What are Cluster Munitions?

Cluster munitions are all over the news since the Biden Administration made the decision to provide them to Ukraine for use against Russia. The agreement represents a significant upgrade in US weapon systems sent to the war zone. Cluster munitions evoke strong opinions from their proponents, as well as those who believe they should be outlawed. With that in mind, let’s look at what cluster munitions are, how they work, and why they are banned in 123 countries.

M984 DPICM mortar shell diagram
This M984 CPICM extended range mortar shell is a common cluster munition. (L3 Communications)

Cluster Munitions

Cluster munitions are simply artillery shells, bombs, or rocket warheads that break open, scattering clusters of smaller “bomblets,” or submunitions, over a wider area than might be affected by a single bomb or projectile. The individual bomblets pack less power than a regular shell or bomb, but together, they can be devastating.

The bomblets can be configured as shaped charges for use against armor or for fragmentation against enemy personnel. The delivery shell, bomb, or warhead usually breaks apart in the air, scattering the bomblets, which feature stabilizing fins or streamers to ensure the business end arrives first. This is especially important for anti-armor missions. If the shaped charge faces the wrong way, it will not penetrate the target. The bomblets can be set to explode on impact or in the air. Fragmentation is particularly deadly as an airburst, raining hot steel shrapnel onto enemy troops, and partially overcoming dug-in fighting positions.

DPICM cluster munition cutaway diagram
(US Department of Defense)

Some submunitions are incendiary in nature, meaning they start fires using white phosphorus or napalm, particularly in enemy cities. They have also been used to devastate vegetation, thus denying cover to enemy troops.

These weapons are officially known in the US as Dual Purpose Improved Conventional Munitions (DPICM). The term “Dual Purpose’ refers to their ability to effectively engage both armor and personnel. They can also be armed with delayed fuses, allowing their users to interdict enemy forces with what are essentially artillery or air-deployed minefields. The delayed fuses can be timed, set to explode upon contact, or if they are tampered with.

Ukraine has pressed the United States for DPICMs to help them overcome strong Russian defensive networks in the occupied East. Properly deployed DPICMs can make simple trench systems untenable and complicate Russian reinforcement efforts through interdiction.

Nothing New

The first widely used cluster munition was the German “Butterfly Bomb” of World War II. The United States, Italy, and the Soviet Union also developed such weapons during the war. Both sides attacked cities with incendiary cluster bombs. Notable examples are the Allied fire bombings of Dresden and Tokyo. Germany used delayed fuse fragmentation cluster bombs during the London Blitz to hamper firefighting efforts.

US forces liberally employed cluster munitions in Korea and Vietnam, particularly anti-personnel and incendiary types. Hundreds of millions of submunitions were deployed against Vietnam, Cambodia, and Laos between 1964 and 1973. Cluster munitions reached their height, in terms of worldwide deployment, from the early 1970s through the 1990s.

Cluster bomb on a Korean target range
A cluster bomb hitting a Korean target range. (Republic of Korea Air Force)

Double-Edged Sword

DPICMs, however, also carry certain risks to their users. The DPICMs being sent to Ukraine are intended for the long-expected offensive against Russian positions. The Russian Army has had plenty of time to prepare, including constructing formidably dug-in fighting positions. Observers expect the Ukrainian attackers will rely heavily on artillery, including DPICM rounds.

If the Ukrainians achieve a breakthrough, or even just push the Russians back, their troops will be walking into minefields created by their own artillery. And that reality will not only be restricted to rounds fired for that purpose. DPICMs always have a few bomblets that don’t explode. This unexploded ordnance (UXO) still represents a threat, since its failure is often merely a fuse problem.

Militaries, analysts, and activists measure failure rates, or “dud rates,” for cluster munitions. These rates vary among nations, as manufacturing standards, procedures, and quality control can vary significantly. US National Security advisor Jake Sullivan says American DPICMs’ dud rate is at or below 2.35%, though the acceptable rate has recently been raised from the previous standard of 1%. A recent report to Congress, however, as reported by multiple media outlets, indicates that cleanup operations “have frequently reported failure rates of 10% to 30%.”

Explosive ordnance disposal technician disarming an unexploded DPICM artillery shell.
Dealing with dud DPICM rounds requires skilled technicians and specialized equipment. (acc.af.mil)

Russian cluster munitions are reportedly even less efficient, with a dud rate of 30 to 40%. The Russian Army has used the weapons extensively during the Ukraine War, a fact used to justify previously restricted American sales and Ukrainian deployment of DPICMs. Whether that justification holds water is open to debate, but a Ukrainian offensive would undoubtedly be far more difficult without them.

Controversial Weapons

I say “justify” because cluster munitions’ dud rate makes them extremely dangerous not only for soldiers, but also for civilians. The submunitions are comparatively small and can lie undetected for a long time after the fighting has passed, just as more conventional UXO (unexploded ordnances) has done from both World Wars. France still contains about 40 square miles of restricted Zones Rouge (Red Zones) where hundreds of tons of unexploded World War I artillery shells, bombs, and grenades are dug up each year. World War I ended in 1918. The French Sécurité Civile, which removes any uncovered UXO, estimates that complete removal could take up to 700 years. In Southeast Asia, UXO has killed or injured some 7,000 people since 2009 in Vietnam’s Quang Tri province alone.

French Zones Rouge map
Experts estimate that clearing France’s Zones Rouge will require another 700 years. (Guicherd, J. & Matriot, C., via Journal d’Agriculture Pratique 34 (1921))

The extended dangers to civilians are so great that 123 nations have signed the Convention of Cluster Munitions, an international treaty outlawing weapons such DPICMs. The treaty has been in effect since 2008. Neither Russia, Ukraine, nor the United States is party to the treaty, though most NATO countries are. The treaty requires signees “never under any circumstances to:”

  • Use cluster munitions;
  • Develop, produce, otherwise acquire, stockpile, retain, or transfer to anyone, directly or indirectly, cluster munitions;
  • Assist, encourage, or induce anyone to engage in any activity prohibited to a State party under this Convention.

Despite not signing the treaty, the US and Ukraine acknowledge the dangers of cluster munitions. The US sale requires the Ukrainians to record and map areas where DPICMs are deployed. It also requires a commitment to cleaning them up if and when they recover that territory. Cleanup is hazardous and expensive, requiring highly trained personnel and specialized equipment. Even then, the detection rate will not be 100%. If Ukraine does not recover those areas, it will be the Russians’ problem.

A Necessary Evil?

Warfare is always ugly. It is also sometimes necessary. Regardless of one’s position on whether the US should support Ukraine, the fact remains that Russia invaded a sovereign nation unprovoked. The Ukrainians have every right and obligation to defend themselves. If Ukraine wants to attack the entrenched Russian troops, the DPICMs offer clear advantages over conventional artillery shells or bombs, which must hit exactly right to be effective. That isn’t likely.

DPICM function diagram - cluster munitions
DPICMs are effective, though controversial, weapons. (RDECOM)

Cluster munitions are proven, effective modern battlefield tools. Like any weapon, they carry a cost. Whether their benefits outweigh those costs cannot be determined by an armchair strategist like me. One can certainly respect those nations committed to not using such weapons. One can also understand why Ukraine believes they need those same weapons. If they are indeed deployed, as seems certain at this point, we can only hope that Ukraine approaches the aftermath responsibly. Either way, Northern and Eastern Ukraine will likely have its own Zones Rouge for years to come.

William "Bucky" Lawson is a self-described "typical Appalachian-American gun enthusiast". He is a military historian specializing in World War II and has written a few things, as he says, "here and there". A featured contributor for Strategy & Tactics, he likes dogs, range time, and a good cigar - preferably with an Old Fashioned that has an extra orange slice.

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