Biden will send cluster bombs to Ukraine: What to know about the controversial weapon

U.S. President Joe Biden's decision last week to provide Ukrainian troops with a controversial weapon known as "cluster bombs" ignited swift condemnation from NATO allies and even fellow Democrats.

But as the war in Ukraine rages on after more than 500 days since Russia's invasion, Biden and other security officials have insisted that the ammunition is necessary for Ukraine's counteroffensive campaign to repel the opposing forces.

Biden is in attendance this week at a NATO summit in Lithuania just days after the Pentagon announced Friday that it was supplying 155mm artillery shells containing the cluster munitions to Kyiv as part of its next $800 million weapons package. Many NATO nations are party to a treaty prohibiting the use of the bombs, which can detonate much later and inadvertently kill civilians.

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What are cluster bombs?

Cluster bombs, or cluster munitions, are artillery shells or bombs that disperse smaller weapons known as “bomblets.”

The weapons can be dropped from aircraft or fired from the ground.

A canister skin opens in the air, deploying submunitions of up to 200 bomblets, each of which contain a highly explosive charge. Made from internal notched steel, each submunition breaks into hundreds of pieces that explode when they hit the ground with the potential of disabling vehicles and structures, and even killing people.

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Why is the weapon controversial?

Because deploying cluster munitions increases the potential for indiscriminate civilian casualties, many nations and human rights groups have decried their use.

The "dud" bomblets that don't detonate on impact can essentially become landmines that can explode later and remain lethal for decades.

That's why when Biden and the Pentagon announced that the U.S. would send cluster bombs to aid in the Ukrainian war, the move drew swift condemnation from NATO allies, including Spain and the United Kingdom.

Even some congressional Democrats criticized Biden for the decision, with Rep. Barbara Lee, D-Calif. telling CNN’s “State of the Union” on Sunday that use of cluster bombs is "crossing a line."

Lee was among 19 House progressives who signed on to a letter Friday decrying the move, saying “there is no such thing as a safe cluster bomb.”

Secretary of State Antony Blinken said Tuesday in an interview with MSNBC that Ukraine would be “defenseless” without the cluster munitions. Reiterating the White House explanation that stockpiles of other munitions were running low in the West, Blinken insisted that cluster munitions would fill the gap.

"The hard but necessary choice to give them the cluster munitions amounted to this: If we didn’t do it, we don’t do it, then they will run out of ammunition," Blinken said. "If they run out of ammunition, then they will be defenseless.”

Are cluster bombs banned?

More than 100 countries, including many NATO allies, have banned international use of the weapons by signing the 2010 Convention on Cluster Munitions.

Though 123 nations signed the treaty, the United States, Ukraine and Russia notably have not.

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Russian and Ukrainian forces both have cluster munitions in their arsenals and have used the weapons since the war began in February 2022 following Russian President Vladimir Putin's unprovoked invasion.

The Pentagon maintains that they are a necessary because they allow a smaller force with fewer weapons to take on a larger adversary. And though Biden said he believes that Ukraine's need for the weapons is dire, he conceded in an interview with CNN that sending the weapons was a “very difficult decision.”

How will cluster bombs be used in Ukraine?

Ukraine has pleaded for months for the U.S. to provide the weapons.

The country's forces have made only incremental progress in its counteroffensive launched last month, and U.S. officials hope that the provision of cluster bombs will replenish Ukraine's dwindling artillery and prevent Russia from seizing more territory.

Ukrainian President Volodymyr Zelenskyy wrote in a tweet on Friday that he was grateful for the "broad and much-needed defense aid package" from the U.S. government.

National Security Advisor Jake Sullivan has said Ukrainian officials have provided written assurances that the munitions will be used in a way that minimizes risk to civilians.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com and follow him on Twitter @EricLagatta.