Cluster Bombs and Cluster Submunitions: Why a Widely Banned Weapon Still Shapes Modern War

Cluster bombs are back in the headlines because the weapon never really disappeared. It stayed in arsenals, in contaminated fields, and in the law books of states that never joined the global ban. Now, as the treaty system heads toward a major 2026 review conference, the issue is moving in two directions at once: Vanuatu became the 112th state party on March 1, 2026, while Lithuania’s withdrawal took effect on March 6, 2025, marking the convention’s first loss of a member. That contrast captures the story of cluster munitions today: expanding stigma on one side, renewed military interest on the other.

At the technical level, a cluster bomb is only one type of cluster munition. The broader term covers weapons launched from the air or the ground that open and disperse many smaller explosive submunitions over a wide area. Under the Convention on Cluster Munitions, a cluster munition is a conventional munition designed to disperse or release explosive submunitions weighing less than 20 kilograms. Those submunitions are the real hazard. They are the bomblets that fall across streets, farms, school grounds, and roofs, and they are often what civilians later encounter as unexploded ordnance.

That definition matters because the public conversation often blurs three different things: the carrier, the payload, and the remnants. The carrier may be an aircraft bomb, artillery shell, rocket, or missile. The payload is the set of explosive submunitions inside. The remnant is what stays behind when some of those submunitions fail to explode on impact. The treaty also excludes certain weapons from the ban if they are designed to avoid indiscriminate area effects and meet strict technical conditions, including fewer than ten submunitions, each weighing more than four kilograms, target-detection capability, and electronic self-destruction and self-deactivation features.

Militaries have historically valued cluster munitions because they can strike multiple dispersed targets in one salvo. In Cold War planning, that meant formations of armor or infantry spread over a broad area. Humanitarian objections focus on exactly the same feature. A weapon designed to cover a large footprint is difficult to confine in populated areas, and when submunitions fail to detonate, the attack continues long after the aircraft or artillery battery is gone. The ICRC says cluster munitions scatter huge numbers of explosive submunitions across several thousand square metres, often well outside the intended target area, and leave contamination that endures in neighborhoods, forests, and farmland.

That is why the civilian toll remains central to every serious discussion of cluster bombs. For calendar year 2024, the latest global monitoring recorded 314 cluster munition casualties across nine countries. Of those, 257 were caused by attacks and 57 by remnants. All recorded casualties in 2024 were civilians. The dataset almost certainly understates the true toll, especially in active war zones where access is restricted and many incidents go unverified. Even so, the pattern is consistent: cluster munitions and their remnants keep showing up in civilian casualty records because they are used in or near places where ordinary life continues.

The longer historical picture is even starker. Through the end of 2024, monitors had recorded 24,816 people killed or injured by cluster munitions worldwide, including 6,024 casualties from direct attacks and 18,791 from unexploded remnants. Because many older incidents were never formally documented, the same monitoring project estimates that at least 56,800 casualties have occurred worldwide. The countries with the highest recorded totals include Lao PDR, Syria, Iraq, Vietnam, and Ukraine. Children are especially exposed after fighting ends; in 2024 they accounted for 42% of all recorded casualties from cluster munition remnants.

The contamination map explains why the danger lasts. As of the end of 2024, 29 countries and other areas were contaminated or suspected to be contaminated by cluster munition remnants. Ten of those were states parties to the treaty, and Myanmar was newly added to the list in 2024. Clearance work continues, but it is slow, expensive, and dangerous. In 2024, states parties released 101.85 square kilometres of hazardous land and destroyed at least 83,452 remnants, the highest number of remnants destroyed in five years. Even so, no state party completed clearance in 2024, and five states parties sought deadline extensions in the first half of 2025.

Ukraine remains the main live test case for the weapon’s modern relevance and its modern harm. Monitoring for 2024 and the first half of 2025 found continued use by both Russian and Ukrainian forces, though independent attribution is not always possible for every strike because of limited access to active battle areas. The same monitoring says that at least 15 types of cluster munitions and three types of individual submunitions had been used in Ukraine since February 2022. Through the end of 2024, the global casualty dataset recorded 1,231 cluster munition casualties in Ukraine, making it one of the deadliest contemporary theaters for this weapon.

UN human rights monitors have also tied specific 2025 attacks to cluster munition effects. In a report covering December 2024 through May 2025, OHCHR said the use of cluster munitions in populated areas is incompatible with international humanitarian law because of their inherently indiscriminate nature. The report verified that two ballistic missiles struck central Sumy on April 13, 2025, with the second detonation scattering fragments across a wide area and killing at least 31 civilians while injuring 105 more. OHCHR also documented a March 7, 2025, attack on Dobropillia in which a multiple-launch rocket system likely deployed cluster munitions that caused a significant share of the civilian casualties.

Ukraine is not the only current front. The 2025 monitoring report recorded new use in Myanmar and Syria as well. For Myanmar, the report cites photographs of cluster munition remnants after an airstrike in Rakhine State in January 2024 and recalls a March 2024 UN report stating that the Myanmar military’s use of cluster munitions in civilian-inhabited areas likely constitutes a war crime. Myanmar rejected that characterization, arguing that the munitions it used did not fit the treaty definition. The dispute itself shows how contested classification can become once the evidence is mixed with battlefield propaganda.

Syria offers a different lesson: how long a country can remain contaminated by repeated use. The 2025 monitoring report says Syrian government forces used cluster munitions extensively from 2012 to 2020 and continued to use them in 2021–2024, including attacks documented in Idlib and Aleppo governorates in 2024. The report says it found no evidence that Syria’s transitional government had used cluster munitions after the Assad government fell in December 2024, but the contamination from earlier years remains one of the heaviest anywhere. Even when active use stops, the cleanup burden keeps the weapon politically and morally alive.

The legal framework is straightforward on paper. The Convention on Cluster Munitions was adopted in May 2008 and entered into force on August 1, 2010. It prohibits use, production, transfer, and stockpiling. It also requires states parties to destroy stockpiles within eight years, clear contaminated land within 10 years, and assist victims, including affected families and communities. In treaty design, it is a classic humanitarian disarmament instrument: it does not only ban a weapon; it also creates duties to repair part of the damage already done.

The treaty system has delivered measurable results. Since the convention’s adoption, 42 states parties have destroyed all declared stockpiles, eliminating 1.49 million cluster munitions and 179 million submunitions. Eleven states parties have completed clearance of contaminated areas, with Bosnia and Herzegovina the most recent to do so in 2023. These are not symbolic gains. They translate into farmland returned to use, roads reopened, children able to walk to school more safely, and fewer explosive devices sitting in rubble years after a war has formally ended.

But the treaty has never been universal, and that gap now defines the politics of the issue. The convention’s own website says that, as of March 2026, it has 112 states parties and 12 signatories. At the same time, the 2025 monitoring report says 17 countries still produce cluster munitions or reserve the right to do so, including Brazil, China, Egypt, Greece, India, Iran, Israel, North Korea, South Korea, Myanmar, Pakistan, Poland, Romania, Russia, Singapore, Türkiye, and the United States. That list explains why the norm is strong but incomplete: many states accept the stigma, while several militarily significant states still keep the option open.

The biggest recent political controversy has been transfer, not just use. Monitoring found that between July 2023 and October 2024, the United States announced at least seven transfers of cluster munitions to Ukraine, including multiple types of artillery projectiles and ATACMS variants. Some of those weapons transited through Germany, which is a state party to the convention. The report also says more than 22 world leaders expressed concern about the U.S. decision. That episode laid bare the hardest question in humanitarian disarmament: what happens when states that support the norm confront a war they believe cannot be fought effectively without violating its spirit.

A related political shock came from Lithuania. The UN treaty depositary records that Lithuania’s withdrawal took effect on March 6, 2025. The ICRC called it unprecedented and warned that withdrawing from international humanitarian law treaties erodes protections for civilians. The debate around Lithuania reflects a wider security argument emerging on NATO’s eastern flank: some governments now say treaty restraints make less sense when facing an adversary that never joined them. Humanitarian actors answer that the logic cuts the other way; when war risks rise, the need for enforceable limits should become stronger, not weaker.

Still, the convention has not stalled. Vanuatu deposited its accession instrument in September 2025, and the convention’s website says the accession took effect on March 1, 2026, making Vanuatu the 112th state party. The Third Review Conference is scheduled for September 14–18, 2026, in Lao PDR, one of the countries most heavily scarred by earlier cluster munition use. That venue is symbolic. Lao PDR remains a reminder that the political life of a cluster bomb is often short, but the human life of its remnants can stretch across generations.

The distinction between a cluster bomb and a cluster submunition can sound technical, but it has practical consequences. The bomb or shell may disappear in a single blast. The submunitions determine the strike pattern, the casualty pattern, and the cleanup burden. They are why cluster attacks can hit a wider area than intended, and they are why postwar contamination persists. When people hear the phrase “cluster bomb,” they often imagine one detonation. The evidence shows a different reality: one launch can create dozens or hundreds of explosive risks, some immediate and some delayed, across space that civilians still use every day.

That is the core news value of this issue in 2026. Cluster munitions are not only a weapon story. They are a civilian protection story, a reconstruction story, and a treaty durability story. The law against them has grown, and the humanitarian case against them is stronger than ever. Yet recent battlefield use in Ukraine, Myanmar, and Syria, continued production by non-parties, and the first treaty withdrawal show that the stigma is under pressure. The question for governments now is not whether the weapon is controversial. The evidence settled that years ago. The question is whether states will defend the norm when war makes doing so hardest.

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