DONETSK REGION, Ukraine — The Ukrainian soldiers felt like they had done everything right. After raking the two squads of attacking Russian troops with their automatic grenade launchers, they sent in the attack drones to pick off the survivors.

But what happened next turned the battle into a math problem. More enemy soldiers arrived, some in armored vehicles. Russian support fire with drones and artillery poured down on the outgunned Ukrainians, said Andrii Bilozir, the senior sergeant for the unit’s first battalion. The soldiers of the 33rd Mechanized Brigade had to withdraw.

“I had the task of saving the boys,” Bilozir said.

Soldiers from several units along the front have described improved Russian tactics this summer that combine their advantages into powerful attacks that Ukrainians have struggled to counteract, even as they achieve local victories. That is apparent in places like Vuhledar, the small Donetsk citadel that fell to Russian forces Tuesday, forcing a Ukrainian withdraw in a hardscrabble town they fiercely defended for two years.

Enemy troops are storming the battlefields in small teams that minimize detection and make return fire difficult, backed by superior quantities of artillery and drones. Russia has also improved its battlefield communication, helping coordinate attacks. While losses are staggering, Ukrainian soldiers have said, the Russians have the numbers to keep up the pressure and Western aid isn’t making up the equipment deficit.

That confluence of factors, combined with Ukraine’s perennial challenge to replenish its combat units and its focus on a large operation inside Russia, has allowed Moscow’s forces to claim territory in the Donetsk region with speed and aggression not seen since the full invasion in 2022. Ukrainian forces have been retreating along dozens of miles of a front line being pushed to its breaking point.

The territorial losses have been glaring this summer. In Vuhledar, Ukrainians imposed heavy losses against previously failed Russian assaults. The 72nd Mechanized Brigade, which had fought there for about two years with no relief, was exhausted but determined, an officer in the unit said, speaking on the condition of anonymity because he was not authorized to speak to reporters.

But artillery volleys in the area sometimes reach 10 shells to 1 in favor of Russia, he said, and glide bombs launched unopposed from jets can destroy whole sections of a trench line and anyone manning them. Moscow’s forces have pushed the 72nd further and further back, the officer said, risking an encirclement of Ukrainian forces.

Asked whether the question is when Vuhledar will fall, rather than if, the officer did not hesitate.

“Yes,” he said.

Days later, his grim prediction became reality. Ukrainian forces withdrew from the town to prevent encirclement and losing troops and equipment, the regional command said Wednesday.

Russian forces gained territory in August and September at a pace not seen since 2022, said Pasi Paroinen, an analyst with Black Bird Group, an open source intelligence analysis collective based in Helsinki. The pressure was mostly felt in the southern Donetsk region. Russian forces in that period increased occupied territory across Ukraine by 318 square miles, Paroinen said — about 268 of which were claimed along the front between Bakhmut and Vuhledar.

The steepest losses of territory occurred from mid-August to mid-September, Paroinen said, coinciding with the Ukrainian incursion into Russia’s Kursk region.

The surprise offensive into Kursk in August that involved 30,000 of Ukraine’s soldiers was partially a bid to peel enemy troops away from their positions on the eastern front. That gambit has not yet paid off, and while invigorating Ukrainian morale, likely contributed to the losses in Donetsk, some analysts have said, because it involves experienced units receiving prioritized resupply and fresh troops that otherwise would have gone to the east.

Kursk has likely stretched Ukrainian personnel thin and exacerbated the manpower issue, already among the main challenges for Kyiv, said Rob Lee, a senior fellow with the Foreign Policy Research Institute. Heavy losses of experienced Ukrainian soldiers, coupled with new troops sped to the front with limited training, have further added pressure on units holding the line.

“A lot of these problems are fundamental problems, and they haven’t been fixed,” Lee said. He said, however, that the situation could improve if Ukraine continues its pace of mobilization, and they may have more operational surprises planned.

But the effects of Russia’s advance are already being felt in the region.

Pokrovsk, a key highway and rail hub central to Ukraine’s efforts to move troops and equipment throughout the southern Donetsk region, has been a focus of attack and civilian evacuations for weeks. The destruction of railways and bridges means it is effectively lost, soldiers have said, forcing longer and more perilous routes through the area.

But the most consequential aspect of the fight along this portion of the Donetsk front may be more about the loss of troops than territory, Lee said. Both Moscow and Kyiv have suffered heavy losses, and the victor could be the side that can hold out the longest.

“At what point does this become unsustainable or lead to political problems for one side?” Lee said. “I think that’s the strategic question here.”

In the field, soldiers are just trying to hold on while adapting to the revised Russian tactics.

The fight last year was largely defined by artillery duels and so-called “meat assaults” of large groups of poorly trained Russian mobilized soldiers. But now Ukrainians report enemy assault troops as often being well trained and well equipped, moving in smaller groups than before. In certain parts of the front line, Russian troops were storming defenses in groups of 10 to 20 soldiers months ago, and are now using teams as small as four, soldiers and analysts said.

The practice helps Russian troops evade surveillance, and their dispersal makes it more difficult to target them with drones and artillery. These assaults, according to numerous reports, are fueled by coercion, with threats of violence or jail if they surrender or retreat.

The small assault team tactic is familiar to Ukrainians, who leveraged the practice last fall in taking back villages held by Russians. But the key difference now, soldiers said, is Russia has combined the concept with its advantages in munitions and a tolerance for losses. New communications equipment has also helped Russian commanders better organize assaults, soldiers have said, and increased the proficiency of drone attacks.

Recently on a training range in the Donetsk region, soldiers from the 68th Jaeger Brigade practiced with U.S.-made .50-caliber and M240 machine guns at night.

The soldiers had just fought north of Selydove, where Russian troops have made gains. Vitalii, a junior lieutenant, described how the small teams of clearly well-trained Russian troops were coming down roads covered by Ukrainian machine guns and getting mowed down.

“They don’t spare people, and their men are forced to move through those paths. And in the last place where we were working, there’s a crossroads completely littered with bodies, and they keep coming, because they have orders,” he said. “There’s already a mass of them. Everything is black with corpses.”

Some Ukrainians are heartened by the large numbers of enemy dead, but that comfort appears to be diminishing, as Moscow willingly sacrifices whole battalions of soldiers for advances.

“It just happens that we constantly need to fall back,” said Vitalii, giving just his first name in accordance with Ukrainian military protocol, “because the Russians have much more strength.”

As the Russians take more ground, the effects are rippling back from the front lines and civilians are fleeing from towns now in range of Russia’s weaponry.

In Myrnohrad, a small town east of Pokrovsk, a small team of construction workers scoured a bombed-out hospital to salvage any functional medical equipment. They paced back and forth, broken glass crunching under their boots, to ready the last piece of hardware - an MRI machine destined for a hospital further from the front.

The Russians destroyed a major bridge nearby, cutting off resupply for Ukrainian units in the area for days, one of the workers said, speaking on the condition of anonymity out of concern of being publicly identified. Soldiers had already been through, looking for syringes, IV bags and other medical supplies, he said. They left behind rooms covered in shattered concrete and folders of doctor’s notes for patients who may never return.

The workers had a tight window to accomplish their salvage at the hospital while Russian forces appeared to be focusing on other targets, he said, desperate to get out of there and rejoin his family before strikes resumed.

“As soon as I finish,” he said, “I will go.”

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