U.S. Cluster Munitions Arrive in Ukraine, but Impact on Battlefield Remains Unclear

U.S. officials and military analysts warn that American-made cluster munitions probably will not immediately help Ukraine in its flagging counteroffensive against Russian defenses as hundreds of thousands of the weapons arrived in the country from U.S. military depots in Europe, according to Pentagon officials.

“The scale of effect will be modest,” said Jack Watling, a senior research fellow at the Royal United Services Institute in London, who has made several trips to Ukraine. “It will make the Ukrainian artillery a little more lethal. The real impact will be felt later in the year when Ukraine has significantly more ammo than would otherwise have been the case.”

Colin H. Kahl, the under secretary of defense for policy, acknowledged last week that “no one capability is a silver bullet,” but said the cluster munitions would allow Ukraine “to sustain the artillery fight for the foreseeable future.”

President Biden had wrestled with a decision for months. Cluster munitions, which have been outlawed by many of America’s closet allies, scatter tiny bomblets across the battlefield that can cause grievous injuries even decades after the fighting ends when civilians pick up duds that did not explode.

Russia has used weapons of this type in Ukraine for much of the war. The Ukrainians have also used them, and President Volodymyr Zelensky had pressed for more in order to flush out the Russians who are dug into trenches and blocking his country’s counteroffensive.

Mr. Biden determined last week that depriving Ukraine of the weapons as it faced dire ammunition shortages would amount to leaving it defenseless against Russia. He said it was a temporary move to hold Ukraine over until the production of conventional artillery rounds could be ramped up.

The decision gives Ukrainian troops more time to probe the Russian defenses for weak spots along three main lines of attack — shelling Russian artillery that attacks their advancing forces — and then punch through dense minefields, tank traps and other barriers. It also allows the Ukrainian Army to do more of what it knows best — fire thousands of artillery shells a day to wear down Russian defenders.

“It looks like they’re back to an artillery duel,” said Amael Kotlarski, a weapons team manager at Janes, the defense intelligence firm.

But that artillery-centric approach raises questions about whether Ukraine has lost confidence in the combined arms tactics — synchronized attacks by infantry, armor and artillery forces — that nine new brigades learned from American and other Western advisers in recent months. Western officials heralded the approach as more efficient than the costly strategy of wearing Russian forces down by attrition and depleting their ammunition stocks.

Senior U.S. officials in recent weeks had privately expressed frustration that some Ukrainian commanders, exasperated at the slow pace of the initial assault and fearing increased casualties among their ranks, had reverted to old habits — decades of Soviet-style training in artillery barrages — rather than sticking with the Western tactics and pressing harder to breach the Russian defenses.

When asked about the American criticism, Andriy Zagorodnyuk, a former Ukrainian defense minister who advises the government, said in an email: “Why don’t they come and do it themselves?”

Biden administration officials are hoping the nine brigades, some 36,000 troops, will show that the American way of warfare — using combined arms, synchronized tactics and regiments with empowered senior enlisted soldiers — is superior to the rigidly centralized command-structure that is the Russian approach.

“It pushes them out of their comfort zone a little bit because this has them employing fire and maneuver in a way that’s more familiar to NATO forces than the kind of forces that have a Soviet legacy and Soviet doctrine behind them,” Mr. Kahl said. “It is requiring them to fight in different ways.”

With a vast new supply of artillery rounds now at the Ukrainians’ disposal, the pressure to fight like Western armies has eased. But Mr. Kahl and other top U.S. policymakers and senior uniformed officers said it was too soon to judge the counteroffensive and how the Ukrainians will wage the fight.

“It is slower than we had hoped, but the Ukrainians have a lot of combat power left,” Mr. Kahl said, noting that the bulk of the nine Western-trained brigades has yet to be committed to the fight and is being held in reserve for when Ukrainian troops can pour through holes punched through the Russian defenses.

“The real test will be when they identify weak spots or create weak spots and generate a breach, how rapidly they’re able to exploit that with the combat power that they have in reserve and how rapidly the Russians will be able to respond,” Mr. Kahl said.

American and Ukrainian military officials have declined to say exactly how Ukraine will use the cluster munitions, which are U.S.-made M864 155-millimeter artillery shells that can be fired from howitzers and release 72 small grenades once over their target.

“I don’t think there will be that much of an immediate effect,” said Rob Lee, a Russian military specialist at the Foreign Policy Research Institute in Philadelphia and a former U.S. Marine officer.

Mr. Lee said Ukraine would probably try to use the cluster munitions near sections of the 600-mile front lines where it was less likely to send troops to avoid putting its forces at risk.

The United States will work with Ukraine to minimize the risks associated with the weapons, Mr. Kahl said. Specifically, he added, the Ukrainian government has said that it would not use the rounds in densely populated urban areas, and that using the rounds would make demining efforts easier after the conflict.

“Cluster munitions will be used only in the fields where there is a concentration of Russian military,” Ukraine’s defense minister, Oleksii Reznikov, said in a Twitter message last week. “They will be used to break through the enemy defence lines with minimum risk for the lives of our soldiers. Saving the lives of our troops, even during extremely difficult offensive operations, remains our top priority.”

Mark F. Cancian, a former White House weapons strategist who is now a senior adviser at the Center for Strategic and International Studies in Washington, said, “Cluster munitions will not only provide enough shells to continue the high level of artillery fires but provide a more effective munition against area targets such as infantry, artillery, and truck convoys.”

The munitions are arriving at a time when Ukrainian troops are slowly grinding forward.

Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, said last month that Ukraine was “advancing steadily, deliberately working its way through very difficult minefields” at some 500 to 2,000 yards a day. “Slow advance is very deliberate,” General Milley said. “That is happening.”

He added that the fact that the long-awaited push to recapture occupied territory was not advancing as rapidly as many experts had predicted “doesn’t surprise me at all.”

“It’s going to be very long, and it’s going to be very, very bloody, and no one should have any illusions about any of that,” General Milley said. “At the end of the day, Ukrainian soldiers are assaulting through minefields and in the trenches, and this is literally a fight for their life. So yes, sure, it goes a little slow, but that is part of the nature of war.”