The Russians are pouring troops into a key sector just southeast of the town of Dobropillia in eastern Ukraine's Donetsk Oblast, threatening to overwhelm Ukrainian defenses and march one settlement closer to Kramatorsk and Sloviansk, the last two big free cities in Donetsk.

But the Russians' push toward Dobropillia isn't without cost. Russian losses in this sector are "colossal," according to the mapper Playfra. And every soldier the Kremlin deploys along the Dobropillia axis is a soldier it can't deploy elsewhere.

And that may help explain why the Russians are falling back in two other key sectors, in northern Donetsk Oblast and in neighboring Dnipropetrovsk Oblast. The Dobropillia axis is the Russians' clear priority. For the Ukrainians, that's an opportunity to attack elsewhere.

Dobropillia, a former mining town with a pre-war population of around 28,000, is now a fortress. It anchors Ukrainian positions along the highway that threads northeast to Kramatorsk.

Russia has attacked here before. In August 2025, Russian troops pushed a salient toward the Dobropillia–Kramatorsk highway, and Ukrainian counterattacks cut it apart. By October that year, President Volodymyr Zelensky put Russian losses on the Dobropillia front at about 13,000.

Ukrainian military analyst Kostiantyn Mashovets describes the push on Dobropillia as the southern flank of a Russian operation to envelop the whole Sloviansk–Kramatorsk urban area. The other approaches are harder going. From the southeast, the Russians are blocked by stubborn Ukrainian forces still clinging to positions in the ruins of Kostiantynivka. From the north, starting this spring, the Ukrainian 3rd Army Corps rolled back 18 months of Russian gains.

For an army that's been struggling to complete its conquest of Donetsk, to say nothing of breaking through in other front-line oblasts, Dobropillia has become the priority.

And that's why the Russians are channeling fresh forces into the Dobropillia sector. Part of the 41st Combined Arms Army and units of its 90th Guards Tank Division are now fighting there, Mashovets wrote on 9 October, and the Russian command keeps feeding fresh assault infantry into the sector through the village of Nove Shakhove despite heavy losses. The open-source account Unit Observer tracked the buildup as early as September.

Potentially tens of thousands of troops from those formations join the main forces of the 2nd and 51st Combined Arms Armies, according to Mashovets, as well as elements of the Russian naval infantry, facing the Ukrainian 1st Azov Corps and 19th Army Corps around Dobropillia.

The reinforcements give Russian commanders more options. Mashovets expects the 51st CAA to push south and southwest of Dobropillia and the 2nd CAA toward Raksha and Sviatohorivka, enveloping the town and cutting its supply routes from Bilozerske before any direct assault. The neighboring 8th CAA is fighting around Kostiantynivka. The Russians' immediate goal is "to maintain this offensive pressure from summer into the fall," Unit Observer wrote, setting conditions for a possible siege of Kramatorsk next year.

The outlook for the Ukrainian defenders of Dobropillia is "worsening," Playfra warned on 13 October:

The Ukrainians aren't without options, Playfra explained. They should double down on their current strategy of saturating the fields around Dobropillia with drones in a ring at least 2 to 3 km deep, forestalling large-scale Russian movements until the winter strips the leaves off the trees, depriving the Russians of their best cover from overhead surveillance. This could buy Dobropillia "much more time," Playfra predicted.

Mashovets puts a date on how long Dobropillia has to hold. If it and Druzhkivka, the town just south of Kramatorsk, hold until mid-to-late December, he wrote, the whole Russian plan for Sloviansk and Kramatorsk would collapse and have to be rewritten almost from scratch.

Help isn't coming

Just don't expect a lot of Ukrainian reinforcements along the Dobropillia axis. Many of Ukraine's best troops are busy attacking.

Taking advantage of the surge of Russian manpower in the direction of Dobropillia, Ukrainian forces have counterattacked where the Russians are weakest: in northern Donetsk Oblast and also in Dnipropetrovsk Oblast, just south of Donetsk.

In months of carefully planned assaults supported by ground robots and intensive drone strikes, Ukrainian forces have liberated hundreds of square kilometers in northern Donetsk and Dnipropetrovsk. The Ukrainian 3rd Army Corps' Operation Vivaldi in northern Donetsk largely removed the immediate northern threat to Sloviansk and neighboring Kramatorsk.

But it didn't do anything to help in the direction of Dobropillia, where the Russians have many more troops, much more firepower, and—equally importantly—a singular focus: closing the southern jaw around the last big free cities in Donetsk.

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Ukraine’s 3rd Army Corps took the lessons of the failed 2023 counteroffensive into Operation Vivaldi. It fought small, and won.

Ukraine has completed its Operation Vivaldi, aimed at protecting its fortress belt cities of Donetsk Oblast, which helped Kyiv preserve the region from Russian occupation for 12 years. Brigadier General Andrii Biletskyi, the commander of the Third Army Corps behind the operation, has reported that the fourth phase secured 101 km² of territory. Among the latest achievements is the liberation of three settlements—Zelena Dolyna, Lypove, and Kolodiazi.

The operation's main objective was to move Ukrainian troops into more advantageous defensive positions, Biletskyi said in the first days after the operation was made public. Vivaldi has now summed up the results of all four phases: Ukraine has established full control over 16 settlements, liberated 277 km² of territory, and inflicted 8,000 casualties on Russian forces.

Ukraine worked against Russia's deadline

During Operation Vivaldi, Ukrainian forces have prevented Russian troops from outflanking the Sloviansk-Kramatorsk agglomeration and cutting the Kharkiv–Sloviansk highway, a key supply route for Ukraine’s forces in Donbas, Biletskyi says.

“We thwarted the offensive of the Zapad grouping and forced it to redeploy some units of the 1st Tank Army, which eased pressure on Kupiansk-Vuzlovyi,” Biletskyi announces.

Previously, the Institute for the Study of War noted that Russian President Vladimir Putin was confident that Russian forces would be able to seize the entire Donetsk Oblast by the end of 2026 — the Kremlin’s latest deadline for achieving this goal.

Ukraine’s military was on a mission to prevent this.

Season one: clearing russian infiltration groups

On 15 September 2026, Ukraine’s Third Army Corps announced Operation Vivaldi in northern Donetsk Oblast. During the first phase, Ukrainian troops cleared Russian groups from 75 km² of territory and liberated another 10 km².

The Third Army Corps said it had struck Russian supply routes and fuel infrastructure, prompting Russia to relocate its fuel and lubricant reserves to Voronezh Oblast. According to the corps, Russian forces lost around 1,500 troops, more than 12,000 drones, and hundreds of pieces of equipment.

Season two: liberation of Shandryholove and Derylove

On 20 September, the Third Army Corps reported the liberation of Shandryholove and Derylove and the establishment of full control over Drobysheve.

During the second season, Russian forces lost another 800 troops, bringing their total losses across the first two seasons to more than 3,000, according to the corps.

During the first two seasons of the operation, Ukrainian troops and attached units regained control of 125 km² of territory, including 50 km² that had been fully liberated.

The first phase of Vivaldi involved eliminating Russian groups that had infiltrated Ukrainian positions, explained the commander of a battalion in the 125th Brigade, callsign Darwin, per ArmyInform. After clearing those groups, the Defense Forces moved on to the operation’s second phase, using reconnaissance drones to detect Russian forces, he added.

For this, Ukraine used UAVs and ground robotic systems.

“The Third Army Corps was the first in the world to begin deploying ground robotic systems by air. Our heavy bombers deliver kamikaze ground robotic systems more than 10 kilometers behind enemy lines,” Biletskyi noted.

Season three: advances near Novе and Ridkodub

On 28 September, the Third Army Corps reported the liberation of Nove, Ridkodub, and Katerynivka and the restoration of control over Karpivka and Novomykhailivka. Ukrainian forces regained another 51 km² of territory, bringing the total area liberated since the start of the offensive to 176 km². Russian forces lost around 2,000 troops, and more than 250 were taken prisoner, the corps said in its summary of the operation’s third phase.

“The Russians were convinced that the main axis of attack was Shandryholove–Zelena Dolyna. This led it to squander its reserves in counterattacks along that very axis. The Russians slept through the actual strike, which was focused on capturing Nove,” Biletskyi said.

Operation Vivaldi aimed to disrupt Russia’s plans in Donetsk Oblast

The need for Operation Vivaldi arose amid Russian attempts to encircle Ukraine’s fortified belt in Donetsk Oblast. Ukrainian forces conducted preparatory efforts aimed at degrading Russia’s offensive capabilities, including strikes on Russian drone operators, the Institute for the Study of War reported on 9 October.

Ukrainian counterattacks in the Lyman direction and east of Sloviansk and Kramatorsk were intended to complicate Russian efforts to seize the fortified belt in Donetsk Oblast, the report noted.

The corps advanced gradually, reclaiming small areas instead of attempting a large-scale breakthrough.

A Russian attack on Sloviansk on 13 October wounded members of a Ukrainian Red Cross team, the Ukrainian Red Cross Society reported. The same day, a Russian bomb hit the city’s invincibility point, one of the state-run hubs where residents warm up and charge phones when power goes out.

Help is getting harder to reach in Sloviansk. Public transport stopped after a Russian strike on two buses in nearby Kramatorsk killed 30 people on 8 October. From 1 November, a curfew from 16:00 to 11:00 will cover nearly all of Donetsk Oblast’s free territory. The people providing help are hit too. Russian drones struck three ambulances in Kramatorsk on 5 October. In August, a Russian strike destroyed a World Health Organization humanitarian warehouse in Dnipro.

Team had moved from Lyman

Three members of the society’s Lyman city branch were hurt. The branch had moved to Sloviansk because of the security situation and kept working there. All three were hospitalized with shrapnel wounds and burns. The building where the team worked took heavy damage, and a fire caused by the attack damaged the organization’s property.

The society’s Donetsk Oblast branch later added that a fourth person suffered a concussion, and that all four were hospitalized. The Red Cross condemned attacks on civilian infrastructure and humanitarian workers.

Bomb hit the warming center

The strike came at 12:45 in the Lisnyi microdistrict, Sloviansk city military administration head Vadym Liakh wrote. He later identified the weapon as a FAB-250, a 250-kg air-dropped bomb. Eight people were injured, and five apartment blocks were damaged, Liakh said. He described the warming center’s building as damaged, while Suspilne Donbas reported it destroyed.

Two Russian strikes on Sloviansk that day killed at least one person, Donetsk Oblast head Vadym Filashkin wrote. Liakh said a Russian attack on the Semenivka neighborhood killed a 55-year-old woman. On 14 October, Filashkin reported that Russian attacks killed three people across Donetsk Oblast on 13 October, in Sloviansk, Druzhkivka, and Starovarvarivka.