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.

Russia lost almost 300 km² of Ukrainian territory on net between March and September 2026, and it likely gained no ground in September despite its heaviest casualties of the year, the Institute for the Study of War (ISW) assessed. Ukraine's Operation Vivaldi accounts for much of the swing. The think tank notes that Ukraine's secrecy around such counterattacks makes exact monthly tallies hard.

Russia has pressed attacks along the entire front through 2026, accepting mass casualties for marginal ground, and its battlefield year has already been called its worst since 2023. Its losses have been outpacing its recruitment for months.

Russia came out behind in September

Russian forces seized 175.54 km² in September but lost 256.35 km², a net loss of 80.81 km², or minus 2.69 km² a day, ISW calculated. The balance stayed negative when Russian infiltrations into areas Russia does not control are counted: Russia seized or infiltrated 143.2 km² but lost 318.38 km², a net loss of 175.18 km².

The September figures include at least 147 km² near Lyman that Ukraine liberated over earlier months, but that ISW recorded only once details of Operation Vivaldi emerged in September. The operation already disrupted Russia's plan to encircle the Fortress Belt cities from the Lyman and Dobropillia directions.

Almost 300 km² lost since March

Russia's rate of seizing territory dropped sharply in March 2026 and has stayed low, or even negative, since, ISW found. After controlling for the gains Ukraine made during Vivaldi, Russia lost control of 293.59 km² net across the front since March. Counting infiltrations, it gained a presence in only 174.44 km² over the same period.

ISW's monthly chart shows net Russian losses of 116.01 km² in April and 281.1 km² in May, modest gains in June, July, and August, and a net loss again in September. Oleksandr Syrskyi, then Ukraine's commander-in-chief, reported in June that Ukrainian forces had recaptured 100 km² in May.

More than 46,000 casualties for no ground

Russian forces suffered 46,230 casualties in September, Ukraine's General Staff reported. It is the third straight month above 40,000 and the highest monthly toll of 2026, by Kyiv's count. Monthly Russian casualties have climbed from 32,980 in April to 42,860 in July and 42,020 in August, ISW's chart shows.

Russia keeps suffering heavy personnel losses while making extremely limited or even net-negative territorial gains, ISW said, and its current force generation system still recruits fewer soldiers than it needs to replace them.

Ukraine's effective operational security around Vivaldi, likely to continue in future counterattacks, will make meaningful month-to-month assessments of Russian gains and losses hard, the think tank added.

Bulgaria gave Ukraine 110 BTR-60 armored personnel carriers. They are 1960s vehicles, too thinly armored to carry infantry anywhere near a front line patrolled by explosive drones. So Ukraine's 3rd Army Corps found another use for them during Operation Vivaldi, its counteroffensive north of Lyman. Fill one with anti-tank mines, rig it for remote control, drive it at a Russian bunker, and set it off.

Packing potentially dozens of TM-62 anti-tank mines, the speedy BTR-60s become what's called vehicle-borne improvised explosive devices, or VBIEDs. Once a favorite weapon of insurgents battling US forces in Iraq and Afghanistan, VBIEDs have found a new niche in Russia's wider war on Ukraine as unmanned demolition systems.

"To break through the enemy's defenses, the 3rd Army Corps employed its own invention, Soviet BTR-60s converted into robotic kamikaze complexes," the corps stated. "They were used to demolish the enemy's strongest fortifications." If an enemy strongpoint is too heavily protected to bomb from the air but exposed to attack from the ground, send in a VBIED.

Білецький: «Противник був введений в оману і проспав справжній удар»

Третій армійський корпус звільнив Нове, Рідкодуб і Катеринівку та відновив контроль над Карпівкою і Новомихайлівкою. Втрати противника — 2000 живою силою, понад 250 росіян захоплені в полон. Так закінчився… pic.twitter.com/GSV4LFG3gj

— Третій армійський корпус (@ab3army) September 28, 2026

The Russians were the first to deploy vehicular IEDs in the current war, but the Ukrainians may have mastered the tactic. It's one thing to rig an explosives-filled MT-LB tractor or T-55 tank to roll straight forward without direct human control, as the Russians once did. It's another to rig an explosive BTR-60 to maneuver before going off, as the 3rd Army Corps' VBIEDs clearly did.

On 28 September, announcing the close of Vivaldi's third phase, the 3rd Army Corps released drone footage depicting one of the explosive BTRs blasting a Russian strongpoint north of the town of Lyman. The sheer scale of the explosion is testimony to the VBIED's destructive potential. And the trail the BTR leaves in the grass in the heavily edited video indicates the Ukrainians can steer their VBIEDs around obstacles and guide them to precision strikes.

Why it gets there

A slow wheeled vehicle crossing open ground toward a fortified position should not survive the trip. In most sectors it would not. What makes the tactic work north of Lyman is a condition the 3rd Army Corps built into Vivaldi before its assault groups moved: Ukrainian air defense and electronic warfare threw a protective dome over the battle area, blinding Russian drones so they could not read the operation's design or strike what was moving through it.

Robots have played critical roles in each phase of Vivaldi. Surveillance drones have watched from overhead. One-way attack drones have pummeled Russian positions and supply lines. Heavy bomber drones have not only dropped bombs, they've also airlifted explosive unmanned ground vehicles into position so the UGVs can roll right through the front doors of Russian bunkers.

The self-exploding BTR-60s are too big to airlift, but that's the point. A small UGV might carry a few tens of kilograms of explosives. A remote-controlled BTR-60 can easily haul hundreds of kilograms.

The arithmetic

It's not impossible to take out a VBIED before it strikes, of course. Mines, anti-tank missiles, and even concentrated gunfire can stop a vehicular bomb in its tracks. But losing one of the aged BTR-60s costs Ukraine very little. The vehicles are too thinly armored for use as front-line infantry transports anyway. You might as well convert them into bombs.

That is the whole case for the tactic. A manned fighter jet lobbing a precision glide bomb is the preferred approach to bunker-busting. But it costs tens of thousands of dollars an hour to keep a jet in the air, and a single glide bomb can cost tens of thousands or even hundreds of thousands of dollars. It's unclear how much it costs to convert a BTR into a VBIED. It could be just a few thousand.

And it reduces Russian fortifications without risking any Ukrainian lives. That's the philosophy underpinning all of the 3rd Army Corps' robot-first tactics. "This is exactly the direction of the corps' development set by Brig. Gen. Andrii Biletskyi," the corps stated, "to reduce the number of fighters in the most dangerous areas and replace them with robots."

Vivaldi began in mid-April under an information blackout that held for five months. The corps says it has regained control of 176 sq km across three of a planned four phases, around half of that de-occupied outright, and taken more than 250 Russian prisoners. Those figures are the corps' own and have not been independently verified.

Sometimes the robots doing that work are 60-year-old APCs modified for an explosive one-way mission.

Ukraine likely neutralized Russia's drone defenses north of Lyman before sending armor into the third phase of its Vivaldi counteroffensive, the Institute for the Study of War (ISW) assessed. An intermediate-range strike campaign against Russian logistics and electronic warfare paved the way, the think tank said.

Drones have made this front so deadly that armor now mostly fights from kilometers back. That is what makes Ukraine's armored push onto fortified positions near Lyman stand out. Russia has already shifted its effort south toward Sloviansk after losing the Lyman pincer.

Armor reached Russian bunkers without drawing drone strikes

To break the strongest Russian fortifications, Ukraine used old Soviet BTR-60 armored personnel carriers rebuilt as remote-controlled explosive vehicles, the 3rd Army Corps says.

Ukrainian forces drove them up to heavy Russian fortifications without coming under Russian drone strikes, ISW noted. The think tank said this indicates Ukraine neutralized or otherwise negated Russia's drone defenses in the area.

Strikes on fuel starved Russia's jammers

Ukraine achieved tactical drone overmatch through extensive shaping operations and an intermediate-range strike campaign, ISW said. Those strikes targeted the Russian drones and electronic warfare (EW) systems that would otherwise have hunted the advancing vehicles.

The 3rd Army Corps reported on 17 September that strikes on Russian logistics in occupied Luhansk Oblast had degraded Russian fuel supplies to the front, ISW wrote that day. The corps said that strained Russia's ability to use drones and EW against Ukrainian drones. EW systems consume a lot of power, and Russian troops run them on diesel generators, ISW explained.

Deputy corps commander Maksym Zhorin credited strict information silence and a "Protective Drone" system of EW assets, according to the same assessment. He said it helped neutralize around 20,000 Russian drones. The corps had earlier described mapping Russian command posts and striking them to sow panic.

Five settlements and 2,000 Russian losses

The corps liberated Nove, Ridkodub, and Katerynivka and restored control over Karpivka and Novomykhailivka, it said on 28 September. The phase added 51 km², bringing the total since the offensive began to 176 km².

Russian losses reached 2,000 personnel, and more than 250 Russians were taken prisoner, according to the corps. Corps commander Andrii Biletskyi said a feint from Shandryholove toward Zelena Dolyna drew Russian reserves away from the real target, Nove.

The first two phases had reportedly cleared more than 125 km² north of Lyman.

Ukraine's 3rd Army Corps has defeated Russia at the key settlement of Nove in Donetsk Oblast by pointing it the wrong way. Russia has poured its reserves into counterattacks on a feint axis and "slept through" the real strike, which took the important hub in the village and closed the decisive third season of the Vivaldi offensive, commander Andrii Biletskyi said.

Vivaldi is Ukraine's counteroffensive aimed at disrupting Russian forces' plans to encircle the fortress-belt cities in Donetsk Oblast from the north and south. Among them are Sloviansk, Kramatorsk, Druzhkivka, and Kostiantynivka. These cities have helped hold back Russian forces since 2014.

Over its first two "seasons," the 3rd Army Corps and attached units have retaken more than 125 square kilometers, half of it de-occupied outright, and inflicted more than 3,000 casualties on Russian forces.

The operation in Nove was its "third season," Biletskyi said, the turning point of the whole operation. The corps liberated Nove, Ridkodub, and Katerynivka and restored control of Karpivka and Novomykhailivka, adding 51 square kilometers, bringing the total liberated since the offensive began to 176. Ukrainian forces have taken 250 Russians captive.

The feint drew Russia's reserves

The victory, by Biletskyi's account, was won by deception.

"The enemy was convinced the main direction of the strike was Shandryholove–Zelena Dolyna," he revealed, and it burned its reserves counterattacking there.

He added that the Russians slept through the real strike, which was concentrated on taking Nove. The village was the prize, a key Russian hub on the bridgehead, ringed by heights that command the surrounding ground.

"Who controls the heights holds the initiative," Biletskyi said.

By spending its reserves on the wrong axis, he suggested, Russia had little left to hold Nove when the real assault arrived.

Old APCs crack the defense

To break the strongest fortifications, the corps said, it used a homemade weapon: Soviet BTR-60 armored carriers converted into remote-controlled kamikaze robots, driven into Russia's toughest positions and detonated.

In 2024, the Ukrainian forces received another local upgrade of the post-Soviet BTR-60 wheeled armored personnel carrier. This time it was fitted with the BM-7 "Parus" turret, known from the BTR-4 "Bucephalus" The main armament consisted of a 30 mm ZTM-1 automatic cannon paired with a 7.62 mm KT-7.62 universal machine gun.

Additional armament might include a set of four anti-tank guided missile launchers mounted on the sides, or two launchers and a 30 mm KBA-117 automatic grenade launcher. As a result, this upgraded BTR-60 saw a significant improvement in firepower, although the vehicle still has very weak armor and less-than-optimal access to the troop compartment.

It was the latest of the corps' robotic improvisations in Vivaldi, which have included air-dropped ground drones and Bullspike grenade-launcher-armed UGVs. They are Bulgarian hand-held, rocket-propelled anti-tank grenade launchers based on the Soviet RPG-22, which the Bulgarian defense industry previously produced under license.

The corps has leaned on such machines throughout the operation to keep its infantry out of the deadliest fights.

Whole units surrender

As the defense broke down, Russians gave up in groups, including officers, pilots, and artillery soldiers, the corps said. The 3rd Assault Brigade carried much of the fighting, while the 3rd Border Guard Detachment, named for the fallen Colonel Yevhen Pikus, retook Ridkodub and dug in on the new line, with the 10th Mobile Border Guard Detachment "DOZOR" taking an active part in the assault.

The Institute for the Study of War (ISW) published a map in its analytical report on 24 September that contrasts the claimed Russian encirclement with the location of Russian forces as assessed by the experts. Based on the evidence observed by ISW, the nearest area where Russian forces are present is 10.2 kilometers from the southeastern outskirts of Dobropillia.

Russia has been spreading disinformation about its successes around Dobropillia as part of what ISW calls a cognitive warfare effort to portray Ukrainian defenses as on the verge of collapse. Russia's Defense Ministry published a map claiming the city was surrounded. ISW's own map challenges it. The Ukrainian military says the city remains under its control.

Russian Defense Ministry claims it is already destroying encircled Ukrainian troops in Dobropillia and moving further

Units of Russia's Center Grouping of Forces continue combat operations against encircled Ukrainian forces in the Dobropillia area of Donetsk Oblast while simultaneously advancing toward Oleksandrivka, the Russian Defense Ministry claimed. ISW analysts, meanwhile, said they have not observed evidence supporting Russia's claim that the city is encircled. They also noted that Ukrainian officials "directly refute" the claim.

ISW observed evidence that Russian infiltrators, small groups, were operating east and northeast of Dobropillia on 19 and 20 September. The institute did not assess that these infiltrators had consolidated their positions.

Ukrainian forces maintain positions south and northeast of Dobropillia, military observer Kostiantyn Mashovets said on 20 September, according to ISW.

Russian forces have not made major gains in the Dobropillia direction, the chief of staff of an artillery reconnaissance battalion said on 22 September, according to the institute. On the same day, a Russian milblogger described the "alleged Russian encirclement of Dobropillia" as potentially meaning not the direct presence of infantry, but only the establishment of fire control over Ukrainian logistics, including roads west of Dobropillia and toward Sviatohorivka, according to ISW.

ISW noted that Russia's pervasive military culture of lying—what Russian milbloggers themselves call "beautiful reports"—has degraded the Defense Ministry's own ability to understand the battlefield and enabled inflated claims like the Dobropillia encirclement.

Russia uses this disinformation as a "diversion"

In its statement, the Russian Defense Ministry itself described Dobropillia as a "strongly fortified settlement" whose seizure would threaten key Ukrainian supply lines running from Dnipropetrovsk Oblast toward the Fortress Belt—the Sloviansk-Kramatorsk-Druzhkivka urban agglomeration.

Russia has recently renewed its attempts to break through toward Dobropillia.

Third Army Corps Commander Andrii Biletskyi said that Russian forces sought to bypass the fortified cities through Dobropillia and link up with troops advancing from north of Lyman, rather than launch a direct assault. ISW noted on 16 September that the Vivaldi operation disrupted Russia's two-pronged plan. In its 24 September report, ISW said Russia's claims about Dobropillia were partly intended to divert attention from Ukraine's elimination of the Russian salient north of Lyman, which has likely forced Russia's command to rethink its wider encirclement plans.

Ukraine's Third Army Corps says it became the first military unit in the world to use ground robots for mine clearance inside a live offensive, sending the machines ahead of its infantry into the deadliest sectors to keep soldiers out of the line of fire, Censor.NET reported. The corps built the capability from nothing during its Operation Vivaldi counteroffensive in Donetsk Oblast.

Keeping soldiers alive has become the organizing principle of how Ukraine fights, and handing the jobs most likely to kill them to ground robots is how an army that refuses to treat its people as expendable defends the line.

Robots cleared 30 km of routes in two nights

On the Shandryholove axis, the robots cleared 30 kilometers of routes in two nights—work that two companies of sappers would have needed a full week to finish. The corps reported no losses among its sappers there. Announcing the operation's second phase, corps commander Brigadier General Andrii Biletskyi said protecting personnel drives how his troops plan and fight:

"People often ask, but what about our losses? My answer: we minimize them by every possible means. In assault operations, drones and ground robots always move ahead of the infantry," he said.

Robots clear most of the mines and mine Russian routes in return

The corps says it built the system from scratch and scaled it from a single squad up to the entire corps, arguing that manual clearing would be impossible across open terrain swept by fire. Ground robots now lift roughly 60% of the anti-personnel mines in its area of responsibility. They also work in reverse, remotely mining Russian advance routes—one crew can lay up to 200 meters a day, cutting off enemy reserves. The same machines carry frontline logistics, evacuating the wounded and hauling in provisions and equipment.

Operation Vivaldi continues in Donetsk Oblast, where the corps recently air-dropped robots behind Russian lines. Its advance has disrupted Russia's plan to encircle the fortified belt of Donetsk cities. In the second phase, the Third Army Corps liberated Shandryholove and Derylove and took full control of Drobysheve. Across the operation's first two phases, it has retaken 125 square kilometers.

Ukrainian partisans say they have sabotaged the railway signaling that keeps Russian troops supplied on the Lyman front. The ATESH movement reports that its agents disabled four relay cabinets on a line through Voronezh Oblast that carries military cargo to Russian forces there, delaying ammunition to three regiments.

The strike was timed to help Ukraine's Operation Vivaldi, the counteroffensive the Third Army Corps is running near Lyman in northern Donetsk. In its first phase, the operation cleared 75 square kilometers of Russian infiltrators and de-occupied another 10.

Cutting the rail line that feeds the Russian units facing that offensive is, by ATESH's account, part of the same fight, targeting the supply line rather than the front.

Four cabinets go dark

The sabotage hit a rail corridor running through the Voronezh, Novovoronezh, Liski, and Ostrogozhsk areas of Voronezh Oblast, a route ATESH says Russia uses to move military cargo toward the Lyman axis.

Relay cabinets house the switching gear that runs a line's automatic signals. Knocking them out can freeze traffic on a stretch of track without a single explosion, and ATESH says its agents disabled four of them. As with the movement's other claims, the account could not be independently verified.

Ammunition backs up

By ATESH's telling, the signaling failure delayed shipments of ammunition and engineering materiel to the 1st and 15th Guards regiments and the 254th Motor Rifle Regiment. Russian commanders, it said, had to rush in repair crews and divert resources to guard the infrastructure. A delayed shipment, far behind the front, can be felt at it, where an assaulted position waits for the ammunition that does not arrive.

ATESH hunts the supply lines

ATESH is a network of pro-Ukrainian agents operating inside Russia and Russian-occupied territory, and it has increasingly gone after the rail and power infrastructure that sustains Moscow's war. This month, the group also said it knocked out the power supply of a plant in Voronezh that makes components for Russian missiles.

Ukraine's Vivaldi counteroffensive rolled back a Russian advance north of Lyman in Donetsk Oblast. However, Moscow shifted part of its forces south, Roman Pohorilyi, co-founder of the Ukrainian battlefield mapping project DeepState, told Radio NV. Russian troops are now infiltrating Mykolaivka, a key strongpoint on the approach to the fortress city of Sloviansk, Pohorilyi said.

The halted advance was one arm of Russia's plan to encircle Ukraine's Donetsk fortress belt—the fortified cities of Sloviansk, Kramatorsk, Druzhkivka, and Kostiantynivka. Pohorilyi warned that losing Mykolaivka would create serious problems for Sloviansk's defenders. Russia is still pressing toward Dobropillia on the belt's southwestern flank.

Pohorilyi said Russia formed a "claw" north of Lyman by exploiting Ukrainian brigades short of personnel and pushing small groups into their lines. Ukraine's Third Army Corps stabilized the area, built up forces, and counterattacked. The push "multiplied all [Russia's] previous efforts by zero," he said.

Russian forces had repeatedly tried to capture or bypass Lyman, Pohorilyi said. Russian groups still infiltrate the approaches to the city, although Ukrainian forces have stabilized the situation there.

The corps says Vivaldi's first two phases regained control of 125 square kilometers, including 50 that had been under Russian occupation. It reported liberating Shandryholove and Derylove, securing Drobysheve, and inflicting more than 3,000 Russian personnel losses. Those battlefield figures have not been independently verified.

Pohorilyi noted that the area around Mykolaivka had, until recently, been under the responsibility of Ukraine's 11th Army Corps and is now under the Third Army Corps.

Ukrainian troops must now find and stop infiltrating Russian groups before they establish control, he said. Personnel shortages on the Lyman axis persist, although he said reinforcements are being distributed more evenly.

Operation Vivaldi and the wider fight for Donetsk's fortress belt

The Third Army Corps first disclosed Operation Vivaldi on 15 September after conducting the counteroffensive north of Lyman under information silence. Commander Andrii Biletskyi said the announced gains were only the first phase; the corps said its attacks had disrupted Russian supply routes.

A 60th Mechanized Brigade captain said Ukrainian units quietly assembled near Derylove and Drobysheve, then struck Russian drone launch sites at planned times so infantry could advance. The corps disclosed a second phase on 20 September.

Farther southwest, Dobropillia faces even heavier pressure, Pohorilyi said. Russia has concentrated large forces there and is pushing with relentless infantry across a wide front, backed by thousands of drones each month—reconnaissance, strike, FPV, and Lancets—with numbers still rising. Russian troops are moving on settlements south of Dobropillia to establish a strongpoint and push deeper into Donetsk Oblast.

The pressure is not new: Biletskyi said Ukrainian troops halted a Russian incursion there last year. After Moscow claimed on 22 September to have encircled the town, the Institute for the Study of War found no evidence to support the claim.

Ukraine's Third Army Corps dropped kamikaze ground robots on Russian command nodes identified by reconnaissance during Operation Vivaldi, a corps intelligence officer told Radio NV. The strikes aimed to break command coordination and force Russia to divert combat troops to guard its own headquarters, while a parallel campaign destroyed a diesel pipeline that fed about half the daily fuel needs of Russia's entire West grouping.

Russia's full-scale war against Ukraine is now in its fifth year, with Moscow pushing simultaneously along the front and striking cities behind it with drones, cruise and ballistic missiles, and glide bombs. The Vivaldi operation is the first time Ukraine has publicly shown how a reconnaissance-to-robot strike chain works against command nodes without risking infantry, a method that could be replicated across other sectors where Russia's coordination depends on forward headquarters within drone range.

Reconnaissance identified command nodes, robots hit them

One of the tasks set by corps commander Brigadier General Andrii Biletskyi was to disrupt command and communications in the Russian chain of command, the officer said. Brigade and corps reconnaissance identified areas where a strike could break Russian control.

"Reconnaissance of the brigades and the corps identified such areas that could affect the disruption of enemy command. It was into these areas that robots were dropped to create panic, disrupt command, and prevent the enemy from being effective," the officer told Radio NV.

To protect their command posts from the robots, Russian forces had to pull in additional personnel—troops that could not then be used to resist the Third Corps' ground assault.

The Third Corps announced on 20 September that heavy bomber drones delivered kamikaze ground robots more than 10 km behind Russian lines, calling it a world first.

Ukraine is saving Donetsk Oblast with world’s first-of-its-kind operation: Vivaldi counteroffensive drops robots directly from heavy bombers 10 kilometers behind Russian lines

The same intel operation identified a frontline diesel pipeline

The same intelligence operation uncovered a pipeline running from Voronezh Oblast to temporarily occupied Luhansk Oblast. The pipeline carried finished diesel, not crude oil, and supplied about 50% of the daily fuel needs of Russia's forces on the direction, the officer said.

The corps struck both the intake point where fuel entered the pipeline and the output point where it was loaded onto tankers. The strikes forced Russia to dismantle the pipeline entirely. Russian forces now truck fuel from Voronezh Oblast, a 400 km supply run.

Ukraine’s Donetsk counteroffensive wins not by force but by stealth: it gathers troops under Russian nose and seizes two villages before they react

The pipeline's destruction affected not just the Lyman direction but the entire West grouping, including the Kupiansk and Borova directions, the officer said. The logistical disruption left frontline Russian drone units unable to refuel generators to charge batteries, and electronic warfare systems had to operate in a reduced mode.

Repair bases struck, 250 km logistics detour

Third Corps intelligence also located the repair base of Russia's 20th Army and its 144th Division. Ukrainian strikes during the preparatory phase forced Russia to relocate the base to Voronezh Oblast, increasing the repair route to 250 km.

Russia's 20th Army and its 144th Division, reinforced by assault detachments from the First Tank Army, remain the main strike force on the Oskil-Sviatohirsk direction, the officer said. The First Tank Army has been sending additional assault units to stabilize the Russian defensive line after Vivaldi, but these reinforcements are taking critical losses on logistics routes before reaching the combat zone.

Rubikon pulled out, Russian drone units at 70–90% strength

The officer said the corps headquarters specifically targeted Russia's most effective drone formations. During the preparatory phase, the elite Russian drone unit Rubikon was identified as a critical threat that could isolate the area of operations and obstruct Ukrainian maneuver.

Ukrainian reconnaissance located and passed targeting data to strike assets. Rubikon suffered heavy losses in equipment and personnel, and a senior Russian commander—misjudging the Third Corps' offensive potential—pulled the unit to rear areas for recovery at what turned out to be the worst possible moment, just as Ukraine's assault began.

Ukraine retakes ground in a region Russia has fought for years to capture. “Vivaldi” is only getting started but is already “one of the most important victories for Ukraine in 2026”

Russian drone units on the direction are now staffed at 70–90%, the officer said. The corps is working to degrade their capability through targeted strikes on launch sites, pilot positions, and logistics in the second and third echelons.

Four seasons, two public

The officer said Russia's current task is to stabilize its defensive line, restore its observation network, and bring in additional reserves for counterattacks. Russia does not have enough personnel and will have to pull troops from training grounds before they finish their courses, shortening training cycles.

Ukraine’s Vivaldi operation cleared 85 square kilometers near Lyman. A soldier who fought it says one thing was hardest of all

Operation Vivaldi has at least four "seasons," of which only the first two have been made public. The operation's name refers to Italian baroque composer Antonio Vivaldi, and The Four Seasons is his best-known set of four violin concerti.

Biletskyi confirmed the liberation of Shandryholove, Derylove, and full control over Drobysheve on 20 September, bringing the total to 40 km² of freed territory in the second season alone. Russian losses have reached an estimated 3,000 personnel overall, over 12,000 drones in the first season, and hundreds of vehicles, according to the Third Corps. ISW assessed that the operation disrupted Russia's plan to encircle the fortress belt of Donetsk cities—Sloviansk, Kramatorsk, Druzhkivka, and Kostiantynivka.