CNN  — 

The United States has confirmed it will supply cluster munitions to Ukraine as part of a new military aid package.

CNN first reported last week that US President Joe Biden’s administration was strongly considering approving the transfer of the controversial weapons to Ukraine, whose forces have been struggling to make major gains in a weeks-long counteroffensive.

Here’s what you need to know about the weapons – and why they are controversial.

What is a cluster munition?

Cluster munitions, also called cluster bombs, are canisters that carry tens to hundreds of smaller bomblets, also known as submunitions. The canisters can be dropped from aircraft, launched from missiles or fired from artillery, naval guns or rocket launchers.

The canisters break open at a prescribed height, depending upon the area of the intended target, and the bomblets inside spread out over that area. They are fused by a timer to explode closer to or on the ground, spreading shrapnel that is designed to kill troops or take out armored vehicles such as tanks.

A cluster bomb capsule at the frontline city of Avdiivka, Ukraine on March 23, 2023.

What type of cluster bomb is the US said to be giving to Ukraine?

The US has a stockpile of cluster munitions known as DPICMs, or dual-purpose improved conventional munitions, that it no longer uses after phasing them out in 2016.

According to an article on the US Army’s eArmor website, the DPICMs Washington will give to Kyiv are fired from 155mm howitzers, with each canister carrying 88 bomblets. Each bomblet has a lethal range of about 10 square meters, so a single canister can cover an area up to 30,000 square meters (about 7.5 acres), depending upon the height it releases the bomblets.

The bomblets in a DPICM have shaped charges that, when striking a tank or armored vehicle, “create a metallic jet that perforates metallic armor,” the article says, adding that it can take 10 or more bomblets to destroy an armored vehicle, but it may take only one to disable the armored vehicle’s weapons or render it immobile.

What are cluster munitions?

Cluster munitions contain multiple explosives that are released over an area up to the size of several football fields. They can be dropped from a plane or launched from the ground or sea.

The submunitions are released in flight and fall to the ground. They can range from the tens to many hundreds

They are designed to explode on impact but as many as a third don’t, and remain a deadly risk to civilians for years to come

94% of recorded cluster bomb casualties are civilians, of which almost 40% are children

Note: Cluster munitions can vary widely in design and scale, this graphic only aims to explain their general function.

Source: Geneva International Centre for Humanitarian Demining, Cluster Munition Coalition
Graphic: Connie Chen and Henrik Pettersson, CNN

Have cluster bombs been used in the war in Ukraine before?

Yes, both the Ukrainians and the Russians have used cluster bombs since Moscow’s forces invaded in February 2022. More recently, Ukrainian forces have begun using Turkish-provided cluster munitions on the battlefield.

But Ukrainian officials have been pushing the US to provide its cluster munitions since last year, arguing that they would provide more ammunition for Western-provided artillery and rocket systems, and help narrow Russia’s numerical superiority in artillery.