This article was first published on Just Security.

In the current armed conflict in Ukraine, Russian forces have relied heavily on two types of weapons that are notorious for the unacceptable and often unlawful harm they inflict on civilians. The weapons are cluster munitions, which have been banned by most countries in the world, and explosive weapons with wide area effects, which when used in populated areas are among the major causes of civilian casualties in contemporary armed conflict.

Attacks with these weapons have already killed and injured hundreds of civilians, turned buildings into rubble, and led to mass displacement. Judging by the experience of past conflicts, they will most likely also leave Ukraine with a legacy of harm that lingers long after active hostilities end.

Cluster Munitions

Cluster munitions, large weapons that contain dozens or hundreds of smaller weapons called submunitions, endanger civilians for two reasons. First, they have a wide area effect because they spread their submunitions over a broad footprint, commonly the size of a football field.  These submunitions cannot distinguish soldiers from civilians when used in populated areas. Second, many of their submunitions do not explode on impact, becoming de facto landmines that pose threats to civilians for months, years, or even decades after a conflict. These so-called “duds” are frequently detonated by children who think they are toys, farmers who hit them with their plows, or refugees who return home.

The immediate harm caused by cluster munitions has already been evident in Ukraine. Human Rights Watch (where I am a senior researcher) documented a strike by Russian forces near a hospital in Vuhledar in the Ukraine-controlled Donetska region on Feb. 24. A 9M79-series Tochka ballistic missile delivered a 9N123 cluster munition warhead, containing 50 submunitions. The attack killed four civilians and injured another 10, including six healthcare workers. It damaged a hospital building, an ambulance, and civilian vehicles.

Four days later, on Feb. 28, Russian forces launched 9M55K Smerch cluster munition rockets in three neighborhoods of Kharkiv, Human Rights Watch found. Each of these rockets, which are often fired in volleys of 12, carries 72 9N235 submunitions. The United Nations reported nine civilian deaths and 37 injuries in attacks across the city that day.

Russian forces launched Smerch and Uragan cluster munitions into the city of Mykolaiv on Mar. 7, 11, and 13, reportedly killing nine civilians in line at a cash machine on the last day alone, according to more recent Human Rights Watch research. Other organizations and journalists have also reported cluster munition attacks in Ukraine.

International humanitarian law (IHL)’s rule of distinction requires parties to a conflict to distinguish between civilians and combatants and between civilian objects and military objectives. The use of cluster munitions, at least where civilians may be present, violates this rule. Human Rights Watch and others argue they are inherently indiscriminate. At the time of attack, the wide-area effect of these weapons prevents them from distinguishing between combatants and non-combatants. In addition, the unexploded submunitions they leave behind makes them indiscriminate because their effects cannot be limited. Attacks using cluster munitions in populated areas may also violate the principle of proportionality, which prohibits attacks in which expected injury to civilians or damage to civilian objects is excessive in relation to anticipated military advantage.

The people who order or carry out cluster munitions attacks against civilians or civilian objects with criminal intent—that is, willfully or recklessly—are responsible for war crimes.

Due to the unacceptable harm cluster munitions cause and their indiscriminate nature, the 2008 Convention on Cluster Munitions bans their use, production, transfer, and stockpiling. Although Russia and Ukraine have not joined the treaty, 110 countries are party, including most NATO countries (although not the United States).

The convention also obligates each state party to “promote the norms it establishes and … make its best efforts to discourage States not party to this Convention from using cluster munitions.” In compliance with this provision, at least 15 states parties have condemned or expressed concern about Russia’s use of cluster munitions in Ukraine.

The president of the Convention on Cluster Munitions, which is currently the United Kingdom, along with the NATO Secretary-General, the UN High Commissioner for Human Rights, and the European Union have also condemned the use of cluster munitions in Ukraine.

Explosive Weapons in Populated Areas

While cluster munitions are especially horrific for civilians, they are just one type of explosive weapon. The broader category of explosive weapons, which encompasses artillery shells, mortar rounds, rockets, missiles, enhanced blast (aka thermobaric) weapons, and aerial bombs, among others, has caused the bulk of the conflict-related damage in Ukraine.

The use of explosive weapons in populated areas has grave humanitarian consequences both during and after attacks. Those effects are magnified when the weapons have wide area effects because: they have a large blast or fragmentation radius; they are inaccurate; they deliver multiple munitions at once (e.g., cluster munitions); or they have a combination of the above.

Russia’s bombing and shelling of Ukraine’s cities and towns has taken a physical and psychological toll on the civilian population. According to Human Rights Watch, Russian artillery shelling and airstrikes killed or injured  more than 450 civilians in the city of Kharkiv in the first 11 days of the conflict. The attacks have also leveled homes, apartment buildings, and other primarily civilian structures and infrastructure, and damaged the environment.

The costs of this method of war, however, extend beyond its direct effects. The use of explosive weapons with wide-area effects in populated areas also causes indirect and reverberating effects. The destruction of infrastructure can interfere with essential services and in turn infringe on an array of human rights.

In 2016, I co-authored an in-depth report on the effects of explosive weapons’ use on health care in the earlier conflict in eastern Ukraine, which was published by Harvard Law School’s International Human Rights Clinic (where I teach) and PAX. We found, for example, that damage to power plants and communication lines seriously affected hospitals and the provision of health care, and thus undermined the right to health. Such reverberating impacts will almost certainly be more severe in the current – much larger – conflict.

The use of explosive weapons in populated areas also exacerbates displacement. As of Mar. 18, more than three million people had fled Ukraine as a result of the conflict, according to the UN Refugee Agency (UNHCR). The attacks on urban centers with explosive weapons are one of the driving factors.

In a statement to the UN Security Council, a representative from the UN Office for the Coordination of Humanitarian Affairs (OCHA) noted that many of these effects were already being felt by Feb. 28. “As we all feared, civilians are already paying the price,” he said. “The scale of civilian casualties and damage to civilian infrastructure, even in these very early days, is alarming.”

Explicitly highlighting the dangers of the use of explosive weapons with wide-area effects, he continued, “Civilians will undeservedly suffer the most from these attacks on densely populated urban centres. . . .  And the longer this goes on, the greater the cost will be for civilians.”

Using  explosive weapons with wide-area effects in populated areas can be expected to result in indiscriminate attacks with a high loss of civilian life. The patterns of harm to civilians that these weapons cause, including their reverberating effects, are well documented and heighten concerns that attacks will also be disproportionate. In addition, the use of explosive weapons with wide area effects in populated areas is generally counter to the IHL duty to take all feasible precautions to minimize civilian harm. Those who are responsible for using explosive weapons unlawfully with criminal intent are committing war crimes.

While explosive weapons, unlike cluster munitions in particular, are not banned by any instrument of international law, countries have been working toward a political declaration that addresses the humanitarian consequences of their use in populated areas. The next round of negotiations of this Ireland-led process, which had been postponed by the Covid-19 pandemic, are now scheduled for April 6-8.

The events in Ukraine underscore how important it is for countries to include in the declaration a commitment to avoid the use of these weapons in populated areas. This political commitment, although non-binding, would set important standards for dealing with a deadly practice of modern war.

The concern regarding Russia’s use of explosive weapons in Ukraine’s urban centers from countries including Austria and Ireland, and as stated in the UN Human Rights Council resolution of Mar. 4, demonstrates the growing support for these standards.

Cease and Condemn

The horrific images and accounts emerging from Ukraine offer a glimpse of the immediate harm that Russian cluster munitions and explosive weapons are inflicting on Ukraine’s civilians. Documentation of the effects of these weapons in past conflicts suggest the harm will be long term.

To prevent furthering the humanitarian crisis, Russia should immediately cease the use of cluster munitions and avoid using explosive weapons with wide area effects in populated areas. Other countries and the United Nations should support documentation efforts to ensure domestic and international accountability for any violations of IHL and international human right law and in particular support the International Criminal Court’s Ukraine investigation.

Other states and the United Nations should also explicitly condemn the use of cluster munitions and explosive weapons with wide area effects in populated areas. Such focused criticism will not only increase pressure on Russia to change its practices in Ukraine. It will also strengthen the international norms against these means and methods of war.

It will bolster the Convention on Cluster Munitions, increasing its influence among countries that have not already joined; encourage the adoption a robust political declaration on explosive weapons in populated areas; and in so doing, help improve protections for civilians in future conflicts.