How Do Cluster Bombs Work? What Makes Them So Lethal

They fall from the sky like any other bomb—but what happens next is far from ordinary. Instead of a single blast, the explosion seems to multiply, scattering destruction over a wide area. The impact is terrifying, and the danger often doesn’t end when the fighting stops.

First developed during World War II, cluster bombs have been used in conflicts around the globe—from Southeast Asia to the Middle East. Over time, they’ve evolved into more advanced and varied forms, but the core concept remains the same: “deliver maximum damage over a wide zone”.

Today, they’re back in the headlines, especially with reports of their use in the ongoing conflict in Ukraine, reigniting debates about their legality and devastating effects.

So, how do cluster bombs work, and why do they continue to spark global outrage decades after they were first used?

What Are Cluster Bombs?

Definition and Components

At their core, cluster bombs—also known as cluster munitions—are a type of explosive device designed to cover a wide area with multiple smaller explosives. Instead of detonating in one centralized explosion, the main bomb—also called carrier—opens mid-air, releasing dozens or even hundreds of submunitions, commonly referred to as bomblets or grenades. These submunitions are designed to explode on impact, creating a scattered field of destruction that can target both equipment and personnel.

Each bomblet is typically small, sometimes the size of a soda can or tennis ball, but collectively they can cause massive damage. Some are engineered to explode immediately, while others may lie dormant, effectively turning into hidden landmines that pose risks long after the fighting ends. This delayed cluster bomb detonation is one of the reasons these weapons are so controversial in modern warfare.

Types of Cluster Munitions

Cluster bombs can be delivered using various systems, depending on military strategy and the intended target area. Here are the types of cluster bomb delivery methods commonly used:

• Air-dropped cluster bombs, which are released from aircraft. Once the bomb is in the air, it opens up at a certain altitude, dispersing submunitions—also known as bomblets—over a wide radius. These are particularly effective when targeting large formations or spreading damage across enemy lines.
• Artillery-fired cluster munitions. These are launched from ground-based weapons like howitzers or rocket artillery systems. Though similar in function to air-dropped versions, artillery-based cluster bombs are valued for their range and can be used to strike deep into enemy territory without relying on air support.
• Cluster munitions can also be delivered through rocket systems. These rockets are equipped with cluster warheads that release bomblets over the target zone upon reaching a pre-programmed altitude. In more advanced designs, some submunitions may include mechanisms like parachute-retarded submunitions. These tiny parachutes slow the descent of bomblets, helping them spread more uniformly and increasing their effectiveness against dispersed targets.

Depending on the mission, the type of submunitions used will vary:

• Anti-personnel bomblets are intended to harm or kill enemy soldiers. Anti-personnel bomblets explode in a way that releases shrapnel, injuring or killing enemy troops within a certain radius. These are designed to maximize damage to unprotected individuals and disrupt infantry movements.
  
• Anti-armor bomblets, on the other hand, are built to penetrate and destroy vehicles, tanks, and other fortified equipment. They often contain shaped charges that focus the explosive force into a narrow, armor-piercing jet.

How Do Cluster Bombs Work?

Deployment Mechanism

To understand how cluster bombs work, we first need to look at how they are deployed in combat. Cluster munitions are not like traditional bombs that explode in one place. Instead, they are designed to cover a wide area with multiple small explosives called submunitions or bomblets.

The deployment process begins when a military cluster bomb is launched—either dropped from an aircraft (air-dropped cluster bombs) or fired from ground-based systems such as cannons or rockets (artillery-fired cluster munitions). Once the bomb reaches a certain altitude or distance from the target, a time-delayed fuse or an altimeter-based sensor triggers the cluster bomb detonation sequence.

At this point, the bomb’s casing opens mid-air, and dozens or even hundreds of submunitions are ejected. These bomblets are often dispersed using small explosive charges or by spinning the bomb’s outer shell, creating centrifugal force.

In some modern systems, the submunitions are equipped with tiny parachutes—called parachute-retarded submunitions—that slow their fall. This helps to spread them more evenly over a large area, increasing the chances of hitting dispersed targets.

The wide-area scattering of these explosive devices makes cluster bombs particularly effective against groups of soldiers, vehicle columns, or air defense installations. However, the broad coverage also increases the risk of affecting unintended targets, especially in densely populated areas. 

Detonation and Impact

Once the submunitions are released and descend onto the target area, they are designed to explode either on impact or after a short delay, depending on their fuse mechanisms. Many bomblets are impact-triggered—detonating when they hit the ground or a hard surface.

Others are equipped with programmable timers that allow for delayed explosions, adding an element of unpredictability that can deter enemy forces from entering the area immediately after the strike.

In technical terms, the cluster bomb mechanics rely on small internal fuses that react to physical pressure or pre-set timing. Upon detonation, the bomblets release a powerful blast, often accompanied by fragmentation.

The explosion not only damages what it directly hits but also sends out high-speed shrapnel that can injure or destroy nearby targets. In certain models, explosive devices are designed to detonate slightly above the ground (airburst), which increases the range of damage by dispersing fragments in all directions.

The effects of cluster bombs in combat can be devastating. A single cluster bomb can impact an area the size of several football fields, making it highly effective for disabling broad enemy formations, disrupting supply lines, or neutralizing defenses. From a strategic standpoint, these weapons are valued for their ability to exert control over large zones quickly, especially in high-intensity conflicts.

However, not all submunitions function as intended. A percentage of them may fail to explode due to soft ground, technical malfunction, or damage during deployment. These unexploded bomblets remain highly dangerous long after combat ends, acting like hidden landmines.

Technological Developments

Over the years, advancements in military technology have led to the development of more precise and safer versions of cluster munitions. These innovations are largely a response to the growing global criticism surrounding traditional cluster bombs, particularly their high failure rates and the long-term danger posed by unexploded submunitions. To address these issues, modern cluster munitions increasingly incorporate smart submunitions and self-destruct mechanisms.

Smart submunitions are designed to increase accuracy and reduce the chances of failure. Unlike traditional bomblets that simply fall where they are released, smart submunitions can detect and home in on specific targets.

Read also: How Does a Smart Bomb Work

For example, some anti-armor variants can identify the heat signature or shape of a vehicle before detonation. These bomblets are equipped with onboard sensors, target-recognition systems, and more sophisticated cluster bomb mechanics to ensure that they hit only intended targets—minimizing collateral damage and increasing battlefield effectiveness.

Another major innovation is the inclusion of self-destruct mechanisms. These are safety features built into the bomblets to automatically destroy them if they fail to detonate on impact. Typically, the self-destruct is activated after a preset time—often a few minutes or hours—rendering the explosive devices inert if they haven’t already exploded.

In some designs, there’s even a backup self-deactivation mechanism, which disables the fuse or electrical system if self-destruction fails. These systems significantly reduce the number of unexploded submunitions left behind, which has been one of the most controversial aspects of cluster bomb deployment.

For instance, the U.S. military has developed and fielded advanced military cluster bombs like the CBU-105 Sensor Fuzed Weapon. This system uses smart submunitions with sensor-guided target selection and built-in self-destruct features. Each submunition in the CBU-105 can scan for targets using infrared and laser sensors, deploy at the optimal altitude, and self-destruct if no target is found.

While these advancements don’t completely eliminate the risks associated with cluster munitions in warfare, they represent a meaningful step toward reducing harm to civilians and making these weapons more accountable under international humanitarian law.

However, many critics argue that even with such technologies, the cluster bomb controversy continues due to the inherent risks of wide-area damage and the possibility of malfunction.

Historical Use of Cluster Bombs

The use of cluster bombs in warfare dates back several decades, with a history marked by both strategic effectiveness and devastating humanitarian consequences. Their wide-area impact, combined with high failure rates of submunitions, has fueled a global debate over their continued use.

Vietnam War

One of the earliest and most notorious uses of cluster munitions in warfare occurred during the Vietnam War. Between the 1960s and 1970s, the United States conducted extensive bombing campaigns over Vietnam, Laos, and Cambodia. It’s estimated that over 270 million submunitions were dropped on Laos alone, many of which were air-dropped cluster bombs targeting suspected enemy strongholds and supply routes.

However, due to the rough terrain and poor detonation reliability, a significant percentage of these explosive devices failed to go off, resulting in a humanitarian crisis that persists to this day. Decades later, unexploded anti-personnel bomblets continue to maim and kill civilians, especially children who mistake them for toys.

The cluster bomb effects from this era have severely impacted agricultural development, infrastructure, and civilian safety across affected regions, highlighting the long-term consequences of such weapons.

Middle East Conflicts: Lebanon, Iraq, and Syria

The Middle East has been another major theater for cluster bomb deployment. In the 1982 Lebanon War and again during the 2006 conflict, Israel used large quantities of cluster munitions, particularly in southern Lebanon.

Reports suggest that millions of submunitions were dispersed across civilian areas, many of which did not detonate on impact. These remnants continue to pose threats to local populations, farming activities, and post-war reconstruction efforts.

In Iraq, both during the Gulf War (1991) and the Iraq War (2003), U.S.-led coalitions used military cluster bombs against enemy formations and infrastructure. These weapons were deployed through both aircraft and artillery, including artillery-fired cluster munitions.

Similarly, in Syria’s civil war, various factions—particularly the Syrian government—used cluster bombs in densely populated areas, often without regard for civilian safety. The widespread use of anti-personnel and anti-armor bomblets in urban settings has drawn widespread international condemnation and has added to the ongoing cluster bomb controversy.

Recent Deployments: Ukraine and Modern Conflicts

In recent years, cluster bombs have returned to global headlines due to their use in the ongoing conflict between Russia and Ukraine. Both sides have reportedly employed cluster munitions in various offensives, despite growing international pressure to restrict or ban them. The use of delivery methods of cluster bombs, including rocket artillery and aircraft, has raised serious concerns, especially when used in civilian areas.

For example, Russian forces launched a 9M55K-series Smerch rocket equipped with 72 9N235 fragmentation submunitions into a residential area of Lyman on July 8, 2023. The attack targeted a local market where civilians were trading produce, resulting in 9 civilian deaths and at least 13 injuries. Human Rights Watch and France condemned the strike as a potential war crime due to the indiscriminate nature of the weapon used in a populated area.

More recently, on April 14, 2025, a devastating Russian missile strike hit the Ukrainian border city of Sumy, killing at least 34 civilians, including two children, and injuring 117 others. The missiles, believed to have been armed with cluster munitions, were launched from Russia’s Kursk and Voronezh regions. This attack marked the deadliest assault on civilians in Ukraine in 2025. 

Other modern conflicts, such as those in Yemen and Libya, have also seen sporadic use of cluster munitions, often supplied by foreign powers. These incidents have fueled calls from humanitarian organizations for stronger enforcement of international treaties and bans related to cluster bomb deployment.

Conclusion

So, when we ask how cluster bombs work, the short answer is: they’re powerful, wide-area weapons designed to break up into lots of smaller submunitions that spread out and detonate over a target. These explosive devices can be launched from the air using air-dropped cluster bombs, or from the ground with artillery-fired cluster munitions. Some are meant to hit people (anti-personnel bomblets), others go after tanks and vehicles (anti-armor bomblets).

But not all of those little bomblets actually explode when they’re supposed to. That’s where the real problem lies. Unexploded submunitions hang around like deadly traps, often long after the war is over, causing tragic injuries or deaths to civilians. This is what makes cluster munitions so controversial and why many countries have banned them outright.

To reduce that danger, newer tech like smart submunitions and self-destruct mechanisms has been developed. These aim to make cluster bomb detonation more reliable and reduce the number of leftover duds. Still, as we’ve seen in places like Ukraine, Syria, and Lebanon, the humanitarian risks remain huge.

So yes, military cluster bombs might be effective in the heat of battle, but they leave behind a legacy that’s far harder to clean up — and that’s why they continue to be such a hot-button issue in international debates. In the end, understanding cluster bomb mechanics is about asking whether their impact is worth the cost, especially when the battlefield is long gone, but the danger isn’t.