Why Cluster Munitions Must Be Replaced


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, it seemed distant. When DoD implements the final phase of this policy, it will deprive itself of a critical capability without any plans to fill the giant gap they will leave in the U.S. arsenal. This may seem like a minor issue to many War on the Rocks readers. After all, you might wonder, how important can one class of munitions be? How does this impact strategy? As it turns out, cluster munitions are important to American conventional combat power (as are other capabilities the United States is phasing out) and this issue demands to be reassessed at a higher level. Defense officials should consider a credible and affordable replacement. And this replacement might be found in sensor-fuzed munitions.

The Cluster Munition Debate

Since World War I, artillery has been used to pour large amounts of explosive effects on large areas beyond the direct line of sight or over the horizon. Since artillery effects are often not directly observed and the nature of a ballistic trajectory comes with a large degree of variability, artillery fire has traditionally been employed by using massed cannons firing simultaneously on a large area and destroying everything in that area. As armor became more prevalent in World War II, artillery had to evolve to be able to destroy hard targets that couldn’t be precisely located. Cluster munitions were developed for that purpose. As technology has evolved so has artillery. Targets can now be precisely located using optics tied to GPS and ammunition that can guide itself to specific locations using GPS technology.

Cluster munitions are munitions composed of a non-reusable delivery body containing multiple, explosive submunitions delivered primarily by aircraft and artillery. The DoD developed cluster munitions during the Cold War to keep Soviet forces out of Western Europe with armor-killing munitions. After the Cold War, cluster munitions delivered by aircraft and artillery were used to great and devastating effect against Iraqi armor formations during Operation Desert Storm proving their destructiveness and their utility as a psychological weapon on enemy troops who witness adjacent units being ravaged by them. Howitzer-launched cluster munitions are the most common type in the U.S. stockpile and can equal the lethal effects of 15 non-cluster munition shells. The advantages of such a munition are obvious. Systems such as this represent a legacy capability of the U.S. Army and Marine Corps, designed to present credible counter-measure to adversaries capable of using large mechanized forces against the U.S. in a combined arms maneuver battle.

Presently, no replacement has been identified for the vast stockpile of howitzer munitions that will be eliminated in just a few years. Unfortunately, the debate within the U.S. military about potential replacements is side-tracked by a widespread perception that wars in which cluster munitions would be useful are a thing of the past so the United States does not need to prepare for them. In other words, many in the defense community seem to believe that the United States is not likely to engage in future conflicts involving large enemy armor and infantry formations. By implication, the United States would then no longer need to be able to saturate a large area with massed artillery fire, as precision fire with fewer cannons will do the job just fine. This camp argues that future state adversaries will not apply combined-arms maneuver against the United States because of our overmatch in technology, particularly in air superiority. They also point to the experiences of the past 13 years of low-intensity warfare as well as seemingly irreversible downward pressure on the U.S. defense budget. But these arguments are flawed. Opponents to a cluster munitions replacement dismiss the capabilities of America’s most dangerous state adversaries. If the DoD does not invest in a replacement capability, it may leave U.S. ground forces at a dangerous disadvantage on future battlefields. Furthermore, cluster munitions have a deterrent effect, without which current and future adversaries may become more aggressive.

The Oslo Treaty

Why are we getting rid of cluster munitions? The decision to eliminate them came when America bought into the Convention on Cluster Munitions signed in Norway in 2008 (Oslo Treaty). The Treaty prohibits signatories from manufacturing, acquiring, distributing, or using cluster munitions. 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. The second aim is to eliminate the large amount of unexploded sub-munitions found in areas where cluster munitions have been fired. Up to 5% of submunitions may not explode when fired, which can wreak havoc on civilian populations for years.

Although the United States is not a signatory to the treaty, both the Bush and Obama Administrations supported the spirit of the treaty. The Bush Administration directed the Department of Defense to implement a policy to meet the intent of the treaty but to do so without giving up the capability while determining how to replace it.

The policy took effect in 2009. All cluster munitions which could not achieve an unexploded ordinance rate of less than 1% (all U.S. cluster munitions) were immediately placed under the release authority of the Combatant Commander. In other words, any usage of these munitions requires the authorization of a four-star general in charge of U.S. military activities in one of six large swaths of the world. No artillery cluster munitions were fired in Operation Iraqi Freedom after the end of major combat operations (declared by President Bush onboard the USS Abraham Lincoln on May 1, 2003) or in Operation Enduring Freedom. The policy gives the services a ten year grace period to design a replacement, conduct research and development, and acquire sufficient new munitions. The services, with the exception of the Army, have failed to accomplish these tasks, despite a clause within the policy that acknowledges the importance of this capability:

[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 U.S. Army has developed a new warhead for its Guided Multiple Launch Rocket System (GMLRS) that is effective against soft-skinned, area targets such as encampments, dismounted infantry, and trucks. 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. The brigade level and below is where dedicated cannon artillery battalions are found and where the vast majority of cluster munitions inventory resides. It is at this level that the tactical fight is conducted and where cluster munitions have the greatest effect in “combined arms maneuver”.

The Impact of Losing Cluster Munitions

Over the past five years the Army has conducted four studies and the Marine Corps has conducted one study to determine the operational risk associated with the loss of cluster munitions. In addition, Norway conducted a study of its own in 2008. While none of the studies are definitive, four of the five American studies found that there is some reduction in U.S. artillery lethality when cluster munitions are removed. But they don’t agree how large that reduction would be: estimates range widely from 4% to 25%. In one 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 fundamental disagreement about the character of future warfare the United States is likely to encounter.

All of the Army studies have assumed a specific type of enemy: hypothetical regional despots with outdated Soviet-era equipment and doctrine updated with lessons learned by Saddam Hussein’s Iraqi Army. In other words, if you have armor, don’t let the U.S. see it and dig in in built-up urban areas. These hypothetical enemies also lack air parity with the United States. All these scenarios assume U.S. air dominance. Therefore, the Army cluster munitions assessments assume there will not be many “area targets” for cannon artillery, leading some people to argue there is no gap that needs to be filled.

None of the Army studies consider the possibility of peer or near-peer competitors. They assume there will be no disruption to the U.S. GPS system. On a strategic level, all of the studies ignore the deterrent effect that U.S. cannon cluster munitions have on potential adversaries’ decision to go to war, or not. 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 show no intent of joining with the United States by eliminating their inventories of cluster munitions.

Furthermore, none of the Army studies offer any qualitative analysis, such as the benefits of using cluster munitions to prepare areas of the battlefield for assault, harassing enemy defenses, denying areas of the battlefield for use by the enemy, enabling fewer howitzers to support units during a battle, or the psychological effect on the enemies’ continued will to fight. The studies are based strictly on quantitative analysis derived from modeling and simulation and therefore provide only numerical results, such as reductions in enemy casualties or increases in friendly losses.

Despite these shortcomings, the studies have validated the U.S. Army’s investment of several billion dollars in precision technology over the past ten years. However, these investments are heavily reliant on GPS technology and assume the availability of GPS signals against all adversaries anywhere, anytime. If adversaries are able to somehow deny the United States the advantage of GPS, the U.S. Army could lose much of its precision advantage it currently enjoys. That said, those advantages are significant and prolific with considerable secondary benefits, such as reducing the risk of collateral damage and civilian casualties. They are integral to the argument against pursuing a cannon cluster munition replacement.

There are three areas of improvement in precision: precision grid location of targets; precision guidance of munitions to a grid location; and the ability of howitzers to determine a precise grid for their own location. These improvements together with the assumption of air dominance and enemy reluctance to mass and maneuver against U.S. forces discussed above, informed the judgment that the loss of artillery cluster munitions would have only a minimal impact. It is important to note that none of these improvements to precision are able to provide a precision location for moving targets, unobserved targets or large massed targets, which are by definition imprecisely located targets.

None of the assessments conducted thus far have included an enemy capable of challenging U.S. air dominance, putting GPS availability at risk, or fielding ground force technology equal or superior to U.S. ground forces. However, the Norwegian assessment conducted in 2008 did consider peer competitors and demonstrated the existence of a significant operational gap if a replacement specific to the target types and conditions discussed above is not acquired.

Filling the Capability Gap

What the Norwegian study showed is that while the combined effects of precision can mostly fill in for what cannon cluster munitions were originally designed for, there remains a clear and distinct combat capability gap: mechanized, armored vehicles that are either moving, unobservable, massed, or in a GPS denied environment. Cluster munitions, with their saturative effects, were designed for exactly this purpose. Furthermore, the effectiveness of engaging hardened targets is reduced when using conventional high explosive artillery projectiles because effects are not dispersed over the area and the penetrating effects are limited unless they achieve a direct hit on the target. 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.

Matching Munitions to Targets and Conditions
Matching artillery munitions to targets and conditions

Thankfully, there may be a means for closing the gap against these target types and conditions. A means that would not require an expensive one-for-one replacement of the cluster munitions stockpile nor necessitate a large investment in research and development. The answer may be sensor-fuzed munitions. This is a family of munitions that are employed by firing them in an area where enemy vehicles are thought to be located; the sensor-fuzed munition seeks 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 a shaped-charge precisely on the target using its own sensors and without reliance on GPS. The United States fielded such a munition to great effect during Desert Storm in the form of SADARM (Sense and Destroy Armor). 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 impractical. Now, that calculus has changed. The number of sensor-fuzed 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 against which it would be needed and the small number of state adversaries capable of using armor against the United States effectively. This solution would do nothing to mitigate the decreased effectiveness against soft area targets, but when combined with the new GMLRS technology the risk could be effectively mitigated.


Cluster munitions, anti-personnel landmines, the Army Tactical Missile System, the A-10 Warthog, are all designed for use against conventional military powers, and they are all disappearing from the U.S. military arsenal. Rivals on the international stage continue to invest in these type capabilities. Will the loss of this suite of legacy Cold War capabilities leave the U.S. military in a disadvantageous position in a future war? Even worse, could it make a future war more likely if potential enemies believe the United States does not have the right weapons for a fight?

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. The sum of U.S. and international assessments have confirmed that technological advancements have 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 an operational gap for our ground forces. 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.


Michael Jacobson is a field artillery capability development analyst at the Army Capability Integration Center at Headquarters, TRADOC. Mike is a field artillery Lieutenant Colonel in the U.S. Army Reserve currently commanding the 55th Special Troops Battalion. The opinions expressed in this article are those of the author and do not reflect the position of the U.S. Government.


Photo credit: The U.S. Army