Cluster Munitions No More: What This Means for the U.S. Military

Slide 1
Figure 1. DPICM M483A1 area effects.
Slide 2
Figure 2. HE point detonation/quick (precision or near-precision).
Slide 3
Figure 3. HE variable time/proximity (near-precision, area).
Slide 4
Figure 4. Matching artillery munitions to targets and conditions.

The end of American cluster munitions is arriving and the Department of Defense (DoD) has no plans to replace them. In 2008, when the U.S. government committed itself to disposing of cluster munitions by January 2019, this milestone seemed distant. Unfortunately, when DoD implements the final phase of this policy, it will deprive itself of a critical capability without a replacement.

What are cluster munitions and why are they so important?

Cluster munitions are “munitions composed of a non-reusable canister or delivery body containing multiple, conventional, explosive sub-munitions” delivered by aircraft, cruise missiles, artillery, mortars, missiles, tanks, rocket launchers and naval cannons. DoD developed cluster munitions during the Cold War to saturate likely Soviet mechanized and armored forces avenues of approach into Western Europe with armor-killing munitions. For example, the typical howitzer-launched cluster munition, the most numerous and, arguably, most important of U.S. cluster munitions, can equal the lethal effectiveness of 15 high-explosive (HE) howitzer shells. The advantages of such a munition are obvious.

The cluster-munition debate

Presently, no replacement has been identified for the vast stockpile of U.S. Army and Marine Corps howitzer munitions that will be eliminated in just a few years. Elimination of the cluster munition created an important debate within the U.S. military 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 artillery fire in combat and shifting toward precision unitary artillery fire.

Advocates of this position point to the experiences of the past 13 years of low-intensity warfare, which did not require U.S. forces to employ cluster munitions. Advocates are further bolstered by the downward pressure on the U.S. defense budget, which does not currently support a replacement capability. Supporters also argue that future state adversaries will not apply combined-arms maneuver against the United States because of our overmatch in technology, particularly when it comes to air superiority.

Unfortunately, these arguments are flawed. Proponents of eliminating the cluster munition dismiss the capabilities of America’s most dangerous adversaries. If DoD does not invest in a replacement capability, it will leave U.S. ground forces at a dangerous disadvantage on future battlefields. Furthermore, by removing a key American deterrent, current and future adversaries may become more aggressive.

Oslo Treaty

The policy to eliminate cluster munitions was America’s buy-in to the Convention on Cluster Munitions signed in Norway in 2008, commonly referred to as the Oslo Treaty. The treaty has two aims: first, 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 aim is to eliminate the large amount of unexploded sub-munitions, or bomblets, commonly found in areas where cluster munitions have been fired. Up to 5 percent of bomblets from cluster munitions may not explode when fired, which can wreak havoc on local civilian populations for years.

In response, the Oslo Treaty prohibits signatories from manufacturing, acquiring, distributing or using cluster munitions. 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.

The DoD policy began to take effect in 2009. All munitions that could not achieve an unexploded ordnance rate of less than 1 percent (which includes all U.S. artillery munitions) were immediately placed under the release authority of the combatant commander. No artillery cluster munitions were fired in Operation Iraqi Freedom following the end of the forced-entry phase of operations (declared by President George W. Bush onboard the USS Abraham Lincoln May 1, 2003) or in Operation Enduring Freedom. The policy gave the services a 10-year grace period to determine the requirement for a replacement, conduct research and development, and acquire enough 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.”

The State Department agrees. A State Department Webpage explains: “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.”1 (italics in the original)

Specifics of cluster munitions

The U.S. Army developed a new warhead for its Guided Multiple Launch Rocket System that will service large, soft-skinned area targets such as encampments, infantry in the open and truck formations. But this munition is allocated to corps and division level and may not always be readily available to tactical formations at brigade, battalion and company level.

For land forces at the tactical level of engagement, the most important system today for prosecuting area targets is the 155mm artillery Dual-Purpose Improved Conventional Munition (DPICM) M483A1 (Figure 1). The projectile is equipped with a time fuze set to release the cargo of sub-munitions at the recommended height above the target (which varies based on the size and density of the target as well as on the number of howitzers available to mass fires on the target) and saturate the area with bomblets. The M483A1 carries 88 bomblets (with a shaped charge for armor penetration), each with a lethal radius of about 10 square meters. The dispersion area is between one to three hectares2 depending on the height of burst. The higher the height of burst, the broader the dispersion. Harder targets require denser dispersion. Shaped charges that strike an armored target create a metallic jet that perforates metallic armor. Some modern medium battle tanks of many advanced states (i.e., North Atlantic Treaty Organization, Russia, China, etc.) can take the hit, but others cannot. Generally, 10 or more bomblet strikes are required for an armored-vehicle kill, but a single bomblet can result in a firepower or mobility kill. Bomblets detonate at surface level. The detonation and most fragmentation travels downward, so most lethal effects are close to the surface.

Cluster-munitions elimination studies

The Army has conducted four studies and the Marine Corps has conducted one study in 2009, 2010, 2012 – and two in 2014 – to determine the operational risk associated with the loss of cluster munitions. Norway conducted a study of its own in 2008 that is arguably the best of all analyses conducted so far. None has been conclusive or definitive. All the studies found that there is some reduction in U.S. artillery kills of enemy forces with the removal of cluster munitions. But they don’t agree how large that reduction would be. Estimates range widely from as high as 25 percent to as low as 4 percent. In the most recent Army assessment, the lethality of Army artillery actually improved when cluster munitions were removed.

What accounts for the erratic results and the inability of the Army and Marine Corps to come to terms with whether or not to invest in a replacement? The answer is a disagreement about the nature of warfare the United States is likely to encounter today and in the future.

All the Army studies have focused on hypothetical regional despots with outdated equipment and doctrine based on Soviet-era technology and principles. The hypothetical enemies lack air parity with the United States. Therefore, all these scenarios assume U.S. air dominance. These studies further assume that these hypothetical enemies have learned the lessons wrought twice on the Iraqi army: namely, the use of Soviet-era armor technology in combined-arms maneuver against the United States military is a really bad idea. Therefore, the Army cluster-munition assessments assume there will not be many “area targets.”

In the most recent assessment, the unclassified report stated: “[B]ased on intelligence analysis, the following guidance was used to model the behavior of current and future threat in the study: with the exception of a slow-moving medium armor threat, no other cluster-munition-designed targets (area targets) are present in the current or projected operational environment within the selected study scenarios.”

Unfortunately, the Army studies contain flaws. None of the Army studies considers the possibility of peer or near-peer competitors. All the studies assume no disruption to friendly-force Global Positioning System (GPS) technology. On a strategic level, all the studies ignore the deterrent effect this capability might have on potential adversaries’ “go-to-war” calculus. Finally, the studies disregard recent technological advances made by potential peer competitors – such as Russia and China – in both cluster munitions and sensor-fuzed weapons (weapons that seek and guide to specific types of targets). Russia and China are not eliminating their inventory of cluster munitions.

Furthermore, none of the Army studies offers any qualitative analysis, such as the use of cluster munitions to prepare areas of the battlefield for assault; shape areas of the battlefield by using cluster munitions for harassment or area denial; and allocate limited artillery assets to support various units during a battle (perhaps leaving others without any artillery support other than their organic howitzers). The studies are based strictly on quantitative analysis derived from modeling and simulation and provide only numerical results, such as reductions in enemy casualties or increases in friendly losses. Qualitative analysis could provide additional important operational considerations such as:

  • The psychological effect on the enemy’s continued will to fight, particularly after witnessing the devastating effects of cluster munitions on adjacent units.
  • The shaping effects of the munition on the enemy’s ability to maneuver or occupy terrain that can influence enemy decisions and actions on the battlefield.
  • Employment of the cluster munition based on unavailability of other fire-support assets due to other fire-support priorities.

Despite these shortcomings, the studies have still validated the U.S. Army’s investment in precision technology over the past 10 years. However, these investments, numbering into the several billions of dollars, are unfortunately heavily reliant on GPS technology and assume the availability of GPS signals against all adversaries. If adversaries are able to somehow render GPS unavailable, the vast majority of precision advantage the U.S. Army enjoys will cease to exist.

That said, those advantages are significant and prolific with considerable secondary benefits, such as reducing the risk of collateral damage and civilian casualties in major combat operations. They are the basis for understanding the argument against pursuing an artillery cluster-munition replacement.

There are three main areas of improvement: the ability of forward observers to determine a precise GPS location of targets; the ability of munitions to guide to a precise grid location; and the ability of indirect-fires platforms to determine a precise grid for their own location. These improvements to artillery technology, together with dominance of the air and enemy reluctance to mass and maneuver against U.S. forces, is what has led to assessments that show minimal impact with the loss of artillery cluster munitions. It is important to note that none of these improvements account for moving targets or large massed targets, both of which are by definition imprecisely located targets.

None of the assessments conducted have included an enemy capable of challenging U.S. air dominance, put GPS availability at risk or field ground-force technology equal to or superior than U.S. ground forces. The Norwegian military assessment of cluster munitions conducted in 2008 did consider peer competitors for obvious reasons. That assessment disclosed that traditional cluster-munition target sets could now be more effectively prosecuted using non-cluster munitions due to improvements in precision and increased effectiveness of unitary HE artillery projectiles. For example, the ability to actually strike a target with the first round fired and the ability to tailor munition effects by using fuze settings that vary detonation to a height of burst, point detonation or delayed detonation significantly improve lethality (Figures 2 and 3).

Capability gap

However, reliance on precision creates a new capability gap when prosecuting hardened targets that cannot be precisely located (i.e., armored fighting vehicles and tanks) (Figure 4). 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.

Mitigating capability gap

Thankfully, there may be a means for closing the gap against imprecisely located hardened and armored targets that does not involve a one-for-one replacement of the stockpile of cluster munitions currently in the inventory. The answer may be sensor-fuzed munitions. This is a family of munitions employed by firing them in an area where enemy vehicles are thought to be located; the munition fuze will then seek out objects on the ground for which its sensors are designed. Having located a target, moving or stationary, the munition then guides to and detonates precisely on the target using its own sensors and without reliance on GPS. The United States fielded such a munition to great effect during Operation Desert Storm in the form of Sense and Destroy Armor (SADARM). However, the munition was not pursued because at the time the large quantities of cluster munitions made the acquisition of this relatively expensive boutique munition unaffordable.

That calculus has changed. The number of SADARM-type munitions that would be required in today’s war reserve would be comparatively small – probably less than 10,000 – because of the relatively small number of targets that would be needed against the low likelihood of a conflict within which such weapons would be employed. This solution would do nothing to mitigate the decreased effectiveness against soft area targets, but with more reliance on corps, division and direct-fire assets, it is safe to assume U.S. ground forces could probably accept the associated risk.


Artillery cluster munitions continue to be a highly effective capability when employed against the right target types under the right conditions. No amount of quantitative analysis against less-than-peer competitors will illustrate the overall risk to U.S. and coalition ground forces when artillery cluster munitions are no longer available. What the sum of U.S. and international assessments has confirmed 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 more operational risk in our ground forces that has been mitigated by cluster munitions since the 1970s. Advances in precision technology, coupled with development of a new sensor-fuzed artillery munition, will not only close the gap but will arguably increase the lethal effectiveness of ground-force indirect fires.

This article is adapted from an article that appeared in War on the Rocks (, a platform for commentary and debate on strategy, defense and foreign affairs. Used with permission.


1; accessed Sept. 10, 2014.

2A hectare is 100 meters by 100 meters.