceful way of waging war and questioned the varying inhumanity of expanding bullets when used against either “civilized” or “savage” men. War, they wrote,

Szabla articulates the questions that arise from Britain’s position regarding expanding bullets at the 1899 Hague Conference as follows: “Did Britain’s previous concern for international law in colonial combat inform its desire to exempt ‘savages’ from it? Or was Britain laying the groundwork for a lower universal standard, as some have suggested?”Footnote ⁶¹ For Britain, the use of expanding bullets was necessary in order to protect its own soldiers against enemies that could not be stopped with a standard full metal jacket bullet. This fact stood despite the grievous wounds that expanding bullets could inflict.

Having examined the conflicting ethical considerations and national interests that influenced the call to ban expanding bullets, we will turn to the way they impacted the 1899 Hague Conference. This will be done through an examination of how national interests, the idea of humanity and weapon lethality surfaced within the discussions on the prohibition of expanding bullets that took place at the Conference. A notable aspect of some of the arguments against the prohibition was that they did not deny the wounding power of expanding bullets but instead chose to highlight their tragic necessity.

The 1899 Hague Conference

It was the use of expanding bullets in colonial warfare that gave rise to efforts to outlaw them at the 1899 Hague Conference.Footnote ⁶² That the Conference directly aimed to mitigate the horrors of war is relevant in this respect, with Baron Georg Friedrich von Staal’s speech at the Conference’s Second Meeting clearly illustrating the depth of this aspect of the event:

Von Staal added that should it be impossible to eliminate armed conflict, “it would still be a labor [on] behalf of humanity to mitigate the horrors of war”.Footnote ⁶⁴

Though expanding bullets were originally not listed in Tsar Nicholas II’s programme for the Conference, their inclusion was raised by the Swiss and Dutch delegations.Footnote ⁶⁵ This action was motivated by the enormous public reaction that followed the British use of expanding bullets against Mahdist enemies in Sudan, which “inflicted the most horrendous wounds, the ‘terrible severity’ of which caused tens of thousands of casualties”.Footnote ⁶⁶ This public reaction, in turn, had a considerable influence on the Hague Declaration, which was the “product of a media spectacle that revolved around Britain’s deployment of dum-dum bullets”, making efforts to limit the use of such bullets an easy success story for diplomats.Footnote ⁶⁷

The prohibition on expanding bullets was first proposed at the Sixth Meeting of the 1899 Hague Conference, where delegates pushed for the ban despite the defences articulated by Great Britain and the United States – both colonial powers.Footnote ⁶⁸ Colonel Gilinsky, a Russian technical delegate, emphasized how the two wars in which the bullet had been used had “shown it to be such as to inflict wounds of great cruelty” and noted the similarities between the British bullet and that used in von Bruns’ experiments, which highlighted the grievous injuries it caused.Footnote ⁶⁹ General J. C. C. den Beer Poortugael, one of the Netherlands’ delegate plenipotentiaries, argued that guns of small calibres were sufficient to stop the attack of enemies;Footnote ⁷⁰ he also stated that his government had charged him to demand the “formal interdiction of the use of the dumdums and similar projectiles, which make incurable wounds” and “enormous ravages in the body”.Footnote ⁷¹ The Austrian delegate further supported the motion on account of the uselessly cruel wounds inflicted by these bullets.Footnote ⁷²

British delegate Sir John Ardagh’s depiction of expanding bullets as being like any other projectile and defence of their use against “savage races” caused general consternation.Footnote ⁷³ Upon hearing this argument, Arthur Raffalovich, the Russian councillor of State and technical delegate, argued that the ideas Ardagh had expressed were “contrary to the humanitarian spirit which rules this end of the nineteenth century”.Footnote ⁷⁴ Other delegates further noted the extensive injuries and excruciating internal wounds caused by expanding bullets, which rendered them needlessly cruel.Footnote ⁷⁵ All delegations save for Great Britain and the United States voted to proscribe expanding bullets.

The prohibition of expanding bullets raises questions in relation to the levels of lethality that are deemed to be acceptable. Britain’s defence of expanding bullets within the 1899 Hague Conference underscored the double standard involved in attributing their severity solely to the design of their mantle. All the bullets developed in Austria, Germany, France, Sweden, Portugal, Denmark, Japan and Peru were larger than those used by Britain, and at short ranges, the British bullet was the slowest. The mantle of the bullet was not the only factor in the damage it caused: velocity and weight were also crucial, and in fact were the primary destructive forces.Footnote ⁷⁶ In other words, “if dum-dum and hollow-point bullets were to be condemned, so too should all modern mantled bullets of small caliber, since they all produced terrible wounds”.Footnote ⁷⁷ This raises questions about the standard by which lethality was judged in relation to ammunition within this period and how, in banning expanding bullets, other novel military technologies and types of ammunition of this period were legitimized.Footnote ⁷⁸ It also gives rise to additional questions concerning the link between the prohibition of the use of expanding bullets and efforts to maintain imperial authority.Footnote ⁷⁹

Sir Alexander Ogston’s critique of the idea that the expanding bullet was anti-humanitarian, which focused on the grievous wounds caused by the ammunition used by other countries, highlights the specific logic of this argument. Attempts to portray fully mantled bullets as letting “the life out of a man by the smallest opening possible and in the gentlest way – an utopian sort of bullet” – were out of place.Footnote ⁸⁰ All modern bullets produced severe wounds and had horrifying consequences, and it was, therefore,

Dr Frédéric Ferrière, who had used the term “humanitarian bullet”, was similarly reluctant to adopt this terminology, and questioned whether said point of view had played a role in the development of bullets at all.Footnote ⁸² Clinton T. Dent also highlighted this in 1900: “Confusion arises from the fact that any form of high-velocity bullet may exert, under certain circumstances, an expanding or ‘explosive’ effect.”Footnote ⁸³ Ogston reiterated the same arguments in a separate publication later that year, in which he argued that the changes which bullets had undergone since 1868 allowed them to (1) lessen their diameter and propel the bullet with greater explosive force, increasing its velocity on impact; (2) increase their penetration power by encasing them in a hard mantle of nickel or nickel steel that prevented them from losing their shape when passing through the rifling of the barrel; and (3) kill or wound at much greater distances than earlier bullets.Footnote ⁸⁴ These three changes rendered all types of ammunition deadlier than those that had come before. In a 1914 publication, Stevenson further remarked on the irony of referring to Germany’s “new sharp-pointed bullet” as more humane than prior bullets such as the British Mark III, IV and V, on account of the German bullet’s tendency to “tumble” inside the body on meeting even the slightest resistance, with grievous consequences.Footnote ⁸⁵

British commentators questioned the methodology of Professor von Bruns’ experiment on expanding bullets, which had led to calls to ban them: von Bruns had employed “‘half-naked bullets’ … commonly employed by big game hunters in East Africa”, not a British model.Footnote ⁸⁶ Ogston criticized von Bruns’ experiment, arguing that it had not been carried out with dum-dum bullets at all, but with soft-nosed Mauser bullets manufactured in Germany. These projectiles were “too unlike the Dum-dum to justify us in at once accepting his conclusions as being true of it”.Footnote ⁸⁷ He reiterated this conclusion in an 1899 publication which highlighted how the “whole question of modern bullet wounds is far more complex and less perfectly known than the advocates of an international agreement excluding the bullets used by the English troops in India and the Soudan would have us believe”.Footnote ⁸⁸ Hamilton and Barker – whose article was examined in the previous section – focused on the expanding bullet’s humanity, stating that expanding bullets were more merciful due to how they were guaranteed to injure only one man rather than two or more when used in combat. Expanding bullets’ penetration power diminished rapidly, whereas other projectiles completely covered with nickel would “possibly pass through two or three men, and gradually ‘setting up,’ inflict great injuries on a fourth”.Footnote ⁸⁹ As such, this type of bullet was more humane precisely because of how it was deadly for a single person but, in turn, less deadly for those standing behind them.

These different ideas are reflected in Britain’s defence of the bullet at the 1899 Hague Conference. Sir John Ardagh argued at the Conference’s Third Meeting that the bullets used in von Bruns’ experiment and the British dum-dum bullet were different, and that the damage caused by the former could not “be accepted as evidence or proof against the dumdum bullet, which has an entirely different construction and effect”.Footnote ⁹⁰ Reiterating the importance of humanitarianism in Britain’s choice of weaponry, Ardagh asserted that “public opinion in England would never sanction the use of a projectile which would cause useless suffering”, and that “every class of projectile of this nature is condemned in advance”.Footnote ⁹¹ He also emphasized the tragic need to use expanding bullets, stating that fully jacketed bullets did not sufficiently protect British soldiers against determined enemies.Footnote ⁹² He reiterated the difference between the two bullets to Russian delegate General Gilinsky, after the latter emphasized the grievous wounds they caused: it was the von Bruns bullet, not the British dum-dum, that was needlessly cruel.Footnote ⁹³ It was these reasons, which appealed to the ethical and moral foundations of IHL, that forced Ardagh to vote “against a rule inspired by principles of which [he] wholly approve[d]”.Footnote ⁹⁴ The United States took a different position – Captain W. Crozier, a US delegate plenipotentiary, argued at the Conference’s Sixth Meeting that none of the evidence which had been presented so far at the Conference was enough to sit in judgement against the British dum-dum bullet.Footnote ⁹⁵ The dum-dum, he later said, “is condemned without proof, for there has been no effort made to show that it is needlessly cruel”.Footnote ⁹⁶

Great Britain did not adopt the Hague Declaration in 1899. However, though British newspapers defended Britain’s right to use expanding bullets and presented a case for their necessity, almost no newspaper came to the bullet’s defence during the Boer War, between 1899 and 1902.Footnote ⁹⁷ The Daily Mail lauded the British government for returning to the traditional Lee-Metford bullet in the Boer War following the 1899 Hague Conference.Footnote ⁹⁸ The Hague Declaration’s prohibition forced Britain to “carefully manage the propaganda around its use of expanding rifle ammunition after 1899 in imperial and non-imperial settings”.Footnote ⁹⁹ By the time Britain had adopted the Hague Declaration in August 1907, it had abandoned all plans to employ expanding bullets in combat.Footnote ¹⁰⁰ Britain’s military delegates recommended signing the Declaration only if it was a universally accepted ban, expressing fears about “facing an enemy armed with new bullets of ‘high stopping efficiency’ if Britain lacked the same ammunitions”.Footnote ¹⁰¹ These interests also played a role in the naval armament negotiations at the 1907 Hague Conference; the British Liberal government – which had only recently seen the end of the Boer War, the destruction of the Russian fleet in the Russo-Japanese war, and the launching of the HMS Dreadnought in 1906 – also hoped to reduce its military budget and save in operation and construction costs whilst other nations built their own dreadnoughts.Footnote ¹⁰² This highlights the dual currents of humanitarianism and strategic interests which underpinned both the negotiations at the Hague and the use or non-use of certain weapons.Footnote ¹⁰³

The power and influence of the 1899 Hague Conference stemmed from the momentum that Tsar Nicholas II’s call found in the public sphere. This public reaction forced world statesmen to consider the public profile and impact of any public mobilization “behind various causes in the wake of [Nicolas II’s call] and their own positions on key issues to be discussed at The Hague”, and opened a new era of public diplomacy.Footnote ¹⁰⁴ This shows the apparent strength of the norm associated with expanding bullets, which came to represent a resolute standard of barbarism in public diplomacy and an unconscionable weapon regardless of the circumstances of their use. No “civilized” State could employ this bullet without rebuke, even when used in colonial warfare, and its demonization following the Conference was near-universal.Footnote ¹⁰⁵

Having examined the different national interests associated with the use of expanding bullets and their influence on the proceedings of the 1899 Hague Conference, we will turn to the influence of expanding bullets on IHL and on contemporary legal frameworks.

Contemporary impact and influence

The prohibition on the use of expanding bullets in international conflicts, as codified in the Hague Declaration, has had a significant impact in later IHL treaties and legal instruments.Footnote ¹⁰⁶ This prohibition differed from the 1868 St Petersburg Declaration, which only prohibited projectiles of less than 400 grams that were either explosive or charged with inflammable substances.Footnote ¹⁰⁷ The Hague Declaration was only binding on the contracting powers in the case of a war between two or more of them and ceased to be binding if the belligerents were to be joined by a non-contracting power; nevertheless, it represented the first time this type of ammunition had been subject to IHL. It has since passed into general international law and is widely regarded as being part of international customary law.Footnote ¹⁰⁸ It constitutes Rule 77 of the International Committee of the Red Cross (ICRC) Customary Law Study and, as such, is widely regarded as being applicable to all States in international and non-international armed conflicts.Footnote ¹⁰⁹

The prohibition on the use of expanding bullets in IHL is linked to the idea of unnecessary suffering and superfluous injuries. The basis for this prohibition, like the prohibition on exploding bullets contained in the 1868 St Petersburg Declaration, is the idea that they were designed to cause unnecessary suffering or superfluous injuries upon impact.Footnote ¹¹⁰ These ideas are not exclusive to expanding bullets. Their prohibition was built upon the array of motivations that habitually underlie weapons prohibitions: that is, they were perceived as going against “prevailing criteria of honour, fairness, ethics, morality and so on, or because they were more devastating than need be”.Footnote ¹¹¹ The prohibition on expanding bullets in international conflicts, together with its associated norm, incorporates all of these criteria, which, together with the bullets’ perceived unfairness, illegitimized their use in international conflicts.Footnote ¹¹² The Hague Declaration has also held considerable influence on contemporary international criminal law, with the 1998 Rome Statute of the International Criminal Court standing out in this regardFootnote ¹¹³ – this treaty mirrors the Hague Declaration’s language and states within Article 8(2)(b) that the term “war crimes” refers to:

Article 8(2)(e) expands this prohibition to armed conflicts of not an international character following the Rome Statute’s 2010 Review Conference and the adoption of Resolution RC/Res.5.Footnote ¹¹⁵

The ethical motivations underlying the prohibition on the use of expanding bullets are akin to those that led to early prohibitions on the use of poison in war: there is no military utility in putting poison in projectiles so that neutralized soldiers die an agonizing death.Footnote ¹¹⁶ The suffering caused by these weapons made their use in combat seem fundamentally different. Though technologies were not regarded as immoral in and of themselves and their moral value was understood in terms of how they were used, expanding bullets did not follow this understanding. The Hague Declaration instead took “the form of a more absolute prohibition in that any kind of first use of such weapons was to be regarded as unacceptable”.Footnote ¹¹⁷ This is the core idea that nineteenth-century IHL treaties used to build their restrictions on the use of certain weapons in international conflicts, which aimed to ban the use of inhumane weapons that caused excessive or indiscriminate injuries.Footnote ¹¹⁸

Contemporary military manuals also reflect the prohibition on the use of expanding bullets, with Australia, the United Kingdom and Canada openly condemning their use in combat. For Australia, expanding bullets come under the prohibition of weapons that are calculated or modified to cause unnecessary suffering.Footnote ¹¹⁹ The United Kingdom’s Manual of the Law of Armed Conflict also reflects this idea and emphasizes the unnecessarily serious injuries caused by bullets that expand or flatten easily in the human body.Footnote ¹²⁰ Canada’s Joint Doctrine Manual on the Law of Armed Conflict, meanwhile, prohibits the use of expanding bullets on the grounds that they are indiscriminate in their effect.Footnote ¹²¹ The similarities of the prohibitions articulated in these military manuals, both between each other and to the IHL prohibitions detailed above, stand out, particularly through their emphasis on expanding bullets’ indiscriminate effects or the unnecessary injuries and suffering they cause.

The US Law of War Manual (US Manual) differs prominently from these prior examples. The US Manual emphasizes the importance of the law of war in US military practice. The law of war is of fundamental importance to the United States’ armed forces; it is “part of who we are” and linked with both President Lincoln’s Lieber Code and George Washington’s decree that the Revolutionary War was to be carried out in a way that was agreeable to the rules of humanity.Footnote ¹²² Despite this, the US Manual holds that expanding bullets are not necessarily unlawful: “The law of war does not prohibit the use of bullets that expand or flatten easily in the human body. Like other weapons, such bullets are only prohibited if they are calculated to cause superfluous injury.”Footnote ¹²³ The fact that expanding bullets can cause superfluous or unnecessarily severe injuries is not, therefore, considered an inherent characteristic of this type of bullet; instead, the US Manual questions whether expanding bullets always cause superfluous or unnecessarily severe injuries and accepts a ban on those that do cause such wounds. The US Manual references Captain W. Crozier’s objections at the 1899 Hague Conference – that expanding bullets were condemned “by designed implication, without even the introduction of any evidence against it, the use of a bullet actually employed by the army of a civilized nation” – in one of its footnotes.Footnote ¹²⁴

The US Manual’s position on expanding bullets is particularly significant when contrasted with the military manuals of the United Kingdom, Canada and Australia. The United States is not a party to the 1899 Hague Declaration due to how “evidence was not presented at the diplomatic conference that expanding bullets produced unnecessarily severe or cruel wounds”.Footnote ¹²⁵ The US Manual also considers the Hague Declaration’s prohibition on expanding bullets not to be a part of international customary law:

The US Manual also highlights expanding bullets’ ineffectiveness due to technical and military reasons, such as safety and the potential of weapon malfunction, and how this has led to a lack of use.Footnote ¹²⁷ Taken together with the points above, this is said to support “the conclusion that States do not regard such bullets are inherently inhumane or needlessly cruel”.Footnote ¹²⁸ This conclusion is also applied to the Rome Statute of the International Criminal Court, which “has been interpreted by States only to criminalize the use of expanding bullets that are also calculated to cause superfluous injury and not to create or reflect a prohibition against expanding bullets as such”.Footnote ¹²⁹ It is these facts that lead the US Manual to conclude that “this crime only applies to expanding bullets that are also calculated to cause superfluous injury and does not create or reflect a prohibition against expanding bullets as such”.Footnote ¹³⁰ The differences between the conclusions in the US Manual and the UK, Canadian and Australian military manuals are thus notable, particularly when juxtaposed with the treaties examined above.

Contemporary defences of the use of expanding bullets in international armed conflicts foreground the military utility of expanding bullets remarkably similarly: using expanding bullets, these arguments hold, is necessary to stop threats or enemies that may otherwise wound or kill large groups of people. Berry’s hypothetical scenario involving the use of expanding bullets to defend soldiers from suicide bombers highlights this idea.Footnote ¹³¹ Some American operators, he notes, “complained that the M855 was not effective at close ranges, where most urban combat engagements occur, and that a different bullet was required for such combat”.Footnote ¹³² This argument is reminiscent of the British defence of expanding bullets at the 1899 Hague Conference: normal bullets were “not sufficient to place a determined, fanatical opponent hors de combat”.Footnote ¹³³ In such situations, lethal force – regardless of how tragic the necessity for it may be – is a requirement rather than the mitigation of a risk.Footnote ¹³⁴ These defences appeal to the utility of expanding bullets when defending civilians or soldiers from attackers that need to be stopped immediately; in other words, they appeal to the need to use expanding bullets due to moral and ethical reasons which take precedence over the norm associated with the use of such bullets in conflict.

Having established the status of expanding bullets under IHL, we will now bring the different threads explored in this article together in a conclusion that highlights how norms are more nuanced than conventionally thought and can be linked to national interests.