Ukraine Symposium – Dirty Bombs and International Humanitarian Law

On October 23, Russian Defense Minister Sergei Shoigu made separate calls to the Defense Ministers of France, Turkey, the United Kingdom, and the United States. In them, Shoigu claimed that Ukraine intended to conduct a false-flag operation with a “dirty bomb” in order to accuse Russia of using a weapon of mass destruction. Russian media has echoed the accusation. France, the United States, and the United Kingdom quickly released a joint statement in which they “made clear that we all reject Russia’s transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory” and that they “remain committed to continue supporting Ukraine’s efforts to defend its territory for as long as it takes.”

But Russia continues to level the accusation, most recently in a letter to the United Nations that announces it will raise the matter in a closed Security Council session. In the letter, Russia’s U.N. Ambassador warns, “We will regard the use of the dirty bomb by the Kyiv regime as an act of nuclear terrorism.” Ukraine’s President Zelensky characterized the allegation as a sign that Moscow plans a tactical nuclear attack, using the false flag dirty bomb attack to shift the blame to Ukraine. In that regard, the U.S. State Department has warned, “There would be consequences for Russia whether it uses a dirty bomb or a nuclear bomb.”

The premise that the claims could serve as a pretext for an escalation of Russian operations is consistent with recent Russian tactical nuclear weapons saber-rattling. But the Institute for the Study of War deemed it unlikely that Russia itself was preparing an imminent dirty bomb false flag attack. Instead, the organization believes Shoigu’s assertion is a continuation of an information campaign in which “[t]he Kremlin has repeatedly claimed that Western states will help Ukraine conduct a false-flag WMD attack.” According to the Institute, Shoigu’s calls were “likely intended to intimidate Western states into cutting or limiting support for Ukraine as Russia faces continued military setbacks and the likely loss of western Kherson by the end of the year.”

Hopefully, the Institute is correct regarding the likelihood of a dirty bomb attack. And most Western supporters of Ukraine appear to see the claims for what they are – pure disinformation. But the allegations do raise the question of the international humanitarian law (IHL) surrounding so-called “dirty bombs.” This post teases loose those rules that would govern their use by either side…and those which would not.

Dirty Bombs

A fair degree of confusion surrounds the label “dirty bombs,” a weapon that falls into the category of “radiological dispersal devices” (RDD). Dirty bombs combine conventional explosives like dynamite with radioactive material, such as that used at hospitals, research laboratories, and nuclear power stations. The explosive force of detonation disperses the radioactive material, which is typically reduced to powder or pellets. Such weapons are relatively easy to build.

The amount of radiation released would usually not be enough to prove lethal. As noted by the U.S. Nuclear Regulatory Commission (NRC), the immediate health effects of a dirty bomb would  “likely be minimal,” although those effects would be determined by: the degree of radiation that the body absorbs; the type of radiation (gamma, beta, or alpha); the individual’s distance from the source of the radiation; whether the radiation is absorbed by the skin, inhaled, or ingested; and how long the individual is exposed.

Similarly, the Centers for Disease Control concludes, “[o]nly people very close to the blast site would be exposed to enough radiation to cause immediate serious illness. However, the radioactive dust and smoke can spread farther away and could be dangerous to health if people breathe in the dust, eat contaminated food, or drink contaminated water.” Usually, the explosive blast poses the most significant risk to individuals in the vicinity of detonation, although a very large bomb could cause considerable radiation illness, even multiple deaths. 

Dirty bombs typically are not designed to cover large areas, for, as the NRC points out, as the “radioactive material spreads, it becomes less concentrated and less harmful.” Similarly, the BBC explains, “if the particles are too fine or released into strong winds, they will scatter too widely to do much harm.” The use of a dirty bomb could, however, contaminate property, thereby rendering the affected area unusable until decontaminated.

Instead, the key to a dirty bomb is its psychological impact from fear of being, or having been, exposed to radiation. In part, this is because radiation cannot be seen, smelled, tasted, or felt. Thus, the NRC concludes that a dirty bomb “is not a ‘Weapon of Mass Destruction’ but a ‘Weapon of Mass Disruption,’ where contamination and anxiety are the terrorists’ major objectives.” Simply put, they are terror weapons that have little conventional utility on the battlefield.

No State has developed the weapon for conventional use by its armed forces. Nor have terrorists successfully employed one despite some attempts to do so.

The Law

Dirty bombs implicate numerous IHL rules, although, as will be seen, it is important not to jump to conclusions regarding the applicability of certain rules.

Attacking Civilians and Civilian Objects

There is no question that if either Russia or Ukraine employs a dirty bomb directly against civilians or civilian objects, the operation will violate the treaty (Additional Protocol I, arts. 51(2) and 52(1)) and customary law (Customary IHL study, rules 1 and 7) prohibitions on attacking them, for these rules apply regardless of the means (weapon) or method (tactic) of warfare employed. Yet, in discussions with colleagues, the legal characterization of a theoretical Ukrainian false flag use has surfaced. The question is whether it would be an IHL violation for Ukraine to target its own people.

IHL targeting rules do not distinguish civilians based on nationality. But that does not mean that every killing of a civilian qualifies as an unlawful attack on civilians under IHL. Particularly relevant in this regard is the issue of motive. Dick Jackson and several of his colleagues explained that to qualify as an “attack” subject to the IHL rules governing them, there must be a motive to cause harm to the adversary or other persons in the conduct of hostilities. I would emphasize that this requires nexus to the conflict. That is the case here, for a Ukrainian false flag attack would be designed to affect Russian military operations by dramatically enhancing military support for Ukraine. Ukraine would not conduct the operation but for its impact on the ongoing hostilities.

Jackson and his colleagues also point to the legal issue of control, suggesting that “acts of violence directed at persons or objects under the dominion and control of a belligerent—to include persons who are hors de combat—do not qualify as attacks.” But they are quick to note, and correctly so, that control over a person is not to be equated with control over territory. The former is exemplified by killing an individual in detention, and the latter by targeting individuals living in an area under the attacking party’s control, as would be the case in Ukraine.

Accordingly, in my view, a theoretical attack by Ukrainian forces on Ukrainians in order to secure military support would be no less an attack on them than a Russian use of a dirty bomb against those same civilians. Those involved would also be committing murder under Ukrainian domestic law. Of course, if Russian forces conducted a dirty bomb attack in order to blame it on Ukraine as a pretext for escalation, the same result would hold. This is true regardless of whether the attack occurred in Ukrainian or Russian-controlled territory.

Proportionality and Precautions in Attack

Assuming solely for the sake of analysis that either side used a dirty bomb against a military objective, the rule of proportionality and the requirement to take precautions in attack would be triggered (Additional Protocol I, arts. 51(5)(b), 57; Customary IHL study, rules 14 and 15). By the former, any resulting expected incidental damage to civilian objects or injury to civilians would have to be considered to assess whether it would be excessive relative to the anticipated concrete and direct military advantage of the strike. In the collateral damage calculation, I would include the fact that an object is rendered unusable due to being irradiated. Any civilian radiation sickness likewise would qualify as injury. And as with directly targeting them, the fact that Ukrainian nationals and objects would be the victims of incidental injury in a Ukrainian attack would not preclude their inclusion in the requisite proportionality calculation.

More problematic legally in a dirty bomb attack is the requirement to take precautions to minimize collateral damage, which would include those same radiation effects. Of particular note, there is a requirement to choose among means and methods of warfare to do so, as long as no potential military advantage is sacrificed (Additional Protocol I, art. 57(2)(a)(ii); Customary IHL study, rule 17; DoD Law of War Manual, § 5.11).

Because dirty bombs are merely radioactive material added to an explosive device, the only way such a bomb could meet the requirement is if the use of radioactive material enhanced the achievement of a valid military purpose. But because explosive force is the primary effect caused by such weapons, that is unlikely to be the case. And the fact that the weapon’s use will cause civilian fear or serve as a pretext for future military operations does not qualify as military advantage for the purposes of the rule. Only if the area denial consequence of the radiation affected enemy military operations in a meaningful way could the use of a dirty bomb pass muster. Thus, in most conceivable scenarios, using a dirty bomb would violate the rule requiring precautions in attack.

Indiscriminate Attack

Depending on how the dirty bomb attack was conducted, it also could violate the prohibition on indiscriminate attacks (Additional Protocol I, art. 51(4); Customary IHL study, rule 11; DoD Law of War Manual, § 5.5). This rule prohibits attacks that are not directed at specific military objectives or combatants, as in not being aimed, and those that cannot be so directed. There is nothing in a dirty bomb that makes violation more likely on these bases.

Instead, it is more likely that a dirty bomb attack would be indiscriminate on the basis that it “employ[s] a method or means of combat the effects of which cannot be limited …; and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction” (Additional Protocol I, art. 51(4)(c)). Because a dirty bomb uses radioactive powder to disperse radiation, it is susceptible to wind. Should a bomb be large enough to release a significant amount of radiation that places civilians at risk in unpredictable winds, the attack would be indiscriminate, even if it targets a military objective. Although hypothetically possible, this would be unlikely because wind causes radiation to dissipate. Moreover, if the civilian effects could be reasonably estimated because, for instance, wind direction is known, the issue would be proportionality, not indiscriminate attack.

Terror Attack

In a reflection of customary law (Customary IHL study, rule 2), Article 51(2) of Additional Protocol I prohibits “acts or threats of violence the primary purpose of which is to spread terror among the civilian population” (see also  DoD Law of War Manual, § 5.2.2). As there is only limited military utility in including radioactive material in a dirty bomb, it is a paradigmatic terror weapon. There is little rationale for its use by Russia (or Ukraine) beyond terrorizing the population, thereby satisfying the primary purpose requirement.

The fact that the ultimate purpose might be other than to spread terror among the civilian population would not deprive such a use of its terror attack status. For instance, although a Russian false flag attack might be designed to provide a basis for escalation, it could do so only because of the local terror and international shock the attack would generate. Similarly, even if the false Russian claims that Ukraine will use a dirty bomb in a false flag operation to further ostracize Russia were true (they obviously are not), the immediate purpose would be to cause fear and shock as the triggers for achieving that end.

Note that the prohibition extends to threats of violence designed to terrorize. I believe Russia has already violated this prohibition by raising the specter of dirty bomb attacks. There is no requirement that the party issuing the threat in question intends to carry it out. Thus, even if the Institute for the Study of War is correct that Russia does not intend to employ a dirty bomb, the fact that it is working hard to create the impression that such an attack will occur ensures the requisite intent to terrorize is satisfied. Moreover, I would suggest that although the threat being issued is that of Ukrainian violence rather than Russian, this does not preclude a finding of a Russian violation. The effect of the claim remains the terrorization of the target civilian population.

Protection of the Natural Environment

The fact that dirty bombs involve the spread of radiation raises the issue of environmental impact. In my view, harm to the natural environment can qualify as collateral damage subject to the rule of proportionality and the requirement to take precautions in attack to minimize harm to civilian objects (see discussion above and my analysis in Green War). However, for Parties to Additional Protocol I, like Russia and Ukraine, the environment is subject to “special protection” under Articles 35(3) and 55 of Additional Protocol I.

The former provides that “[i]t is prohibited to employ methods or means of warfare which are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment.” Although the latter provision sets forth identical criteria, it ties the prohibition to its impact on the civilian population’s well-being:  

Care shall be taken in warfare to protect the natural environment against widespread, long-term and severe damage. This protection includes a prohibition of the use of methods or means of warfare which are intended or may be expected to cause such damage to the natural environment and thereby to prejudice the health or survival of the population.

In most cases, the environmental consequences of a dirty bomb’s use would not satisfy the three cumulative conditions. For instance, the term “longstanding,” as used in the Protocol, refers to harm lasting decades (ICRC Commentary, ¶ 1452). That would not be the case in most dirty bomb attacks. And although the Commentary contains little guidance regarding the other two criteria, the 2022 U.S. Army Judge Advocate General’s School Operational Law Handbook suggests the term widespread “probably means several hundred square kilometers.” Again, this is unlikely in most cases for the reasons explained above. And also as explained, most effects would not merit being labeled “severe” in the plain meaning of the term.

Poison Weapons 

Poison weapons have been prohibited since ancient times in armed conflict. In modern times, the prohibition has appeared in the Lieber Code (art. 70), 1899 and 1907 Hague Regulations (art. 23(a)). The ICRC properly characterizes it as customary law (Customary IHL study, rule 72), as did the International Court of Justice (ICJ) in its Nuclear WeaponsAdvisory Opinion (¶¶ 80-82). And the DoD Law of War Manual prohibits their use (§ 6.8).

However, to violate the IHL prohibition on poisoning, the consequences of its use should be severe. For instance, the poisons encompassed in the prohibition are those “substances that cause death or disability with permanent effects when, even in small quantities, they are ingested, enter the lungs or bloodstream, or touch the skin,” according to the DoD Law of War Manual (§ 6.8.1). Similarly, in the analogous context of war crimes (individual instead of State responsibility), Articles 8(2)(b)(xvii) and (e)(xiv) of the Rome Statute of the International Criminal Court prohibit employing poison weapons, but only if the “substance was such that it causes death or serious damage to health” (Elements 2).

The prohibition could encompass poisoning by radiation. Consider the 2006 poisoning of Alexander Litvinenko with polonium-210, which caused a lethal case of acute radiation syndrome, an act for which the European Court of Human Rights found Russia responsible in Carter v. Russia. It is certainly possible that a dirty bomb used during the war in Ukraine could be intended to cause harm of the requisite severity. But as such weapons generally are conceived, the primary harmful effect on persons is the explosion, and the type of harm suffered by individuals due to radiation exposure usually is not severe. Each case would have to be evaluated on its merits, but it cannot be said that a dirty bomb necessarily qualifies as a poison weapon.

Superfluous Injury and Unnecessary Suffering

The prohibition on using weapons causing superfluous injury and unnecessary suffering, which the ICJ labeled a “cardinal principle” of IHL in its Nuclear Weapons advisory opinion (¶ 78), stretches back to the 1868 St. Petersburg Declaration. It subsequently appeared in the Hague Regulations of 1899 and 1907 [art. 23(e)] and 1977 Additional Protocol I (art. 35(2)). The ICRC correctly considers it a customary rule (Customary IHL study, Rule 70), and it is included in the DoD Law of War Manual (§ 2.3).

Employing a dirty bomb to deny the enemy use of an area would not violate the prohibition. But if used for the purpose of causing combatants suffering due to radiation poisoning that is additional to any harm caused them by the explosive effects of the weapon, the rule would be violated. Because dirty bombs would generally cause only low doses of radiation, it is unlikely that the weapons would be used for this reason. Instead, they are more likely to be employed to cause panic in the forces against which they are used. Unlike their use for the same purpose against civilians, terror attacks on combatants (or civilians directly participating in hostilities) are lawful.

Arms Control and Dirty Bombs

In 1979, the U.N. Committee (now Commission) on Disarmament agreed to include radiological weapons in the definition of “weapons of mass destruction.” The Soviet Union and the United States were, at the time, negotiating a treaty to govern the development, production, stockpiling, and use of other than nuclear weapons that could disseminate radioactive material. Unfortunately, the effort proved unsuccessful; a post-9/11 attempt to revive the matter in the U.N. Commission on Disarmament likewise failed (see generally Herbach).

Moreover, despite frequently being confused with them, dirty bombs are not nuclear weapons. Nuclear weapons employ fission or fusion to create a massive explosion; dirty bombs do not. In addition to the explosion, the use of a nuclear weapon releases large amounts of radiation over vast areas as irradiated debris spreads and exposure to a nuclear weapon’s radiation, unlike dirty bombs, can often cause severe illness and death. In that dirty bombs are not nuclear weapons, they are not encompassed in the prohibition on the use or threat of use in Article 1(d) of the Treaty on the 2017 Prohibition of Nuclear Weapons, to which neither Russia nor Ukraine are Party in any event.

Concluding Thoughts

It is very difficult to imagine circumstances in which any use of a dirty bomb would be lawful, for they are terror weapons, and IHL unequivocally bans violence, or threats of violence, designed to terrorize the civilian population. Moreover, because the attack would be unlikely to be directed at a military objective because that would diminish its presumptive intended psychological impact, the use of a dirty bomb would violate the rules prohibiting attacks on civilian and/or civilian objects.

But it must be cautioned not to “over-charge” any Russian use of a dirty bomb, for doing so will detract from the otherwise clear IHL violations such use would entail.  For instance, it is unlikely, albeit not impossible, that employing a dirty bomb would violate the special protection the environment enjoys under IHL or the prohibition on using poison. Additionally, although dirty bombs are sometimes confused with nuclear weapons in current public discourse, that is a mistake of law.

Despite this cautionary note, it is evident that Russia has thrown out the IHL rule book. Yet again, it is using offensive lawfare in a condemnable manner.

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Michael N. Schmitt is the G. Norman Lieber Distinguished Scholar at the United States Military Academy at West Point. He is also Professor of Public International Law at the University of Reading; Professor Emeritus and Charles H. Stockton Distinguished Scholar-in-Residence at the United States Naval War College; and Strauss Center Distinguished Scholar and Visiting Professor of Law at the University of Texas.

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