The images of Russian troops retreating from a village in Ukraine under fire leave little doubt of the impact of cluster munitions. Soldiers running from a constellation of at least a dozen explosions around them. An armored vehicle speeding down a road before being hit in a cascade of simultaneous eruptions salting the surrounding ground.
The August drone footage of the Russian withdrawal from the southeastern village of Urozhaine, verified by The New York Times, highlights the power of the weapons. But their usage also points to a grim trade-off in the 18-month conflict. By embracing cluster munitions to keep this summer’s counteroffensive moving forward, Ukraine and the United States have opened themselves to human rights concerns about their long-term threat to civilians who inadvertently trigger unexploded bombs.
Now, two months after the United States shipped an initial tranche of the munitions to Ukraine to ensure its troops did not run out of ammunition, three American officials said the Biden administration is planning to send more, and soon.
One official said the weapons were key to helping Ukraine maintain the momentum its troops just recently gained on the southern front against Russian forces. All three of the officials spoke on condition of anonymity to describe internal discussions.
President Biden’s decision this summer to send the munitions to Ukraine, after pleas by President Volodymyr Zelensky, drew widespread condemnation, and even some close American allies were critical.
Both Russia and Ukraine used the bomblets during the 18-month war well before the American shipment arrived in mid-July, but with a crucial distinction. Russia has used them against a country it had invaded, where its forces have not hesitated to wreak indiscriminate destruction, while Ukraine has used them on its own soil, weighing the costs to its own people.
Cluster munitions have been banned by more than 100 countries because of their devastating effects, sometimes years later, on children and other civilians who mistakenly disturb and detonate unexploded rounds.
Some Ukrainian troops said U.S.-supplied cluster munitions have been a powerful addition to a slew of weapons the West has sent for the counteroffensive, and a necessary substitute for their dwindling stocks of 155-millimeter artillery shells.
“They are super efficient,” said one Ukrainian marine, who participated in the successful fight for Urozhaine and who identified himself only as Serhiy. “When our guys see how we use them against the enemy, their spirits soar.”
But other Ukrainian soldiers are more measured, saying cluster munitions are used mostly in situations where enemy infantry are exposed, and that they are largely ineffective against the dug-in Russian positions — line after line of trenches and bunkers — that are the major obstacle to the counteroffensive.
Western officials and experts agree that cluster munitions — multiple bomblets packed in shells that disperse over a wide area before impact — are most effective against forces and vehicle convoys that are spread out over open terrain. Because the bomblets leave the shells in a scattershot way, it is hard to direct them at precise targets.
So far, American officials said, they have been used to strike concentrations of Russian troops, artillery systems, air defenses, ammunition depots, radar stations and vehicles.
“What we have seen from Ukrainian reporting is that they are having good effect with this capability,” Laura K. Cooper, a U.S. deputy assistant secretary of defense for Russia, Ukraine and Eurasia policy, said in a recent interview.
U.S. officials will not say how many cluster munitions were included in the first shipment, out of the hundreds of thousands that the Pentagon has available.
The American-supplied cluster munitions are fired from 155-millimeter howitzers, with a range of about 15 miles. Some military experts are now pushing for cluster munitions that can be launched from rocket systems and hit targets dozens of miles away.
With NATO states’ stockpiles of other ammunition to donate running alarmingly low, and with weapons manufacturers in the United States and Europe unable to keep up, experts said cluster munitions may be one of the only available means to refill Ukraine’s supply.
Ukraine’s voracious demand for ammunition is expected to rise as some units increasingly rely on heavy artillery to lay the ground for infantry advances instead of NATO-style combined arms warfare that Ukrainian units have struggled to master.
U.S. officials have estimated that Ukrainian forces were recently firing as many as 8,000 artillery rounds each day — including hundreds of cluster munitions.
Taken together, that could lead to cluster munitions becoming what George Barros at the Institute for the Study of War, a Washington-based think tank, predicted could be a “permanent fixture within the Ukrainian arsenal.”
That is especially worrisome to those who object to any cluster munitions being given to Ukraine, no matter who uses them, or how.
“What we’ve seen is that Ukraine is keen to show that there is military utility to cluster munitions,” said Mary Wareham, advocacy director of the arms division at Human Rights Watch. “But at the end of the day these weapons are prohibited because of the harm inflicted on civilians both when they’re used and decades after.”
But without them, Ukraine’s leaders counter, they cannot match Russian firepower.
“I want to look at this from a perspective of fairness,” Mr. Zelensky said in July at the annual NATO summit in Vilnius, Lithuania. “Russia’s constantly using cluster munitions on our territory, and they’re fighting only on our land. They’re killing our people.”
The strategic problem is that in the counteroffensive, Ukraine is fighting dug-in defenders, where cluster munitions “have their limits,” said Can Kasapoğlu, director of defense research at the independent Centre for Economics and Foreign Policy Studies in Istanbul. They may succeed when used with other kinds of artillery, but alone, “they’re not a magic wand,” Mr. Kasapoğlu said.
Gian Luca Capovin and Alexander Stronell, analysts with the British security intelligence firm Janes said in August that Ukraine’s use of cluster munitions in the Donetsk and Zaporizhzhia regions, at least so far, “did not deliver any decisive effect.”
As a condition of receiving cluster munitions from the United States, Mr. Zelensky and senior Ukrainian defense officials pledged to avoid firing them into areas where civilians could be hit.
Senior Russian officials, commanders and military bloggers on the front lines have for months accused Ukraine of firing cluster munitions not only at Russian troops, but also at areas populated by civilians.
The United States has dismissed such claims as disinformation. There has been evidence earlier in the war, however, that Ukraine appeared to sometimes use cluster munitions in populated areas.
For now, Ukrainian forces say the arrival of American cluster munitions had not only raised morale, but also helped to pick apart Russian defensive positions in the south, keep pressure on Russian troops in the east and hold back Russian assaults in the northeast.
And some experts point to some specific battles where they argue the cluster munitions have helped. One of those places is the small city of Kupiansk in Kharkiv Province, where Ukraine has used them in defense more than offense.
Ukraine has struggled for months to maintain control of Kupiansk in the face of a Russian advance. Losing it now would be a major blow, said Mr. Kasapoğlu, who is also a senior fellow at the Hudson Institute in Washington and has been monitoring ground reports from Kupiansk on social media and other public sources.
Within two weeks of Mr. Biden’s decision to send cluster munitions to Ukraine, they reached Kupiansk. By early August, the weapons were targeting Russian forces and armored vehicles trying to seize territory, Mr. Kasapoğlu said.
The fighting in Kupiansk remains fierce. But so far, at least, Ukraine is holding the line, and Mr. Kasapoğlu said that “cluster munitions have indeed played a major role.”
Lara Jakes reported from Rome, and Eric Schmitt from Washington. Thomas Gibbons-Neff contributed reporting from Kyiv, Ukraine, and Marc Santora from southern Ukraine.