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Cluster Bombs

US Air Dispensed Submunitions

Weapon Submunition Submunition
CBU-7/A BLU-18 1200
CBU-12/A BLU-17/B 213
CBU-24/B BLU-26/B 670
CBU-25/A BLU-24/B 132
CBU-29/B BLU-36/B 670
CBU-46/A BLU-66/B 444
CBU-49/B BLU-59/B 670
CBU-52/B BLU-61A/B 217
CBU-55/B BLU-73/B 3
CBU-58/B BLU-63/B 650
CBU-59/B BLU-77/B 717
CBU-60/A BLU-24/B 264
CBU-63/B M40 2025
CBU-70/B BLU-85/B 79
CBU-71/B BLU-86/B 650
CBU-72/B BLU-73A/B 3
CBU-75/B BLU-63/B 1800
CBU-75A/B BLU-63 1420
BLU-86 355
CBU-76/B BLU-61A/B 290
CBU-77/B BLU-63/B 790
CBU-78/B BLU-91/B 45
BLU-92/B 15
CBU-81/A BLU-49A/B 45
CBU-87/B BLU-97/B 202
CBU-89/B BLU-91/B 92
CBU-89/B BLU-92/B 92
CBU-97 BLU-108/B 10
CBU-98 HB-876LE 24
MK15 M40 2020
MK20 MK118 247
MK22 M38 2020
Mk 118
Clustered bombs have been used extensively in trying to increase the effectiveness of air dropped munitions. These have been used since prior to World War II and basically involved the combination of a number of smaller bombs held together by some frangible or breakable link. These could be dropped together and would separate at the time of drop or during the descent so that they would have separated in distance from each other in the air and retain the capability, individually to damage or destroy the targets which they hit or which were in their area.

In time, it became apparent that it would be more advantageous to further reduce the size of these smaller bombs since computations, dating back to Leonardo DaVinci showed that anti-personnel effectiveness could be greatly improved by accomplishing this. Studies after World War II had shown that relatively small bombs, considerably smaller than those used in clustered bombs, could destroy tanks, armored vehicles, trucks and similar military vehicles. It soon became apparent that it was difficult and costly to place such larger numbers of much smaller bombs in clusters and reliably and safely hold them together for aircraft drop. This led to the placement of such clustered smaller bombs within the confines of a larger bomb, acting as a container for the smaller bombs, where, after drop from the aircraft, the bomb would open and somehow disperse the cargo of the contained smaller bombs over a target area.

The initial and continuing problem in trying to accomplish the ejection and dispersion of the cargo of such larger bombs has been the means of accomplishing this objective. Actually, two types of clustered dispensing systems came into being. One is commonly known in the U.S. as Slung Under Unit Dispensers or SUU Dispensers. These are hung under aircraft and directly used to dispense a cargo of munitions, through RAM air or propellants with the dispenser container retained on the aircraft. The United States Air Force has been using such SUU dispensers extensively. Here smaller bombs or other munitions are dispensed usually out of the rear end of SUU dispensers as a result of forces applied against the cargo to cause it to eject rearward. Thus Ram air was used frequently to eject the cargo of munitions.

The United States Navy was of the opinion that the aircraft dispensing of munitions, requiring a flight over the target would result in excessive losses to enemy air defenses. The Navy consequently developed an alternate form of dispensing clustered munitions, which would not require a flight over the target. Instead of leaving the dispenser on the aircraft during the dispensing of the munition, the dispenser itself was dropped from the aircraft and designed in a missile configuration, so as to fly toward the target, while the aircraft would turn so as to permit the aircraft to be out of gun reach of the defending gun positions. In one tactical use, this dispenser, which is now known as a cluster bomb, would be dropped from great altitudes at long distances from the target where the aircraft was out of reach of most air defense weapons. The forward velocity of the aircraft would to a large extent be retained by the aerodynamically shaped cluster bomb and would permit it to fly a long distance in the direction of the target before the cargo of munitions would be dispensed from that bomb to cover all or part of the target area.

In a second tactical use the aircraft would be flying at a low altitude. As it approached the target area, it would fly upward and release the cluster bomb on the "up-leg" of flight. This upward angle of flight of the cluster bomb would cause it to fly in a mortar shaped flight configuration. The cluster bomb, which is in effect a missile would fly a considerable distance toward the target area, to discharge the cargo of submunitions over the target area. The aircraft would turn and not be required to fly over the target area.

A major problem in the design of a cluster bomb as described above involved the complexity and resulting cost, as well the safety of such bombs. A cluster bomb had to be fuzed such that the dispensing of smaller bombs, mines or grenades could be conducted efficiently and reliably. Consequently, various designs of the cluster bomb were produced to properly contain and be able to discharge the cargo of munitions. These designs used a number of basic techniques, including combinations of such techniques to eject and disperse the cargo of munitions. This required the packing of the munitions such that they could be dispersed from the cluster bomb without damage. It further was a desire to pack the maximum cargo of munitions within the cluster bomb.

There has been a continuous desire to produce lower cost, easier to fabricate and safer to handle cluster bombs. Normally, the container main body of cluster bombs are fabricated from metal or plastic components and, therefore, cluster bombs can be manufactured competitively in a very large number of industrial organizations. Competition drives the cost down to a minimal amount. But, once energetic materials, such as propellants, explosives or pyrotective materials must be attached to that body or container, then the competition is effectively eliminated since only one or two special facilities in the locality can handle such energetic materials. Governmental restrictions severely limit the licenses given out to organizations authorized to handle explosives, propellants or pyrotechnic materials. These organizations need extra land and special facilities to store these energetic materials. Operators need special training and receive higher pay. Storage, handling and transportation requirements are severe and increase costs. There is always the potential of accidents with explosives, propellants or pyrotechnic materials. This forces special handling of loaded items. Even cluster bomb bodies containing small amounts of explosives require special handling and escort of police or similar protection during transportation, especially across bridges and through tunnels. All of these considerations cause a higher cost for energetically loaded cluster bomb bodies as compared to inert bodies which do not contain explosives or propellants.

Saturation of unexploded submunitions has become a characteristic of the modern battlefield. The potential for fratricide from unexploded ordnance [UXO] is increasing. Joint Publication 1-02 defines unexploded explosive ordnance as "explosive ordnance which has been primed, fused, or otherwise prepared for action, and which has been fired, dropped, launched, projected, or placed in such a manner as to constitute a hazard to operations, installations, personnel or material and remains unexploded either by malfunction or design or for any other cause." Although ground forces are concerned with all unexploded ordnance, the greatest potential for fratricide comes from unexploded submunitions.

Submunition function reliability requirement is no less than 95 percent. With a 95 percent submunition function reliability, one CBU-58 (with 650 submunitions) could produce up to 38 unexploded submunitions. A typical B-52 dropping a full load of 45 CBU-58/CBU-71, each containing 650 submunitions, could produce an average of some 1700 unexploded sub-munitions. The numbers of submunitions that fail to properly function and the submunitions' dispersion determine the actual density of the hazard area.

After the Kosovo conflict in 1999 much effort has been made to handle the mine and UXO problem in the region. According to the UN Mine Action Co-ordination Center (UNMACC) in Pristina the total number of mines and UXO cleared by 8 March 2001 was assessed at 84,046. More than 55,000 pieces of ammunition had been disposed of, including UXO produced through the failure of munitions to function (duds). The UK EOD unit of the Multi-National Brigade (Centre) carried out investigations of all strike areas in the area of responsibility and prepared statistics for the assessed failure rates. The average failure rates for sub-munition type BLU-97 was assessed at 7.1% and the failure rate for sub-munition type BL755 was assessed at 11.8%.

Studies that show 40 percent of the duds on the ground are hazardous and for each encounter with an unexploded submunition there is a 13 percent probability of detonation. Thus, even though an unexploded submunition is run over, kicked, stepped on, or otherwise disturbed, and did not detonate, it is not safe. Handling the unexploded submunition may eventually result in arming and subsequent detonation.

The Cluster Munitions Policy Memo (19 June 2008) directed that after 2018, cluster munitions must not produce >1% UXO; a limit that will not be waived. It provided no differentiation between types of UXO (hazardous or non-hazardous duds). All cluster munition stocks that exceed operational planning requirements will be removed from the inventory as soon as possible, but not later than June 2009. The previous UXO Requirement: < 2% 20-60km; < 4% < 20km and > 60km. GMLRS DPICM with Self Destruct Fuze (SDF) development and performance demonstrated "hazardous" dud rate of only 0.15%, overall UXO 3.7%, which does not comply with the new DOD Policy.

On 03 December 2008 Representatives from more than 100 governments began signing a document binding their countries not to make, stockpile, or use cluster bombs in a two-day signing ceremony in the Norwegian capital, Oslo. The signatories include the Cook Islands in the Pacific, the Vatican's Holy See, the Republic of San Marino, the Seychelles, and Papua-New Guinea. Many military powers -- namely the United States, Russia, China, Israel, India, and Pakistan -- declined to sign the ban. Arab states are not signing, in response to Israel's action. Anatoly Antonov, the head of the Department for Security and Disarmament of Russia' Foreign Ministry, said that cluster bombs are legal and effective weapons which are allowed by international law. US Department of States spokesman Robert Wood said that the Bush administration considers the bombs essential in modern warfare.

On 28 May 2008 diplomats from more than 100 countries meeting in Ireland agreed on a draft treaty outlawing cluster bombs. The draft would give signatory nations eight years to destroy their cluster bomb stockpiles. British Prime Minister Gordon Brown said his government will stop using cluster bombs. But the United States, one of the world's largest builders of the bombs, opposes a ban. The US, Israel, Russia, China, India and Pakistan were not present at the Dublin meeting. Under pressure from NATO countries, the text of the anti-cluster-bomb convention contained a concession to the US and other countries which want to continue to use and produce such munitions, by allowing military cooperation between signatories and non-signatories. The 2008 Convention on Cluster Munitions, commonly referred to as the Oslo Treaty, has two aims. The first is to reduce unintended harm to civilians by minimizing the indiscriminate effects of area fires (intended to inundate a target area greater than 200 square meters with explosive destruction) on the battlefield. Area fires are more likely to cause collateral damage and civilian casualties. The second is to eliminate the large amount of unexploded sub-munitions, or bomblets, commonly found in areas where cluster munitions have been fired. Up to five percent of bomblets from cluster munitions may not explode when fired, which can wreak havoc on local civilian populations for years.

In 2008, when the US government committed itself to disposing of cluster munitions by January 2019, it seemed distant. Although the United States is not a signatory to the treaty, the Bush Administration supported the spirit of the treaty, as does the Obama Administration. The Bush Administration directed DoD to implement a policy to meet the intent of the treaty but to do so without giving up a key capability for an interim period while the Services determine how to replace the capability.

Elimination of the cluster munition created an important debate within the DoD community regarding the need for a comparable replacement. The debate hinges on a perception of a very low likelihood of future conflicts involving large enemy armor and infantry formations, leading to the elimination of large scale area fire in combat and shifting toward precision unitary fire.

The policy gave the Services a 10-year grace period to determine the requirement for a replacement, conduct research and development, and acquire sufficient new munitions. To date the services, with the exception of the Army, have failed to accomplish any of these activities, despite a clause within the policy that acknowledges the importance of this capability.

The policy states, "[T]here remains a military requirement to engage area targets that include massed formation of enemy forces, individual targets dispersed over a defined area, targets whose precise locations are not known, and time-sensitive or moving targets. Cluster munitions can be the most effective and efficient weapons for engaging these types of targets."

Even the State Department agrees. "Cluster munitions have demonstrated military utility. Their elimination from U.S. stockpiles would put the lives of its soldiers and those of its coalition partners at risk. Moreover, cluster munitions can often result in much less collateral damage than unitary weapons, such as a larger bomb or larger artillery shell would cause, if used for the same mission."

Reliance on precision creates a new capability gap when prosecuting hardened targets that cannot be precisely located (i.e., armored fighting vehicles and tanks). Cluster munitions, with their saturative effects, were designed for exactly this purpose. Furthermore, the effectiveness of engaging concealed, hardened targets is reduced when using unitary munitions. Potential consequences include decreased lethality, increased munitions expenditure, and increased targets requiring engagement with direct fire weapon systems, thus increasing risk to soldiers and marines.

What has been confirmed through the sum of U.S. and international assessments is that technological advancements have greatly reduced the need for cluster munitions and when taken in the context of collateral damage it just makes sense to phase out this capability. However, doing so creates additional operational risk to ground forces that has been mitigated by cluster munitions since the 1970's. Advances in precision technology coupled with development of a new sensor-fuzed artillery munition will not only close the gap but arguably increase the lethal effectiveness of ground force indirect fires against armored and hardened targets.

Regardless of its type or purpose, dropped ordnance is dispensed or dropped from an aircraft. Dropped ordnance is divided into three subgroups: bombs; dispensers, which contain submunitions; and submunitions.

Cluster munitions (CBUs) fall into the dumb bomb or unguided category with the exception of the BLU-108/B Sensor Fuzed Weapon and Wind Corrected Munition Dispenser (WCMD). CBUs combine dispensers, fuzes, and submunitions into a single weapon with a specialized or general purpose mission. Once released, CBUs fall for a specified amount of time or distance before their dispensers open, allowing the submunitions to effectively cover a wide area target. The submunitions are activated by an internal fuze, and can detonate above ground, at impact, or in a delayed mode.


Dispensers may be classified as another type of dropped ordnance. Like bombs, they are carried by aircraft. Their payload, however, is smaller ordnance called submunitions. Dispensers come in a variety of shapes and sizes depending on the payload inside. Some dispensers are reusable, and some are one-time-use items.

Dropped dispensers fall away from the aircraft and are stabilized in flight by fin assemblies. Dropped dispensers may be in one piece or in multiple pieces. All dropped dispensers use either mechanical time or proximity fuzing. These fuzes allow the payload to be dispersed at a predetermined height above the target. Multiple-piece dispensers open up and disperse their payload when the fuze functions. Single-piece dispensers eject their payload out of ports or holes in the body when the fuze functions.

Attached dispensers stay attached to the aircraft and can be reloaded and used again. Their payload is dispersed out the rear or from the bottom of the dispenser.


Most airframes are capable of delivering a variety of submunitions. There is no set air delivery mission profile. The hazard area depends on the submunition, mission profile, target type, and number of sorties. Air Force and naval air power employ cluster bomb units (CBUs) containing submunitions that produce hazard areas similar to MLRS/ cannon artillery submunitions. Air delivered canisters contain varying amounts of CBUs. One CBU-58 or three CBU-87/ CBU-52 contain approximately the same number of submunitions as one MLRS rocket with 644 submunitions. A B-52 dropping a full load of 45 CBUs (each CBU-58/CBU-71 contains 650 submunitions) may produce an hazard area that is significantly more dense than an MLRS hazard area. A typical F-16 flying close air support (CAS) against a point target may drop two CBUs per aircraft per run, thus producing a very low-density hazard area.

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