The total number of Ukrainian and Russian troops killed or wounded since the war in Ukraine began 18 months ago is nearing 500,000, U.S. officials said, a staggering toll as Russia assaults its next-door neighbor and tries to seize more territory.
The officials cautioned that casualty figures remained difficult to estimate because Moscow is believed to routinely undercount its war dead and injured, and Kyiv does not disclose official figures. But they said the slaughter intensified this year in eastern Ukraine and has continued at a steady clip as a nearly three-month-old counteroffensive drags on.
Russia’s military casualties, the officials said, are approaching 300,000. The number includes as many as 120,000 deaths and 170,000 to 180,000 injured troops. The Russian numbers dwarf the Ukrainian figures, which the officials put at close to 70,000 killed and 100,000 to 120,000 wounded.
But Russians outnumber Ukrainians on the battlefield almost three to one, and Russia has a larger population from which to replenish its ranks.
Ukraine has around 500,000 troops, including active-duty, reserve and paramilitary troops, according to analysts. By contrast, Russia has almost triple that number, with 1,330,000 active-duty, reserve and paramilitary troops — most of the latter from the Wagner Group.
The Biden administration’s last public estimate of casualties came in November, when Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, said that more than 100,000 troops on each side had been killed or wounded since the war began in February 2022. At the time, officials said privately that the numbers were closer to 120,000 killed and wounded.
But that number soared in the winter and spring, as the two countries turned the eastern city of Bakhmut into a killing field. Hundreds of troops were killed or injured a day for many weeks, U.S. officials said. The Russians took heavy casualties, but so too did the Ukrainians as they tried to hold every inch of ground before losing the city in May.
The opening weeks of Kyiv’s counteroffensive this summer were particularly difficult for Ukraine. In the early phase, Western-trained Ukrainian troops struggled to employ “combined arms maneuvers” — a method of fighting in which infantry, armor and artillery are used together in synchronized attacks.
Ukrainian troops initially tried to break through dug-in Russian lines with mechanized combined arms formations. Equipped with advanced American weapons, the Ukrainians nonetheless became bogged down in dense Russian minefields under constant fire from artillery and helicopter gunships.
In the first two weeks of the counteroffensive, as much as 20 percent of the weaponry Ukraine sent to the battlefield was damaged or destroyed, according to U.S. and European officials. The losses included some of the formidable Western fighting machines — tanks and armored personnel carriers — that the Ukrainians were counting on to beat back the Russians.
More significantly, thousands of troops were killed or wounded, officials said.
A senior U.S. official acknowledged the high number of Ukrainian casualties but said combined arms is “very, very hard.” He added that in recent days, Ukrainian troops have begun to punch through initial rings of Russian defenses.
In recent weeks, Ukraine has shifted its battlefield tactics, returning to its old ways of wearing down Russian forces with artillery and long-range missiles instead of plunging into minefields under fire.
American officials are worried that Ukraine’s adjustments will race through precious ammunition supplies, which could benefit President Vladimir V. Putin of Russia and disadvantage Ukraine in a war of attrition. But Ukrainian commanders decided the pivot reduced casualties and preserved their frontline fighting force.
American officials say they fear that Ukraine has become casualty adverse, one reason it has been cautious about pressing ahead with the counteroffensive. Almost any big push against dug-in Russian defenders protected by minefields would result in huge numbers of losses.
In just a year and a half, Ukraine’s military deaths have already surpassed the number of American troops who died during the nearly two decades U.S. units were in Vietnam (roughly 58,000) and about equal the number of Afghan security forces killed over the entire war in Afghanistan, from 2001 to 2021 (around 69,000).
The number of dead and wounded reflects the amount of lethal munitions being expended by both sides. Thousands of rounds of artillery are fired every week, tanks batter buildings, land mines are everywhere and drones hover overhead picking off troops below. When close combat does occur, it resembles the battles of World War I: brutal and often taking place in trenches.
The numbers also point to a lack of rapid medical care on the frontline. Wounded soldiers are increasingly hard to evacuate given how much artillery and gunfire bookend each engagement. Unlike the U.S. wars in Afghanistan and Iraq, where American forces strictly adhered to evacuating casualties within an hour to a well-stocked medical facility, there is no such capability in Ukraine.
Instead, injured troops are often thrown into any vehicle available or leave the front on foot. In some cases, the wounded and dead are left on the battlefield, because medics are unable to reach them. Hospitals and aid stations are often overwhelmed.
And across Ukraine, in big cities and rural villages, almost everyone knows a family that has lost someone in the fighting. Dry flowers from funerals litter quiet roads, and graveyards are filling up in every corner of the country.
The estimated figures for Ukraine and Russia are based on satellite imagery, communication intercepts, social media and news media dispatches from reporters in the country, as well as official reporting from both governments. Estimates vary, even within the U.S. government.
According to Pentagon documents leaked in the spring, Russia had suffered 189,500 to 223,000 casualties, including up to 43,000 killed in action. One document said that as of February, Ukraine had suffered 124,500 to 131,000 casualties, with as many as 17,500 killed in action.
While several U.S. officials and one former senior Ukrainian official said about 70,000 Ukrainian soldiers had died in the conflict so far, other American officials said the number could be lower.
The estimates vary so widely partly because of Ukraine’s reluctance to disclose its wartime losses even to the American government. U.S. intelligence analysts have also spent much more time focusing on Russian casualties than those of Ukraine, their ally.
Russia analysts say the loss of life is unlikely to deter Mr. Putin. He has no political opposition at home and has framed the war as the kind of struggle the country faced during World War II, when more than eight million Soviet troops died. U.S. officials have said they believe that Mr. Putin can sustain hundreds of thousands of casualties in Ukraine, although higher numbers could cut into his political support.
While Mr. Putin appears somewhat reluctant to initiate a widespread mobilization, he has raised the upper age limit for men eligible to be conscripted into the army. And should Russia decide to mobilize more people, its larger population could quickly overwhelm Ukrainian reserves of manpower.
The troop deaths could have a greater impact for Ukraine in a war that is far from over. And while combatants are dying in droves, the civilians caught between the guns have died in the thousands while millions have been displaced.
“These are people,” said Evelyn Farkas, a former top Pentagon official for Ukraine who is now the executive director of the McCain Institute.
“Ukraine is a democracy, so the loss of lives could have greater political impact,” Dr. Farkas said. “But even in an autocracy, Vladimir Putin knows that public sentiment can make a difference.”
Andrew E. Kramer contributed to this report.