Ukraine's Defense Forces advanced more than 15 km through underground utility tunnels into Russia's rear on the Kupiansk axis in Kharkiv Oblast, the Khartiia Corps of Ukraine's National Guard reported on 22 October. The corps called it Operation Veles. The underground advance was paired with attacks on the surface and drone strikes, hitting Russian forces from two directions, the corps told Militarnyi.

Russian troops have repeatedly crawled through gas pipelines around Kupiansk to get behind Ukrainian lines, even after Ukraine reported confident control of the city in February. This time, Ukraine went underground itself. The operation took away Russia's chance to get into Kupiansk's rear, the corps said.

The corps reported more than 30 Russian soldiers captured and Russian losses of more than 100. Militarnyi, citing the unit, put the number of Russian troops killed at over 100.

Khartiia studied how Russian troops moved through pipes before going underground itself, the corps commander, Brigadier General Ihor Obolenskyi, said.

"We watched how the enemy works underground and studied how they do it. The Russians intended to use gas pipelines to get into the rear of our troops. So we went underground ourselves. We anticipated the enemy's actions and mastered the tactics of underground combat," he said.

For the operation, troops trained physically and psychologically to fight in confined spaces, sappers and engineers prepared the underground route, and special communications, navigation, silent logistics, and life-support systems were put in place, Khartiia told Militarnyi. The operation was named after Veles, the Slavic pagan god of the underworld.

Khartiia's brigade, the R.U.H. assault regiment, the Lava drone regiment, the Achilles drone brigade, and units of Ukraine's military intelligence, including the Freedom of Russia Legion and the Russian Volunteer Corps, took part, the corps said.

Russia has used pipelines to infiltrate before

By September 2025, Russian forces had used pipelines to move troops behind Ukrainian lines three times, Ukrainian monitoring project DeepState reported on 12 September 2025. The first was in Avdiivka, the second near Sudzha, and the third near Kupiansk, where groups crossed the Oskil River through a gas pipe.

Near Sudzha in March 2025, Russian special forces walked through a pipeline that until recently had carried Russian gas to Europe, the Associated Press reported. A pro-Kremlin blogger claimed they covered about 15 km and that some spent several days inside.

Russian troops kept using the pipeline near Kupiansk this year. On 27 September, Khartiia's reconnaissance drones recorded Russian forces leading nine civilians, including children, elderly people, and a person on crutches, through the gas pipeline out of the Kupiansk community. Men of military age in civilian clothes walked alongside them, and the corps believes they were Russian soldiers using the group as cover to withdraw. Ukrainian troops held fire because of the civilians, the corps said, adding that the case has been documented for a war crimes investigation.

Why the war is moving underground

Drones, constant surveillance, and AI-assisted targeting have made the battlefield surface transparent and deadly, argue John Spencer, chair of urban warfare studies at West Point's Modern War Institute, and Col. Drew Craig, principal military engineering staff officer at NATO's Allied Rapid Reaction Corps. In an August analysis, they write that soldiers in Ukraine describe a "death zone" of some 30 km, where moving above ground can draw an attack within minutes. When firepower makes the surface too dangerous, armies have historically gone underground, as they did in World War I and Vietnam, and more recently in Gaza and Lebanon.

"Armies that cannot survive above ground must adapt below it," the authors write.

Fighting in tunnels brings its own requirements, the authors write: detecting the enemy by sound and vibration, and specialized unmanned systems that cannot rely on GPS or stable radio links. Long stretches underground also take a severe psychological and physical toll on soldiers.

Western militaries are not ready for this, Spencer and Craig write. No NATO partner maintains even general capabilities for large-scale underground warfare, and US and British efforts focused mainly on detecting and clearing tunnels rather than occupying and operating in them.

Ukrainian infantry encircled and retook the village of Kolodiazi north of Lyman without getting drawn into street fighting, while a drone battalion kept the sky above them shut, the battalion’s chief of staff told Suspilne on 18 October. The village fell during the fourth and final phase of Operation Vivaldi, Ukraine’s counteroffensive in northern Donetsk Oblast.

For years now, Russia has aimed to seize Lyman and cross the Siverskyi Donets River. It needs this area to encircle Ukraine’s fortress belt of Donetsk Oblast cities from the northwest, ISW assesses. Vivaldi’s four phases retook 277 km² and 16 settlements on that approach, and a veteran of the operation has said Ukraine’s assault troops suffered more than ten times fewer casualties than Russian forces doing it.

Drones over the infantry

The 60th Mechanized Brigade fought in all four phases of Vivaldi and took Kolodiazi in the last one, said the chief of staff of the brigade’s Fatum unmanned systems battalion, callsign Krash.

“Our task, as an unmanned systems battalion, was to escort and ‘close’ the air in front of our infantry to make it impossible for the enemy to hit it. To suppress all the firing assets possible,” he said.

The brigade’s 3rd Mechanized Battalion, the main striking force, encircled Kolodiazi and retook it without getting drawn into street fighting, Krash said. The 1st Mechanized Battalion kept Russian reinforcements out of the area, while drone crews suppressed artillery, hit supply runs, and worked against Russian drone operators.

Explore further

Vivaldi counteroffensive advanced after Ukraine took Russia’s drones out of the fight, ISW assesses

500 troops and 200-plus vehicles

The drone battalion killed or wounded about 500 Russian troops during the fourth phase and struck Russian armored vehicles, trucks, and motorbikes, its chief of staff said.

“More than two hundred pieces of various equipment: Grad and Uragan multiple rocket launchers, various armored vehicles, tanks, armored combat vehicles. Most of all motorbikes and quad bikes, there the count runs into the hundreds. This is our enemy’s main logistics tool,” he said.

Ghost villages

The villages retaken in northern Donetsk Oblast are nearly empty of civilians, Krash said.

“It’s very typical for de-occupied settlements: these are ghost towns. You can see right away where the occupier stepped. All the settlements are under the control of the Third Army Corps, our forces stand there and prevent enemy infiltration. But civilian life in these towns is either absent or very scarce,” he said.

Third Army Corps commander Brigadier General Andrii Biletskyi reported Kolodiazi’s liberation, along with Zelena Dolyna and Lypove, when he summed up Vivaldi’s fourth phase, which secured 101 km².

Ukrainian forces are advancing east of Sloviansk and Kramatorsk, and even Russian milbloggers now acknowledge it, the Institute for the Study of War (ISW) said on 8 October. The gains may follow months of groundwork like the one that preceded Operation Vivaldi near Lyman, which Ukraine says returned 176 km² to its control. Russian commentators are already doubting that Moscow can reach the two cities.

Russia's years-long push on the Fortress Belt, the chain of cities anchoring Ukraine's defense in Donetsk Oblast, has been stalling since Vivaldi began. Unable to take those cities, Russia keeps hitting them from the air. On 8 October, a Russian bomb killed 30 people on two buses in Kramatorsk.

Across the Siverskyi Donets

Russian milbloggers said Ukrainian forces liberated Ozerne and advanced east of Pyskunivka toward Kryva Luka, ISW reported. They also acknowledged that Ukrainian troops drove Russian forces out of Pyskunivka. Ukrainians are now counterattacking toward Kryva Luka from the west and northwest, from across the river.

Explore further

Vivaldi counteroffensive advanced after Ukraine took Russia’s drones out of the fight, ISW assesses

ISW called the repeated Russian claims of a river crossing notable, because the Siverskyi Donets is a significant natural obstacle. Kryva Luka is a dominant height just south of the river. From there, Ukraine could launch further counterattacks. Ukrainian forces appear to have pushed Russian troops off both banks in this area, ISW assessed.

The heights Russia wanted

After Vivaldi cleared ground near Lyman in September, Russia shifted its push south toward Mykolaivka and Sloviansk. Russian forces likely see Mykolaivka, just east of Sloviansk, as a primary objective, ISW said. Its heights would favor an offensive on the city. Ukrainian pushes northeast and southeast of the town now deny Russia that terrain.

East of Kramatorsk, milbloggers claimed Ukrainians liberated Malynivka and advanced between Fedorivka Druha and Holubivka. They also reported gains into southern Minkivka and near Fedorivka. The lines remain tangled. Geolocated footage shows Ukrainian forces striking a Russian position in central Tykhonivka after what ISW assesses was a Russian infiltration.

ISW said the counterattacks may point to a broader Ukrainian goal: pushing Russian forces east, away from the Sloviansk–Kramatorsk area and toward the Siverskyi Donets–Donbas Canal.

The Vivaldi playbook

The counterattacks have run for weeks. On 29 September, Ukrainian military observer Kostiantyn Mashovets reported them in the same areas, saying Russia's 3rd Combined Arms Army had failed to make significant gains. ISW assesses that the attacks build on months of shaping meant to wear down Russia's offensive capacity.

Explore further

Vivaldi’s secret weapon was the targeting, not the robots: Third Corps reconnaissance mapped Russian command nodes, then hit them to cause panic

Before Vivaldi, Ukrainian forces targeted Russian drone operators, gaining drone superiority before the counteroffensive. They used the same approach ahead of their Oleksandrivka counterattacks in early 2026.

Moscow appears to see the pattern. A Ukrainian military official said on 7 October that Russia is moving drone units and Spetsnaz from quieter sectors to the Sloviansk–Kramatorsk direction. Ukraine also reorganized its command in and around Donetsk Oblast in early September, which may be blunting Russian attacks from the east, ISW said.

"Distant" and "doomed"

One Russian milblogger called an advance toward the Sloviansk–Kramatorsk area a "distant" prospect, ISW reported. A Russian offensive from Siversk toward Sloviansk may be "doomed" to failure or heavy losses unless Russia retakes the forests south of Lyman, he said.

The counterattacks east of the two cities appear to support Vivaldi, ISW assessed. Together with Russia's defeat north of the river, they could disrupt Russia's offensive toward Sloviansk from the east entirely.

If Ukraine holds Kryva Luka and keeps Russia off the Mykolaivka heights, Moscow's pincer on Sloviansk and Kramatorsk loses the ground it was built on.

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.

Explore further

Ukraine’s Vivaldi counteroffensive disrupts Russia’s plan to encircle Donetsk Fortress Belt – ISW

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.

Explore further

Russia’s mass drone attacks on Ukraine have a goal—likely Ukraine’s capitulation by spring 2027, ISW says

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.

Within 24 hours of claiming Ukrainian troops were surrounded near Dobropillia, Russia’s Defense Ministry and pro-war channels expanded the narrative to several supposed encirclements in northern Kharkiv Oblast. Evidence supports none of that, the Institute for the Study of War (ISW) has said.

The claims come as Ukrainian forces make gains in several frontline sectors, according to ISW. Near Dobropillia, Russian bloggers described the ability to fire on supply roads rather than troops surrounding the town. At the same time, Ukrainian forces said they had prevented Russia from physically cutting the routes.

Russia’s Defense Ministry claimed its forces had captured Krasnyi Yar and Potykhonove northeast of Kharkiv. Pro-war bloggers then claimed Russian troops threatened to trap Ukrainian units near Riznykove and had already surrounded others near Rublene. One asserted that roughly 1,500 Ukrainian soldiers were encircled across 460 square kilometers.

ISW found no evidence for those claims. A Ukrainian brigade spokesperson said Russian forces were still shelling settlements they claimed to hold and described positions in the area as heavily intermingled, with no clear front line.

Around Dobropillia, the Kremlin-linked Rybar channel claimed Russian troops were infiltrating toward nearby settlements and making tactical gains south of the town. It did not claim Russian forces had secured those settlements or show an encirclement on its map, ISW noted.

Another Russian blogger said neither side currently had the forces needed to establish and sustain a genuine encirclement.

Russia’s push toward Dobropillia continues

Russia’s Defense Ministry had claimed on 22 September that its troops surrounded Dobropillia, a transport hub on the approach to Ukraine’s fortified cities in Donetsk Oblast.

ISW found no evidence for that claim and linked its timing to the UN General Assembly and Ukraine’s recent battlefield gains. A Ukrainian officer said Russian troops had made no major advances near the town.

Russian assaults continue despite that setback. A Ukrainian staff sergeant reported a sharp increase in the number of small groups trying to reach Dobropillia. On 23 September, Ukraine’s 1st Azov Corps said its forces had prevented Russian troops from physically cutting supply routes toward Dobropillia and Druzhkivka.