Cluster bombs (also known as Cluster munitions) are a type of weapons that open in mid-air and disperse smaller submunitions— anywhere from a few dozen to hundreds—into an area. It can be explosive, chemical or biological in nature. They can be delivered by aircraft or from ground systems such as artillery, rockets, and missiles.
Commonly, cluster bomb that ejects explosive bomblets are designed to kill personnel and destroy vehicles. Other cluster munitions are designed to destroy runways or electric power transmission lines, disperse chemical or biological weapons, or to scatter land mines. Some submunition-based weapons can disperse non-munitions, such as leaflets.
Cluster munitions are valued militarily because one munition can kill or destroy many targets within its impact area, and fewer weapons systems are needed to deliver fewer munitions to attack multiple targets. Cluster munitions also permit a smaller force to engage a larger adversary and are considered by some an “economy of force” weapon.
However, Cluster bombs pose a high risk to civilian as its effects is spread over a wide area. Even if military targets are bombed with precision, civilian infrastructure nearby will also be hit. Unexploded bomblets can kill or maim civilians even after a conflict has ended.
Cluster bombs were first used in World War II, and inclusive of their debut, cluster munitions have been used in at least 21 states by at least 13 different countries. The traditional cluster bomb is still in widespread use with thousands of the munitions being used since the invasion of Iraq began in 2003. They continue to be a favorite among those tasked with destruction of enemy air defenses (DEAD) along with battlefield interdiction against formations of vehicles and troops. Even some close air support missions, especially those where the exact target’s location is unknown, benefit heavily from cluster munitions.
On 21 February, the Egyptian military released a video on its official twitter account of what it claimed were improvised explosive devices planted by “terrorist elements”. However, Amnesty International has analysed this video and confirmed it shows an unexploded US made Mk 118 cluster munition, which could only have been dropped by the Egyptian air force.
Russian armed forces have used at least six types of cluster munitions in attacks in Ukraine, and Ukrainian forces also appear to have used them at least once. Russian forces have repeatedly used cluster munitions in attacks that killed hundreds of civilians and damaged homes, hospitals and schools since its invasion of Ukraine.
In Mykolaiv, for example, Russian forces launched cluster munition rockets into populated areas on March 7, 11 and 13, killing civilians and damaging homes, businesses and civilian vehicles. One of the March 13 attacks killed nine people who were waiting in line at a cash machine, local media reported. Russia has not denied using cluster munitions. It alleged that Ukrainian forces used cluster munitions in the city of Donetsk on March 14, but this has not been independently confirmed.
The New York Times reported that Ukrainian forces apparently used Uragan cluster munition rockets in an attack on Husarivka in Kharkiv oblast on March 6 or 7, when the village was under Russian control. Ukraine has not denied using cluster munitions in the current conflict but said that “the Armed Forces of Ukraine strictly adhere to the norms of international humanitarian law.”
The cluster munitions currently used in Ukraine are launched from the ground in rockets and missiles with the exception of the RBK-series cluster bomb, which is delivered by aircraft. The cluster munitions were all manufactured in Russia, some as recently as 2021, or in its predecessor state, the Soviet Union.
“Russian forces’ repeated use of cluster munitions in populated neighborhoods in Ukraine causes immediate and long-term civilian harm and suffering and needs to stop,” said Mary Wareham, arms advocacy director at Human Rights Watch and author of the report. “Ukraine should also stop using these brutal weapons before more civilians are harmed.”
A basic cluster bomb consists of a hollow shell and then two to more than 2,000 submunitions or bomblets contained within it. Some types are dispensers that are designed to be retained by the aircraft after releasing their munitions. The submunitions themselves may be fitted with small parachute retarders or streamers to slow their descent (allowing the aircraft to escape the blast area in low-altitude attacks).
Two technical characteristics of submunitions—failure rate and lack of a self-destruct capability—have received a great deal of attention. There appear to be significant discrepancies among failure rate estimates. Some manufacturers claim a submunition failure rate of 2% to 5%, whereas mine clearance specialists have frequently reported failure rates of 10% to 30%. %.
A number of factors influence submunition reliability. These include delivery technique, age of the submunition, air temperature, landing in soft or muddy ground, getting caught in trees and vegetation, and submunitions being damaged after dispersal, or landing in such a manner that their impact fuzes fail to initiate.
Civilian Harm and policy
Because cluster bombs release many small bomblets over a wide area, they pose risks to civilians both during attacks and afterwards. Unexploded bomblets can kill or maim civilians and/or unintended targets long after a conflict has ended, and are costly to locate and remove. Cluster munitions have been highly criticized internationally for causing a significant number of civilian deaths, and efforts have been undertaken to ban and regulate their use.
Submunitions lacking a self-destruct capability—referred to as “dumb” munitions—are of particular concern because they can remain a hazard for decades, thereby increasing the potential for civilian casualties. Some nations are developing “smart” or sensor-fuzed weapons with greater reliability and a variety of self-destruct mechanisms intended to address the residual hazard of submunitions. Amnesty International arms experts’ analysis of the Mk 118 cluster submunition shown in the video reveals that it is untampered with and in good condition despite its age, with the serial number still clearly visible on its side. This suggests that the submunition has been deployed in recent operations
Cluster munitions are prohibited for those nations that ratify the Convention on Cluster Munitions, adopted in Dublin, Ireland in May 2008. The Convention entered into force and became binding international law upon ratifying states on 1 August 2010, six months after being ratified by 30 states. As of 1 April 2018, a total of 120 states have joined the Convention, as 103 States parties and 17 Signatories.
The 2008 policy required that the US not use cluster munitions that result in more than 1 percent unexploded ordnance (UXO) from 2019 onward. The new policy allows US military commanders to approve use of existing cluster munitions “until sufficient quantities” of “enhanced and more reliable” versions are developed and fielded. The new policy also facilitates US acquisition of cluster munitions from foreign sources to replenish stocks.
However, United States’ recently ended its longstanding policy not to use unreliable cluster munitions and to destroy its stocks completely disregards the widely accepted international ban on these weapons, said Human Rights Watch. A Department of Defense policy memo signed on November 30, 2017, by Deputy Defense Secretary Patrick Shanahan indefinitely delays implementation of a ban on using unreliable types of cluster munitions that was due to take effect on January 1, 2019. For some nations, replacing “dumb” and high-failure rate cluster munitions may not be an option—China, Russia, and the Republic of Korea maintain that they cannot afford to replace all current submunitions with “smart” submunitions.
Development of Newer safer accurate Cluster Bombs
The Pentagon is on one hand trying to improve the safety, accuracy and reliability of cluster munitions as well as finding new ways to achieve the same affects smartly. U.S. mainly uses guided cluster bombs in the form of the Wind Corrected Munitions Dispenser (WCMD). This is basically a guided tail-kit attached to existing cluster bombs that uses an internal inertial guidance system to fly towards its target area.
It does not make these cluster bombs precision-guided munitions but increases their accuracy by compensating for wind encountered during the canisters’ fall. The WCMD can reduce humanitarian harm by making it less likely civilians will be hit by a cluster bomb that goes astray (a significant problem in Afghanistan where the older CBU-87 was used widely). It does not make cluster bombs precision munitions that are safe to use in populated areas, nor does it eliminate the duds that endanger civilians after strikes.
Many cluster munitions rely on simple mechanical fuzes that arm the submunition based on its rate of spin and explode on impact or after a time delay. A newer generation of sensor-fuzed submunitions is being introduced by a number of nations to improve the munitions’ and submunitions’ accuracy and to reduce the large number of residual unexploded submunitions. These sensor-fuzed submunitions are designed to sense and destroy vehicles without creating an extensive hazard area of unexploded submunitions.
The SFW has the same canister as the more common CBU-87 or -103, but it contains ten BLU-108 submunitions instead of 202 BLU-97s. The SFW’s submunitions each contain four hockey puck-sized, explosive “skeets” with infrared sensors that guide them to armored targets and self-destruct mechanisms to reduce the number of duds. They have the potential to reduce the civilian cost of cluster munitions because both their canisters and skeets are guided and because their dud rate should be lower. They also target vehicles and do not create an indiscriminate antipersonnel effect.
Another idea is to replace cluster bomb’s grenade-like sub munitions with non-explosive kinetic projectiles. Thus high-speed hot cast iron shrapnel are used to tear apart the enemy and their armor and once the bomb is detonated, its cast iron, pieces fall to the earth and stay there harmlessly rather than like time bombs waiting to be blasted. The degradation of wide area effect destruction effect of a dispenser concept like the popular CBU-87 Combined Effects Munition currently in service, can be partly compensated with improvements in bomb guidance.
Development of Lethal Cluster munitions
U.S. Army has been working on a Cluster UAS Smart Munition for Missile Deployment which looks like a real-world embodiment of AFADS. The Cluster Swarm project is developing a missile warhead to dispense a swarm of small drones that fan out to locate and destroy vehicles with explosively formed penetrators or EFPs. (An EFP spits a high-speed slug of armor-piercing metal some tens or hundreds of meters). This is similar in concept to the existing CBU-105 bomb, a 1000-pound munition which scatters forty ‘Skeet’ submunitions each over the target area, each of which parachutes down, scanning the ground with a seeker until it finds a tank and fires an EFP at it; the picture above shows one test. CBU-105’s dropped by B-52 bombers successfully knocked out entire Iraqi tank columns in 2003, leading them to be termed ‘Cans of whup-ass.’ The Cluster Swarm would be vastly more powerful.
The Cluster Swarm involved drones packed into the Army’s existing GMLRS rockets, which carry a 180-pound payload and have a range of over 70 kilometers, or ATACMS missiles that carry a 350-pound payload over 270 kilometers. The original idea was that the missile payload would be quadcopter drones encased in an aerodynamic shell that would disperse them over the target area. However, the challenges of unfolding quadcopters mid-air may have been too great, as the Phase II development, recently completed, went to AVID LLC, who have a slightly different approach.
The Cluster Swarm would be far more powerful than the existing CBU-105 ‘cans of whup-ass’ for two reasons. A CBU-105 can only hit targets in an area a few hundred meters across. The Cluster Swarm can go hunting for vehicles dispersed over many square miles. The other advantage is efficiency. CBU-105 gives little overlap in search area for each warhead; many will not have a target, and where there is overlap two or more may attack the same tank and ignore others. A true swarm acting co-operatively will ‘de-conflict’ so forty drones always attack forty different targets.
The Phase II development completed in March included “deployment…powered flight, acquisition of a representative target, and automated navigation to and landing on target” as well as a separate demonstration of the EFP warhead’s effectiveness. If the Army go ahead with Phase III and integrate the drones into a missile warhead, deployment could follow soon.
If Cluster Swarm drones have EFP warheads similar to existing weapons, then each MLRS missile would release about ten drones. Each M270 MLRS vehicle fires twelve missiles in a salvo, for a hundred and twenty drones. So a battery of nine launch vehicles would deliver a thousand killer drones over the target area, enough in theory to stop an entire armored division in its tracks.
The U.S. is not the only player in this field, and may not even be the leader. Turkey has already fielded Kargu tactical kamikaze drones in small numbers on the Syrian border. Currently these are piloted remotely, but the makers claim the Kargu has autonomous swarming capability. China and Russia are not so far behind.
In Sep 2020, China conducted a test involving a swarm of loitering munitions, also often referred to as suicide drones, deployed from a box-like array of tubular launchers on a light tactical vehicle and from helicopters. This underscores how the drone swarm threat, broadly, is becoming ever-more real and will present increasingly serious challenges for military forces around the world in future conflicts. The China Academy of Electronics and Information Technology (CAEIT) reportedly carried out the test in September.
Kallenborn, an expert in unmanned systems and WMD, describes one type of swarm that he calls an Armed, Fully-Autonomous Drone Swarm, or AFADS. Once unleashed an AFADS will locate, identify, and attack targets without human intervention. Kallenborn argues that an AFADS-type swarm is a genuine Weapon of Mass Destruction because of the amount of harm it can do and because of its inability to distinguish civilians from military targets.
“However, it would depend on the number and payload of armed UAVs [Unmanned Aerial Vehicles] within the swarm.” Kallenborn says that as a rough rule of thumb, a swarm with munitions equivalent to a thousand M67 hand grenades would likely be in the WMD class. If it meets this threshold, then according to his new paper the swarm could be subject to international arms control law.