Ukraine Symposium – The Kerch Strait Bridge Attack, Retaliation, and International Law

For some time, Ukrainian forces have threatened to attack the 12-mile Kerch Strait Bridge that links Russia and the Crimean Peninsula. Russia built the bridge following its 2014 seizure and illegal annexation of Crimea. It is of symbolic value for both countries, a sign of occupation for Ukraine and of the (claimed) expansion of Russian borders for its enemy. Indeed, President Putin marked the 2018 opening of the bridge by driving a truck over it.

The Kerch Strait Bridge is also of practical and strategic value. The bridge, which includes both vehicle and rail lines, is a major conduit for goods destined for the civilian population of Crimea and occupied southern Ukraine. It also serves as a key “line of communication” for Russian forces because, among other things, it allows resupply and reinforcement of Russian forces fighting in the Kherson and Zaporizhzhia regions, where Ukrainian forces continue their offensive.

On 8 October, around 6 in the morning, Ukraine made good that threat when an explosive device—possibly a truck bomb—caused a section of the bridge to collapse and ignited tanker cars on the rail line. President Putin labeled the attack a “terrorist act,” blamed the Ukrainian “special services,” and announced that “to leave such acts without a response is simply impossible.” That response, which continues, involves large-scale missile and armed drone attacks, most of which have targeted Ukrainian civilian infrastructure in populated areas, including Kyiv.

This post surveys the legal issues raised by the attack and the Russian response. We conclude that while the attack on the bridge did not violate international law, much of the Russian response did.

Bridges as Military Targets

The targeting of bridges has long been controversial, raising issues of distinction (whether bridges are military objectives or civilian objects) and proportionality (even if they are military objectives, whether the expected harm caused to the civilian population by the destruction of a bridge is excessive in light of the military advantage anticipated). For instance, in previous conflicts like the 1999 NATO Operation Allied Force air campaign against the Federal Republic of Yugoslavia and Israel’s 2006 Operation Change Direction in Lebanon against Hezbollah, the scope of targeting bridges beyond the area of active hostilities has been questioned. Following Operation Allied Force, the Air Component Commander observed, “I felt that on the first night the power should have gone off, and major bridges around Belgrade should have gone into the Danube, and the water should be cut off so the next morning the leading citizens of Belgrade would have got up and asked, ‘Why are we doing this? and asked Milosevic the same question.” The comment ignited a firestorm of criticism, and rightly so as a matter of law.

In an accurate reflection of customary international law, Article 52(2) of Additional Protocol I, to which both Russia and Ukraine are Party, defines military objectives as “those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military of advantage.” That bridges sometimes qualify as lawfully targetable military objectives under international humanitarian law (IHL) is self-evident. The question is when they do so.

Among IHL experts, there is debate over whether bridges qualify by virtue of their nature, location, purpose, or use under Article 52(2). Yoram Dinstein has suggested, “When constructed for the engineering needs of major highways and rail tracks, they are surely integrated in the overall network: like the roads and the tracks that they serve, they constitute military objectives by nature” (p. 115). Examples include bridges on the U.S. interstate highway system or Germany’s autobahn. For him, other bridges should be assessed based on whether they are being used or will be used (purpose) for military ends, or whether their location is of military significance. By the Dinstein approach, the Kerch Strait Bridge qualifies as a military objective by nature because it is a key bridge on a major line of communication in territory controlled by Russia.

The alternative view, which we support, is that bridges must qualify by their use, purpose (future use), or location. Except in rare cases, such as a bridge on a military installation, they do not fall into the category of inherently military objectives, such as military facilities and equipment.

Nevertheless, the Kerch Strait Bridge is a military objective based on both its use and location. Any military use renders an object a military objective even if it also serves civilian purposes, and this bridge has been regularly used as an essential line of communication for Russian forces since it was built (e.g., to supply occupation forces in Crimea and, presently, to support operations in the south of Ukraine). It also qualifies as a military objective based on location, for it permits resupply and reinforcement from Russia to transit through Crimea to the occupied territory where heavy fighting is underway; interfering with its use has the potential to impact ongoing combat operations significantly.

Targeting Bridges, Proportionality, and Precautions

Even when a bridge qualifies as a military objective, an attack on it must comply, inter alia, with the IHL rule of proportionality found in Additional Protocol I, Articles 51 and 57, and customary law. That rule prohibits “an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.”

Assessing proportionality is among the most challenging tasks an attacker faces, for no ready formula exists into which the anticipated military advantage of a strike and any expected collateral damage may be plugged. In this case, however, it appears clear that the attack was proportionate. Damage to the bridge would reasonably have been expected to affect both Russian military operations throughout the southern theatre of operations and occupation military activities within Crimea. Tragically, the attack reportedly resulted in three civilian deaths. But given the military advantage the attackers could reasonably have anticipated from cutting the bridge, e.g., the disruption to Russian supply lines, the attack was proportionate. And damage to the bridge itself does not qualify as collateral damage in the assessment, even though it is used for civilian purposes. This is because once an object is used for both military and civilian ends, it is characterized as a military objective in its entirety.

We acknowledge that the attack could also have been expected to affect the supply of the civilian population and disrupt civilian activities ranging from personal travel to commercial activities. However, these effects do not factor into the proportionality analysis, which is limited in the text of the rule itself to loss of life, injury, and damage to civilian objects. Interference as such with the use of a civilian object generally does not qualify as collateral damage unless the foreseeable consequences of that loss include these enumerated effects. This would likely only be the case if the attack caused starvation and sickness, which was unlikely in this case. There is also no evidence that the bridge’s destruction was designed to starve civilians in Crimea, which would be prohibited by Article 54 of Additional Protocol I.

Even when an attack is against a military objective and expected collateral damage is not excessive to the anticipated military advantage, an operation must still comply with the obligation to take precautions in attack to minimize harm to civilians and civilian objects. This requirement is outlined in Article 57 of Additional Protocol I, which, as noted, reflects customary law.

Here, the bridge was attacked at six in the morning when significant civilian loss was unlikely, a conclusion supported by the small number of civilian casualties. Whether the time of the attack reflects an intentional effort to comply with the requirement to take precautions in attack is unknown. Still, even if not, it does not appear that any alternative means of destroying the bridge that would have had a lesser effect on civilians was available to the attackers.

The Identity of the Attacker and Attribution

The discussion in this post, and the way the attack on the Kerch Strait Bridge has generally been presented in the media, has assumed that Ukrainian State agents committed the attack. But at this time, it remains unclear who attacked the bridge. Speculation ranges from Ukrainian special forces to non-State individuals or groups; the (current) Russian official version is that Ukrainian secret services damaged the bridge using a truck bomb.

Members of the armed forces are obviously entitled to engage in attacks against military objectives like the Kerch Strait Bridge. It is sometimes asserted that IHL prohibits civilians from doing so, but that is wrong. Under IHL, an individual who “directly participates in hostilities” loses protection from attack for such time as that individual is engaged in the activity (Article 51(3) and customary law). Moreover, direct participants do not factor into proportionality calculations or assessments of possible precautions in attack. And they lack combatant immunity from prosecution for acts violating domestic law. However, they do not violate any IHL rule by mere participation. Only those acts of direct participation that otherwise violate IHL rules (like perfidy) are prohibited under IHL. And, of course, if there was a truck bomb and a Ukrainian agent drove the truck, there is no IHL prohibition on undertaking dangerous, even suicidal, operations.

Ukrainian officials have not so far assumed responsibility for the attack on the bridge. While attribution of the attack to Ukraine remains the most logical possibility, other options cannot be conclusively excluded at this time. For example, it is possible that the bridge was destroyed by a non-State group operating with the assistance—but not necessarily under the instruction, direction, or control—of Ukrainian secret services. In such a case, Ukraine would not be responsible under the law of State responsibility (see art. 8 of the Articles on State Responsibility) for the attack should it amount to a breach of international law (see discussion below). Absent attribution, a breach of an international obligation does not amount to an “internationally wrongful act.”

The Death of the Truck Driver

It is possible that the explosion on the bridge was not caused by a truck bomb but by some other means (see more BBC and Meduza reports), even if a truck bomb remains the most plausible option at this time. But assuming a truck bomb caused the explosion, what if the truck was driven by an unsuspecting civilian, with the blast triggered remotely once the truck was on the bridge?

There is no conclusive evidence that is what occurred, although media reports suggest that the truck’s driver was 51-year-old Makhir Yusubov, a relative of its owner with no apparent ties to Ukraine. If so, it seems unlikely that Yusubov wittingly participated in the scheme to destroy the bridge, i.e., was aware that he was transporting explosives and chose to detonate them at the cost of his own life.

Suppose Ukrainian agents manipulated Yusubov into driving the truck bomb onto the bridge, something that, we repeat, is yet to be established. Doing so would, in our view, constitute an attack against a civilian in violation of the prohibition set forth in Article 51(2) of Additional Protocol I and customary law, for individual civilians may not be made the “object of attack.”  This is so even though the further desired effect of the operation is on a military objective such as the Kerch Strait Bridge. In other words, his death would not bear on a possible violation of the proportionality rule but instead violate the principle of distinction. He would have been the unwilling instrument of delivering the weapon that would inevitably have caused his own death and was, in that sense, made the object of the attack as much as the bridge itself. The scenario here would be comparable to one in which (say) Russian soldiers strapped explosives onto a Ukrainian civilian and sent him against Ukrainian combatants, who are lawful military targets. In both scenarios, a civilian is being used to deliver a kinetic attack in which that civilian would inevitably perish … and was accordingly equally the object of the attack.

A similar result would be reached if the death of the driver (ostensibly caused by Ukrainian agents) was evaluated from the standpoint of the human right to life, as articulated in Article 2 of the European Convention on Human Rights, which Ukraine is bound to apply. Using an unwilling or unwitting human being as the means for achieving an otherwise “legitimate aim” (destruction of a military objective) when the operation would inevitably result in the person’s death cannot be squared with the “absolute necessity” requirement under international human rights law (IHRL) for lawful, justified taking of human life.

The Russian Response

Russia has reacted to the Kerch bridge attack by firing cruise missiles and flying armed drones into population centers. It may be the case that some of the strikes amount to the targeting of military objectives, such as electrical generation facilities and other infrastructure that serves both civilians and the armed forces (dual-use targets). Regarding such strikes, legal issues would thus arise only concerning the rule of proportionality and the requirement to take precautions in attack. But a full evaluation of these strikes in light of these rules would require some explanation from Russia as to why specific targets were chosen and what military advantage was anticipated from these attacks. No such explanation has been forthcoming.

However, it appears clear to us that the Russian forces are either firing indiscriminately into populated areas, thereby violating the prohibition on indiscriminate attack (Article 51(4) of Additional Protocol I and customary law), or directly targeting civilians and civilian objects. Moreover, the Russian strikes appear to violate the prohibition on attacks, “the primary purpose of which is to spread terror among the civilian population” (Article 51(2) of Additional Protocol I and customary law). These conclusions are reasonable inferences from the number of attacks, the nature of the objects hit (e.g., the destruction of a pedestrian bridge in Kyiv with no discernible military use), and the number of civilians killed and wounded. Further support comes from the clear statement by Putin that the attacks were in retaliation for the “terrorist” attack on the Kerch Strait Bridge.

This raises the question of whether such attacks are permitted as a reprisal. They are not. Reprisals are violations of IHL designed to coerce an enemy to desist from its own IHL violations. Even for States like the United States that maintain the position that certain reprisals are lawful, they are considered extreme measures subject to significant limitations (see U.S. Department of Defense Law of War Manual, § 18.19). But those limitations need not detain analysis here for two reasons.

First, a violation of IHL is the condition precedent to taking reprisals. Despite Putin’s characterization of the attack on the Kerch Straight Bridge as “terrorism,” it was, as we explained above, a lawful attack, on the assumption that it was attributable to Ukraine in the first place. Second, and more importantly, even if the attack on the Kerch Bridge was unlawful under IHL, e.g., because the bridge should (contrary to our analysis) be considered a civilian object, this could not justify Russia conducting attacks on Ukrainian civilians and civilian objects. In particular, Russia and Ukraine are both parties to Additional Protocol I, which categorically prohibits the taking of reprisals against both civilians and civilian objects (Articles 51(6) and 52(1) of Additional Protocol I, respectively).

Conclusion

To sum up, assuming Ukrainian agents conducted the operation against the Kerch Strait Bridge, the attack was plainly lawful under IHL. The bridge was a military objective because Russian armed forces regularly used it for military purposes. And the attack was not disproportionate, i.e., the expected incidental loss of civilian life was not excessive compared to the military advantage that Ukraine could anticipate from damaging the bridge. Further, the attack appears to have been conducted in a manner designed to minimize harm to civilians, as is required by the rule on taking precautions in attack. Finally, the attack was not an “act of terrorism” in any international legal sense of the word; in particular, it was clearly not done for the purpose of spreading terror in the civilian population.

The only possible qualification regarding the lawfulness of the attack on the bridge relates to the death of the driver of the truck. If the bridge was destroyed by a truck bomb in a Ukrainian-controlled operation, as Russia alleges, and if the truck driver was not a willing participant in the operation, the use of this individual to deliver a weapon deadly to himself violated both IHL and IHRL. We reiterate, however, that at this time, the circumstances of the means used to damage the bridge remain unclear, and we would also note that any unlawfulness of the killing of the truck driver has no bearing on the lawfulness of the attack on the bridge itself.

Russia’s ongoing attacks on numerous targets in Ukraine are, by contrast, undoubtedly unlawful. Although detailed facts about each Russian attack over the past few days are unavailable, the overall pattern indicates that civilian objects and civilians are being hit deliberately or indiscriminately. They, therefore, violate the principle of distinction. Even those few that may have been directed at a military objective raise serious questions about compliance with the rule of proportionality and the requirement to take precautions in attack (as in launching strikes during morning rush hour in Kyiv, which compares poorly to the timing of the attack on the Kerch Bridge).

And as we explained, even if somehow the attack on the Kerch Strait Bridge is regarded as unlawful, Russia would not be entitled to respond to that purported illegality by launching reprisal attacks against civilians and civilian objects. Nor may Russia lawfully respond to an “act of terrorism” by itself intentionally spreading terror in the civilian population of Ukraine, which is what it appears to be doing, if with little apparent success.

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Marko Milanovic is Professor of Public International Law and Co-Director of the Human Rights Law Centre at the University of Nottingham School of Law. He is co-editor of EJIL: Talk!, the blog of the European Journal of International Law, as well as a member of the EJIL’s Editorial Board.

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.

Photo credit: Rosavtodor.ru